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Weather Station Hardware => Blitzortung => Topic started by: dfroula on August 15, 2013, 07:08:48 PM

Title: My home-made ferrite antennas
Post by: dfroula on August 15, 2013, 07:08:48 PM
Here are some photos of my home-made ferrite antennas.

I found a source for some 7.5mm x 50mm ferrite rods with an initial permeability of 2000u - ideal material for a ferrite antenna, but too short to be of practical use. However, the price was very cheap! I ordered 32 of them to experiment with. I decided to try to make some 7.5mm x 250mm cores by gluing 5 of the smaller rods end-to-end. Gluing ferrite in this manner is an accepted practice and has a very small effect on the inductance of the final antenna.

Richo suggested that close-winding a single layer of AWG26 enameled wire on a 10mm x 200mm core, leaving 5mm unwound at the ends, would produce a ferrite antenna with outstanding performance. I figured that a 7.5mm x 250mm rod would be equivalent.

Here is a photo of the 50mm rods and the "Super-thick" commercial grade cyanoacrylate glue I used to assemble the longer rods. The salt shaker is not a part of the procedure!
(http://projectmf.homelinux.com/station_pics/Ferrite_1.jpg)

One drop in the center of the rod is enough.
(http://projectmf.homelinux.com/station_pics/Ferrite_2.jpg)

I used a piece of aluminum channel clamped into a table vice and lined with waxed paper to align the rods as they were glued together. The waxed paper prevents sticking to the aluminum. 30 seconds of pressure was applied to allow the glue time to set.
(http://projectmf.homelinux.com/station_pics/Ferrite_3.jpg)

The third rod ready to be glued...
(http://projectmf.homelinux.com/station_pics/Ferrite_4.jpg)

The final 250mm assembly of 5 rods. I allowed 30 minutes before removing the assembly from the channel. I allowed another 2.5 hours for the glue to fully cure before winding the cores.
(http://projectmf.homelinux.com/station_pics/Ferrite_5.jpg)

This photo shows the first finished antenna. The cores were wound with 26AWG enamled copper wire. I used electrical tape to secure the ends and sections of the coil as I wound to prevent unraveling and to keep the windings tight. When I reached the far end, I loosely wound the free end back to the other end. This is the end of the coil that will be connected to ground, following the example of the commercial antenna provider.
(http://projectmf.homelinux.com/station_pics/Ferrite_6.jpg)

A close-up of the finished first antenna and extra cores...
(http://projectmf.homelinux.com/station_pics/Ferrite_7.jpg)

The second antenna completed and the two additional cores for a second antenna pair.
(http://projectmf.homelinux.com/station_pics/Ferrite_8.jpg)

A close-up of the two completed antennas.
(http://projectmf.homelinux.com/station_pics/Ferrite_9.jpg)

I slipped the antennas into foil-covered and grounded 3/4" PVC conduit sections with a longitudinal gap in the foil to prevent shorting the magnetic field. These things have incredible gain! I am still testing, but they appear to be giving my high-gain flat-panel loop some serious competition!
Title: Re: My home-made ferrite antennas
Post by: miraculon on August 15, 2013, 07:32:08 PM
Thanks for sharing the info. It doesn't look all that difficult to put together.

Where did you get the ferrites?

At this point, the start of winding is obvious, but did you identify it for phasing after is is in the PVC conduit? Did you shrink-wrap them like the ferrites that came from Germany?

When you get them running on your detector, it would be great to know how they compare with the flat panel.

Greg H.

Title: Re: My home-made ferrite antennas
Post by: dfroula on August 15, 2013, 07:40:52 PM
Up and running now! http://projectmf.homelinux.com:8081 to see them in action (use Chrome to avoid scrambled display). Check the stats on lightningmaps.org, station 681.

They look to perform as well or better than my 52-turn flat panels, based on the last 60 minutes of detections.

I have not shrink-wrapped them yet. I may just use electrical tape.

I made a nice housing similar to yours, Greg, with the conduit "L" box and 3/4 inch PVC conduit, covered in aluminum foil with the slit.

Don
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 15, 2013, 07:55:10 PM
I bought the ferrites here. Be sure to order the 2000u, 7.5mm x 50mm rods.

http://www.surplussales.com/Inductors/FerRods/FerRods.html

.75/ea for the 32 I bought! Dirt cheap. 2000u material is next to impossible to find.

I had them 3 days after ordering.

Don
Title: Re: My home-made ferrite antennas
Post by: DanS on August 15, 2013, 08:08:10 PM
Do you know the number of turns you ended up with?  I've been doing similar things here, playing with various tank circuits and ferrite antennas to get different gain results. TIA

Dan
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 15, 2013, 08:33:46 PM
Well, I used 26AWG enameled wire with a total winding length of 240mm. .42675mm thick, including insulation.

That would be 563 turns, 7.5mm diameter.

563 * 7.5 * Pi = 13528.65mm of wire or 522 inches of wire (43.5 feet).

Don
Title: Re: My home-made ferrite antennas
Post by: DanS on August 15, 2013, 08:35:41 PM
thks!
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 16, 2013, 01:15:01 PM
I tried a 1" drop test on the glued cores. Every joint fractured. The cyanoacrylate is NOT a good choice for gluing these rods. The assembly would be far too fragile and subject to undetected breaks.

I'll repeat the procedure this weekend using 15 minute 2-part epoxy.

Regards,

Don
Title: Re: My home-made ferrite antennas
Post by: Beaudog on August 16, 2013, 01:55:16 PM
The cores look to be hollow. I would run a wooden dowel thru them prior to gluing (they might not even need gluing)them together this should make them considerably stronger and less prone to break.   I don't think it would have any if much effect on their Q.
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 16, 2013, 02:39:25 PM
No, the cores are solid.
Title: Re: My home-made ferrite antennas
Post by: wxman44 on August 16, 2013, 05:45:11 PM
If you were to shrink wrap the cores for strength prior to winding them, would that significantly impact performance?
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 17, 2013, 09:21:56 AM
That is an excellent idea. I re-glued the cores with epoxy last night after cleaning up the ends with alcohol. The joints seem strong, but I have the feeling that ANY glued joint is going to be inherently weak. Ferrite is a powder mixed into a binder. The brittle composite nature of ferrite does not have enough strength to support the glued joint.

There is sufficient strength to support winding the coils, but shear strength is low. Pre-wrapping the cores with shrink wrap would stabilize the glued joints laterally. In addition, spacing the windings away from the core should minimize the distributed capacitance and self-resonance.

Darn, the long pieces of shrink wrap I have are just a hair to small to get the 7.5mm rods through. Off to Lowes!

Best,

Don

If you were to shrink wrap the cores for strength prior to winding them, would that significantly impact performance?
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on August 17, 2013, 09:57:33 AM
There are specially adapted epoxies for gluing ferrites. Google it.
Title: Re: My home-made ferrite antennas
Post by: miraculon on August 17, 2013, 10:34:45 AM
I was wondering whether J-B Weld would work for this...

 :-k

Greg H.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on August 17, 2013, 11:39:54 AM
Got my kit of parts yesterday.  My youngest son was ecstatic since it came in a German language box with a cool clock on it. 

He was crushed when I opened it.  Now I'll have to come up with some sort of consolation prize for him.

I'm very happy.

Nonetheless, IF one could find shrink tubing just the right size to get the cores in, why not put the assembly together without any glue at the joints at all, slightly compress the whole stack and then shrink the tube assembly?  No glue, tightly held, and apparently the function of a rod built up from many pieces, as long as the ends are in close approximation, don't need any sort of fixation to conduct the magnetic lines through them, and glue is superfluous to function.

JB Weld might be stronger, but then again the problem is that cores are inherently fragile already, and to expect the last few millimeters of a compressed substance to hold tight is really asking a lot.  I'm still interested in the idea of using a dremel or such to make a little dimple or 5mm hole into the rod so that a load capable glue like epoxy can get more area of purchase to adhere to and distribute the load from the rod next to it through more of an area than just those smooth surfaces.

Darn, I should have ordered MORE of those rods when the order went in.



Title: Re: My home-made ferrite antennas
Post by: dfroula on August 17, 2013, 12:44:52 PM

Yep, I agree completely! The shrink wrap alone would likely be fine.

I just wrapped each epoxied joint tightly with electrical tape, rewound the cores, wrapped the assembly in thin foam packing and stuffed it in the shielded PVC for a tight friction fit. I'm finishing up the wiring and enclosure assembly now.

Don

Got my kit of parts yesterday.  My youngest son was ecstatic since it came in a German language box with a cool clock on it. 

He was crushed when I opened it.  Now I'll have to come up with some sort of consolation prize for him.

I'm very happy.

Nonetheless, IF one could find shrink tubing just the right size to get the cores in, why not put the assembly together without any glue at the joints at all, slightly compress the whole stack and then shrink the tube assembly?  No glue, tightly held, and apparently the function of a rod built up from many pieces, as long as the ends are in close approximation, don't need any sort of fixation to conduct the magnetic lines through them, and glue is superfluous to function.

JB Weld might be stronger, but then again the problem is that cores are inherently fragile already, and to expect the last few millimeters of a compressed substance to hold tight is really asking a lot.  I'm still interested in the idea of using a dremel or such to make a little dimple or 5mm hole into the rod so that a load capable glue like epoxy can get more area of purchase to adhere to and distribute the load from the rod next to it through more of an area than just those smooth surfaces.

Darn, I should have ordered MORE of those rods when the order went in.




Title: Re: My home-made ferrite antennas
Post by: dfroula on August 18, 2013, 09:59:09 AM
There has been no degradation in performance with the re-glued rods. I do think that shrink-wrapping the glued rods before winding or the entire antenna assembly after winding. will provide excellent mechanical stability. Even if the glued joint were to fracture within the shrink tubing, I do not think performance would be affected at all, as the ends would still be held tightly together, as long as the shrink tubing extended past the ends of the assembly to provide pressure longitudinally.

I found 25 feet of 3/8 inch blue shrink wrap on Ebay for about $8.00 with free shipping. This is a great price. Lowes wanted $35.00 for 48 inches of the stuff!  Lots of colors are available at this price.  I'll use this stuff to protect and stabilize the assemblies when it arrives. I plan on making 3 sets of antennas from the 32 rods I ordered.

Egon warned me about unwanted self-resonance in the 10KHz to 100KHz area if I close-wound the wire directly on the ferrite. However, I looked at Richo's PDF file with frequency response plots of various ferrite antennas, including one very similar to mine (20CM, close wound to within 5mm of each end, directly on the ferrite). The response was perfectly flat across the 10KHz to 100KHz band. Self-resonance disturbances did not appear until much higher frequencies.

Best,

Don
Title: Re: My home-made ferrite antennas
Post by: DaleReid on August 18, 2013, 02:22:50 PM
Don,
As always, thanks go to you and others with the first rigs up and also the time to do a bit of futzing about.

I'm off to sniff for shrink tubing.  Glad you told us the size the look for that will work with these rods from Nebraska.
Dale
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 21, 2013, 04:45:04 PM
I received the shrink tubing for the ferrite antennas today. Following advice from the forums, I decided to encase the completed ferrite assemblies, re-glued with epoxy, in shrink wrap. I used 3/8 inch tubing which was just wide enough to slip the entire assembly inside easily. I then shrunk each end and the center portion, to insure that the ferrite segments were squeezed together by the wrap longitudinally. This ended up working really well. The final assembly is quite secure and break-resistant.

This is one of the epoxied re-glued cores, almost finished winding.
(http://projectmf.homelinux.com/station_pics/Ferrite_10.jpg)

Just a few mm to go. The epoxied and taped joint can be seen beneath the winding.
(http://projectmf.homelinux.com/station_pics/Ferrite_11.jpg)

The ferrite assembly being slide through the heat shrink
(http://projectmf.homelinux.com/station_pics/Ferrite_12.jpg)

...and shrunk with the heat gun, starting with each end first
(http://projectmf.homelinux.com/station_pics/Ferrite_13.jpg)

The wire lead end after shrinking.
(http://projectmf.homelinux.com/station_pics/Ferrite_14.jpg)

The opposite end after shrinking
(http://projectmf.homelinux.com/station_pics/Ferrite_15.jpg)

Before and after shrink wrapping
(http://projectmf.homelinux.com/station_pics/Ferrite_16.jpg)

The second antenna being prepared
(http://projectmf.homelinux.com/station_pics/Ferrite_17.jpg)

Two antennas completed
(http://projectmf.homelinux.com/station_pics/Ferrite_18.jpg)

Four antennas completed. I made a total of six.
(http://projectmf.homelinux.com/station_pics/Ferrite_19.jpg)

3/4 inch PVC conduit for housing the ferrites showing the aluminum tape shielding and slits
(http://projectmf.homelinux.com/station_pics/Ferrite_20.jpg)

Components of the ferrite antenna housing. The antenna assemblies are wrapped in thin foam and friction-fit in the tubes. The tubes are tapped into the "L" box, where the connections to the shielded cabling to the amp are made. The tubes are friction fit into the "L" with a thin coat of silicone grease to ease assembly/disassembly. The same was done with the end caps.
(http://projectmf.homelinux.com/station_pics/Ferrite_21.jpg)

The back and cover of the conduit "L" junction box.
(http://projectmf.homelinux.com/station_pics/Ferrite_22.jpg)
Title: Re: My home-made ferrite antennas
Post by: DanS on August 21, 2013, 06:06:11 PM
Very professional looking job. 2 questions with the metal shielding, do you ground the shields to the circuit ground and is it important or does it matter the direction that the slot in the shield points when mounted? Thanks.

Dan
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 21, 2013, 09:44:30 PM
Shrink-wrapped antenna ready to wrap in live-rubber foam sheet.
(http://projectmf.homelinux.com/station_pics/Ferrite_23.jpg)

Wrapped and taped in live rubber.
(http://projectmf.homelinux.com/station_pics/Ferrite_24.jpg)

Padded antenna inserted into 3/4 inch conduit.
(http://projectmf.homelinux.com/station_pics/Ferrite_25.jpg)

Wiring inside of "L" junction box.
(http://projectmf.homelinux.com/station_pics/Ferrite_26.jpg)

Finished antenna system with DB9 connectors for easy antenna switching between loops and ferrites.
(http://projectmf.homelinux.com/station_pics/Ferrite_27.jpg)

Side view
(http://projectmf.homelinux.com/station_pics/Ferrite_28.jpg)
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 21, 2013, 09:48:27 PM
Dan,

The shields are tied to one side of the ferrite winding (the return wire from the winding end). Both wires are connected to the grounded side of the amp input, which is in turn grounded through the shielded Ethernet cable to the controller board and its ground.

The orientation of the slot makes no difference at all.

Best,

Don

Very professional looking job. 2 questions with the metal shielding, do you ground the shields to the circuit ground and is it important or does it matter the direction that the slot in the shield points when mounted? Thanks.

Dan

Title: Re: My home-made ferrite antennas
Post by: DaleReid on August 21, 2013, 09:51:55 PM
A  L O T of work to get these photos for the rest of us to look at and see what things other minds have thought of with fabrication that would have taken more time to figure out on our own, or serve as a jumping off point to modify as we have to with available materials.

What was the search you used for the heat shrink?  I find several, but wonder if you remember the vendor you chose?

Finally, what's live rubber? 

Title: Re: My home-made ferrite antennas
Post by: dfroula on August 21, 2013, 10:09:01 PM
Here's the vendor I used. He had lots of other colors as well:

http://www.ebay.com/itm/111116696223?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

"Live rubber" is thin rubber foam sheeting that hobby shops sell to wrap model airplane fuel tanks in to prevent the fuel from foaming with engine vibration. Dubro makes and sells it in two-sheet packages. The stuff is hard to describe, except it is very spongy and resilient. It makes a great shock absorbing material.

http://www.amazon.com/Du-Bro-513-Protective-Foam-Rubber/dp/B0006NATXY/ref=sr_1_1?ie=UTF8&qid=1377139165&sr=8-1&keywords=Du-bro+rubber

Don
Title: Re: My home-made ferrite antennas
Post by: DaleReid on August 21, 2013, 10:33:26 PM
Thanks, I did grab a roll of it, knowing it was big enough to fit your antennas after wrapping, and shrank down enough to be snug.

I think I know the rubber you're speaking of, and saying it is used by RC'ers, I'll know where to look or a couple buddies who may have some from their building days.

It feels sort of funny if I remember correctly.

Thanks again. 
Title: Re: My home-made ferrite antennas
Post by: DaleReid on September 04, 2013, 04:16:36 PM
Don,
After two weeks of non-lightning hell with family, work and the holiday, I'm getting nearly ready to begin.  Finally.

I have the ferrites, and am sure I have some 26 wire, found the 24 but it is a bit big.

A question on winding the cores....

Did you start at the right end, and wind over the top (spinning the top of the core away from you) or underneath (spinning the core down and 'towards' you?).

As long as you do both the same, it shouldn't make any difference, correct?

Which of the ends did you designate the 'ground' wire, or again, if you just make sure the lead from the same end of each is connected together, that is OK?  I see you loosely spiraled the one wire to the other end making a couple wraps going from the right end to the left end in the photos.  I assume that this is just to make it secure.  With the taping and final shrink wrapping, I wonder if it is OK to just go straight to the opposite end to pair up with the free end there, or is the loose wrap necessary?

I would think that there isn't much concern about the antennas being circularly polarized by phasing them differently; that is, if one took Core A and had the free ends 1a and 2a and Core B with free ends 1b and 2b, then just choose one, say the 2 wire, to be ground and do the two wire from each core to designate as ground?  Sorry if this isn't too clear.

Thanks for any further info.

Anything you've learned since the construction?

Dale
Title: Re: My home-made ferrite antennas
Post by: dfroula on September 04, 2013, 05:41:27 PM
Well, I wound the cores by holding the ferrite rod vertically with the spool of wire to my right. I crossed the wire from right to left over the top of the ferrite and commenced winding by rotating the rod clockwise (as viewed from the top of the vertically oriented rod).

I wound the length of the rod in this fashion until reaching about 5mm from the bottom of the rod. I taped the winding to stabilize it at the bottom end and continued winding in the same direction back to the top or starting end of the rod, in a loose spiral. This gives a "right handed" or clockwise winding, like the thread on a screw.

Following the construction of the Blitzortung-supplied ferrites, the end of the loose spiral becomes the ground connection of the antenna, and the starting end of the winding is connected to the ungrounded terminal of the amp. I don't think this is critical, though. There is supposedly some shielding benefit from doing this, but I don't think it is much. It is preferable to connect both antennas the same way to make the phasing of the antennas the same. Connecting as above is a convenient convention.

Winding and connecting as above should preserve the relative phasing of the antennas. In other words, if the two ferrite antennas were wound and connected as above and placed parallel to one another, the two traces on the signal scope would show impulses of the same amplitude and polarity in response to a lightning strike (assuming equal gain).

If one antenna were wound in the opposite direction or the connections reversed on one, the amplitudes would be the same, but the polarities would be opposite. I don't think this would really matter for the Blitzortung system, as the system triggers equally on positive or negative impulses.

Antennas for the "Lightning Radar" system DO need to be concerned about the phasing, as they use the polarity and relative amplitude of the two antennas to determine the bearing of the signal. TOA systems don't care.

I hope this helps!

Don
Title: Re: My home-made ferrite antennas
Post by: dfroula on September 04, 2013, 05:47:22 PM
Well, I wound the cores by holding the ferrite rod vertically with the spool of wire to my right. I crossed the wire from right to left over the top of the ferrite and commenced winding by rotating the rod clockwise (as viewed from the top of the vertically oriented rod). I think this is the same winding direction as you described in your first example.

I wound the length of the rod in this fashion until reaching about 5mm from the bottom of the rod. I taped the winding to stabilize it at the bottom end and continued winding in the same direction back to the top or starting end of the rod, in a loose spiral. This gives a "right handed" or clockwise winding, like the thread on a screw.

Following the construction of the Blitzortung-supplied ferrites, the end of the loose spiral becomes the ground connection of the antenna, and the starting end of the winding is connected to the ungrounded terminal of the amp. I don't think this is critical, though. There is supposedly some shielding benefit from doing this, but I don't think it is much. It is preferable to connect both antennas the same way to make the phasing of the antennas the same. Connecting as above is a convenient convention.

Winding and connecting as above should preserve the relative phasing of the antennas. In other words, if the two ferrite antennas were wound and connected as above and placed parallel to one another, the two traces on the signal scope would show impulses of the same amplitude and polarity in response to a lightning strike (assuming equal gain).

If one antenna were wound in the opposite direction or the connections reversed on one, the amplitudes would be the same, but the polarities would be opposite. I don't think this would really matter for the Blitzortung system, as the system triggers equally on positive or negative impulses.

Antennas for the "Lightning Radar" system DO need to be concerned about the phasing, as they use the polarity and relative amplitude of the two antennas to determine the bearing of the signal. TOA systems don't care.

I hope this helps!

Don
Title: Re: My home-made ferrite antennas
Post by: DaleReid on September 04, 2013, 07:22:03 PM

Thanks,

I thought as much but since you have them up and running thought I would just ask.  Once the wire is off the spool, it is hard to take off and re-wind.

Consistency is the key, I think.  And unless one is phasing something like a helical antenna for proper circular polarization, there isn't much to worry about, until the LR issue came up.  But then again doing it as you suggest takes care of the potential problem.

Dale
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on September 24, 2013, 07:07:59 PM
Well, Don et.al.
 =D> I just rolled two of these and slapped 'em on the amp about 2 1/2 hrs ago.
I am blown away.
Operating under the theory that, with Scotch and a few other things, more is better,  I used 6 rods for a 300mm rod.

Didn't bother to glue them together, figuring the heat shrink would do the job just as well...  So I stacked 'em in some 3/8" clear polyvinyl heat shrink, and squeezed 'em together.
So the 'rod' sagged a bit. with no coil and no second shrink tube. So what... no biggie, we're just starting on the build

Rolled it, +/- 725 turns of 26ga enamel, total coil length of 290mm.
Heat shrunk it again with 1/2" tubing, to fix the sag and wiggle, left it unshielded, and marched out (ok, ran out  :-P ) to the garage in anticipation.

Slapped the first one in B channel, oriented it N-S to match A (the original 120mm) cut gain in half on the 300 to get out of interference  :grin:
 set the A amp (120mm) to match, and compared signals.
The gain is approx 3 times that of the 120mm ferrite, and about half the noise floor. Much quieter than the flat panels, also. The signals seem to have better resolution.
 \:D/  \:D/  =D>

Repeated the process with #2.

Now, the acid test at sunset, when we see what it takes to overcome the nearby Sodium street lights.
I may eschew shields... we'll see.

Thanks, Don! Great antennas, simple to build, and real jewels so far!

Mike
Well, there comes the first sodium, as I type this. At three times the previous level interference level  :-| ... Now to 'speriment with shielding....
Title: Re: My home-made ferrite antennas
Post by: dfroula on September 25, 2013, 10:22:31 AM
Great! The extra length helped, I'm sure. I still have my flat panels mounted, but have been running the ferrites for a few months and will likely stick to them. I built up two more complete ferrite antennas in enclosures....not sure why, but I had the components, so why not?  :grin:

I found that the shielded tubes helped tremendously with power line hum. I have no identifiable noise sources when listening to the amp output, other than very low level 60 HZ stuff and slight processor noise from the controller (which I know is too close to the antennas, but doesn't affect performance at all).

Don
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on September 30, 2013, 04:09:01 PM
Here are my 300mm versions of Don's antenna, "cardboard-breadboarded" under testing...
No glue used, just shrink over the cores, and another layer of shrink over the winding.
These are quite rigid as they stand, and seem to work better unshielded.

(http://www.ourspecialnet.com/Weather/TwinHollies/i-TmgK945/0/L/300mm_testing-L.jpg) (http://www.ourspecialnet.com/Weather/TwinHollies/30312224_5r5QZ6#!i=2801318213&k=TmgK945&lb=1&s=A)
Happy Winding!
Mike
Title: Re: My home-made ferrite antennas
Post by: Jumpin Joe on September 30, 2013, 04:30:59 PM
Nice Mike... I found my 120's from Egon work better with shielding.

Getting ready to make the "12" Ball" antenna that "scarecrow93" (Lance), made. His stat's seem to stay pretty consistent and strong.

Received all the stuff to build it today. I hope to have it done later this week. Have to finish some of my honey-dew's first.

Joe
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on September 30, 2013, 05:08:31 PM
My 120's were better with shielding, also... these do fine without it,... must be the magic touch.
All that bothers me are some street lights, and something new that's developed this past week, around 55Khz, that drives me a bit nuts... 55Khz is, among other things, some infrared mod freqs, and I suspect somebody's got something new in their home nearby that's leaking heavily, because of the timing of the events... ah well.

Mike
Title: Re: My home-made ferrite antennas
Post by: Jumpin Joe on September 30, 2013, 05:50:00 PM
Oh... I thought it was on of the Cincy radio stations ... lol
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on September 30, 2013, 06:06:55 PM
Oh... I thought it was on of the Cincy radio stations ... lol
Because of the typical timing, and the spouse's schedule, I've accused her of being 'too hot to handle'... as it only seemed to appear when she was home and awake.

(...and she actually thought it a compliment! Lucky me!)  8-)

Mike
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on February 01, 2014, 06:13:55 PM
Let's see if we can bump this topic, since we may have new builders looking for help on Don's ferrites...
Title: Re: My home-made ferrite antennas
Post by: W3DRM on March 29, 2014, 12:59:50 PM
Okay, I'll try it. Have just ordered some shrink-wrap tubing. Have everything else so once the tubing come in I'll be ready to build my first ferrite. Have had the ferrites for quite a while now (hope I can still find 'em...). More later.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 29, 2014, 02:27:04 PM
Mr. Sailor:

How appropriate for a refresh on this topic.

I was just in communication with Jim in Wisconsin and am getting the table cleared of all the tax forms and other stuff of Winter's detritus so I can get the board up and running.

With your encouragement, perhaps I'll work on the rods first, and get a feeling of starting without soldering teensy weensy surface mount thingies at the beginning.

Is your opinion that these rods still work fine without a shield, or is that really going to be necessary?  I read that the ones supplied from the project assembler NEED shielding.  You said not so much for yours.  Just because they are longer?  You have a lucky location?  Isn't the E field shielding a requirement for the detector to work?

Nonetheless, I'm pleased IF they do work without shields since it is just one less putzy thing to do, and with that type of thing more often than not my work is a bit glue and rubber bands to hold everything just right without shorting the wrap around together.

Speaking of glue and rubber bands, you mentioned that your ferrites work fine without gluing them into a solid rod, but had a wee bit o' the sag in the assembly.  Would you think a tiny dab of hot glue at 12, 3, 6 and 9 oclock around the butt joint of each rod as it is assembled into a long one, would be of help or is the second heat shrink taking care of the solidity of the unit?  I'd not put the glue between the rods, just around the intersection on the outside to hold them during winding.

Dale
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on March 29, 2014, 03:21:26 PM
Hey, Dale..
Is your opinion that these rods still work fine without a shield, or is that really going to be necessary?  I read that the ones supplied from the project assembler NEED shielding.  You said not so much for yours.  Just because they are longer?  You have a lucky location?  Isn't the E field shielding a requirement for the detector to work?
Yes, they'll work. If I moved mine to a different location they might need shielding, but I've run them with and without, and though there is some slight decrease in my noise level, there's no appreciable effect in overall performance, at my location. Keep in mind that it appears I have high H field interference, but very little consistent E interference that I can determine, and my antennas are placed in the only 'sweet' spot I've been able to locate in my residence.

A shield can always be added later... if you have E interference this also gives you a chance to help track it down, and remedy it if necessary prior to shielding.
Quote

Nonetheless, I'm pleased IF they do work without shields since it is just one less putzy thing to do, and with that type of thing more often than not my work is a bit glue and rubber bands to hold everything just right without shorting the wrap around together.
You can use self adhesive aluminum tape from HVAC dept at Lowes. Just on a whim, last shields used this:
http://www.amazon.com/gp/product/B00ANTRRRM/ref=oh_details_o08_s01_i00?ie=UTF8&psc=1
but I did purchase it when it was priced much lower, for whatever reason....
I think it was easier to handle, and a tad faster than using the wider aluminum foil... either way it doesn't take long. Just wrap a thin piece of printer paper around the antenna (1 layer) and a couple pieces of scotch tape to hold the paper tube... then stick the shielding copper or aluminum tape to the paper... and if you don't appreciate the shielding it's easily removed.  ;)
Quote

Speaking of glue and rubber bands, you mentioned that your ferrites work fine without gluing them into a solid rod, but had a wee bit o' the sag in the assembly.  Would you think a tiny dab of hot glue at 12, 3, 6 and 9 oclock around the butt joint of each rod as it is assembled into a long one, would be of help or is the second heat shrink taking care of the solidity of the unit?  I'd not put the glue between the rods, just around the intersection on the outside to hold them during winding.
The little sag in the first layer of shrink wrap mattered not. You're going to wind the coil over it, and use a second layer over the coil. By the time that's done they're quite rigid, no floppiness even with my 300mm length.
I wouldn't use glue of any type at all since the following method is almost foolproof:
I used a tilted shoebox lid, laid the core sections in the 'v' between the top and side, slid the wrap over the cores (should extend an inch or so beyond the core ends) and began shrinking from each end alternately --- ending in the center--- Shrinking each end first, and alternating left and right ending in the center draws the rods together and locks them as the wrap shrinks. you don't need rubber bands, glue, etc... The cores then assume the properties of one long core through magic.

Mike
Title: Re: My home-made ferrite antennas
Post by: dfroula on March 29, 2014, 04:43:42 PM
As I just wound Dave Robbin's antenna's, here's a comparison picture. The shorties are 5 rods, glued, wound directly onto the ferrite with a single layer of shrink tubing over the entire thing.

The longer ones used Mike's technique, except I did glue the rods with epoxy in a jig to add some extra stability during winding. I was able to use the same diameter shrink tubing (3/8") for both layers. That diameter easily accommodated the wound cores for the final wrap.

I did find that the wire was easier to wind on the core with the shrink-wrap than on the bare ferrite, due to the friction of the material.

There is a noticeable gain boost with the extra length.

As for shielding, Dave's units seem fine without it. I found that it helped mine some with the noise floor and some noise sources. It didn't seem to affect the gain at all. The shields will make any electrical noise worse if not grounded, as I (and Jim in Mauston) discovered.

If you use shields, ground 'em!  #-o

Don F.
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 29, 2014, 05:37:23 PM
I'll take the hot glue gun back out to the shed (which I can now access with the snow finally melting and a whole 44 degrees today) and proceed with lining up some ferrittes and shrinking.

Thanks for the tip on doing ends first and alternating back in towards middle.  Luckily I ordered a spool of the heat shrink when this thread first started and was pleased with it, both quality appearance and price.

I have some extra rods, and will indeed stack another one or two on.  Greg, how many did you use for the longer assembly?

Will this alter the electrical appearance to the preamplifier?  More wraps, more length of wire, more resistance, change in inductance, etc. 

You obviously have the test setup and the previous experience to do this, and from your comments you did not hesitate a bit.  I think there was some lengthy discussion earlier, but if it works, if there is more gain, better to do it now.  I have some 28 and 24 wire, no 26 to wind.  Can I get a better antenna by taking the time and extra effort to wind the smaller gauge and therefore get more turns on the same length of rod?  Or again, having something is better than trying to tweak?

I remember spending hours with a Bird meter and peaking the 2 meter antenna on one of my first mobile installs, very proud of myself for a minimal SWR.  Then a guy who is chief engineer for a radio company pulls up with his truck and, I kid you not, a piece of insulated wire just soldered to a button that was in the top of the old Motorola mount he had and it worked as well as mine...  I guess if I were listening for earth moon earth signals I'd be more worried. 

Thanks again.  Getting the stuff out now.  Dale.

Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 29, 2014, 05:42:20 PM
Even though the Scotch is still in the bottle, I went back to re-read and found the answer to number of cores.  5 for the original wrap and one more, total 6, for the longer one.  Thanks.
Dale
Just being a nervous nellie.

Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on March 29, 2014, 07:12:20 PM
I'll take the hot glue gun back out to the shed (which I can now access with the snow finally melting and a whole 44 degrees today) and proceed with lining up some ferrittes and shrinking.
Good!
Quote
Thanks for the tip on doing ends first and alternating back in towards middle.  Luckily I ordered a spool of the heat shrink when this thread first started and was pleased with it, both quality appearance and price.


I have some extra rods, and will indeed stack another one or two on.  Greg, how many did you use for the longer assembly?

Will this alter the electrical appearance to the preamplifier?  More wraps, more length of wire, more resistance, change in inductance, etc. 
no problem
Quote
You obviously have the test setup and the previous experience to do this, and from your comments you did not hesitate a bit.  I think there was some lengthy discussion earlier, but if it works, if there is more gain, better to do it now.  I have some 28 and 24 wire, no 26 to wind.  Can I get a better antenna by taking the time and extra effort to wind the smaller gauge and therefore get more turns on the same length of rod?  Or again, having something is better than trying to tweak?
Really recommend good quality enameled 26 gauge.... here's what I used:
http://www.amazon.com/gp/product/B0082CUNVE/ref=oh_details_o04_s00_i00?ie=UTF8&psc=1

Relax... this isn't that complex...

Mike
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 29, 2014, 09:27:10 PM
I just heat shrunk six cores together.

The nice tubing that was recommended is so tight that by the time I got to the middle, there was trapped hot air.  I fussed until I thought about it a bit and made a tiny cut across the middle of the bubble and it came down nicely.

Now, where's that wire....

Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 29, 2014, 10:52:32 PM
Antennae are done!

I got brave and decided to try a wrap.

I used #28 wire since it was the only magnet wire I had other than 24 and I figured that was too course and would not allow enough turns.  I anchored the free end with a wrap of tape, leaving about 2' sticking out and put the spool of wire on an empty blank CD spindle, which worked great for keeping the wire spool in place, and provided just the right amount of un-wind tension to keep the wire coming.  It didn't take long to notice two things.  First, it was pretty easy to get the right amount of pressure between my thumb and forefinger to get the wrap tight, and the angle that the wire coming off the spool was easy to adjust and keep as it made a tight wrap with no gaps.  Secondly I found that the free 2' end of wire was almost as snarly as most fishing lines when unrestrained.  I finally settled on trying to gently straighten out the rat's nest that had formed, and to keep the wire extended directly along the same axis as the cores, which were turned.  I'm sure some torsion of the wire occurred, but despite flopping around a bit and keeping the end from catching on stray stuff on the work bench, worked pretty well.

Needless to say, the second core went much faster and was neater and less twisting on the free end.  After taping the final end wrap, I did a gentle spiral up (thanks for the pictures!) and then secured it at the top, leaving another two feet to use for connections.  I did mark the start end and the final end for phasing later.

I found the process fun and strangely calming, similar to when Nurse Chambers helped us with basket weaving at the Happy Thoughts Farm and Sanitarium, but this time no doors were locked and I didn't see any nice young men in white coats.

I will heat shrink the second coat over the assembly tomorrow, and get the necessary plastic parts to hold the diagonal angles as needed and secure the delicate wires.


Now, however, the tough part begins with sorting the numerous resisters, capacitors and start on the board assembly, which probably won't go as quickly and I may see some white jackets called in.

Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 29, 2014, 11:03:36 PM
Don,
While studying your pictures of the PVC pipe 90 degree holder with the L box you used, there is a red wire with periodic blue stripes on it.  I assume, but need to ask, if this the ground wire for the tape shield you have made, since the magnet wires seem to be run into the box independently and it isn't just one of them spliced to the heavier duty wire for a more robust wire to handle?

Dale
Title: Re: My home-made ferrite antennas
Post by: dfroula on March 30, 2014, 05:53:21 AM
Yes, that's the ground wire. I have enough 24 AWG telephone patch panel interconnect cable with the colored-band coding for several lifetimes, so I used that. The colored wire connects to the aluminum foil shields.

I used aluminum foil tape designed for sealing sheet-metal air ducting for the shields as it was cheap and available. One width of the widest tape I could find was not sufficient to wrap completely around the PVC tubing that I used as enclosures for the ferrite antennas. I had to overlap two strips, leaving the narrow gap in the shield.

Doing this presents two problems.

The first is that the two layers of tape have no electrical conductivity to one another because of the adhesive.

The second is that (as most of us are aware), one simply cannot solder copper to an aluminum surface, at least not without special flux and techniques.

I solved both issues by drilling a small hole through one of the foil layers at one end of the tube. I strip a few inches of insulation from the wire and pass the bare end through the hole from the inside of the tube. I then bend the bare wire into a tight "S" shape and bend it to overlap the two layers of foil. I secure the "S" with a short length of foil tape directly across the wire "S", covering the hole as well. I burnish this strip down tightly with a small dental tool to give better contact.

I got the idea when constructing a few of Gerry's flat panel antennas from aluminum-clad foam board. It has worked fine in both applications.

I solder the shield ground wire and the ground side of the antenna (the loosely wound wire from the end of the winding) together with the shield braid and black wire from the shielded pair microphone cabling I use for the interconnect between the amp and antenna. I solder the other end of the antenna winding to the red wire of the cable.

It is really important not to reverse the ground and hot sides of the antenna connections to the amp. One side of each amp connection is at ground potential. The shielded braid of the cable and grounded end of the antenna wire MUST connect to the grounded side of the amp input. You won't blow the amp if you reverse them, but if you do, the shield becomes part of your antenna and you will find all sorts of strange noise pickup.

Don
Title: Re: My home-made ferrite antennas
Post by: Silversword on March 30, 2014, 03:11:02 PM
Hi All,

Thanks for all the info in wiring the ferrite antenna wrapping.  I am still waiting for the shrink wrap that should be here this coming week.  Got the ferrite cores yesterday.  Also got the electrical conduit and the "L" coupling and end caps. Almost ready to go.

Also got the Bud cases, shielded CAT cable a 3' for testing and a 25' for placing the amplifier/antenna somewhere outside.

I still have to do the boards but got the parts separated.  I am old school in resistor reading (4 band) and not versed in the 5 band configuration.  Here is a good link for using the color scheme http://www.hobby-hour.com/electronics/resistor_color_code.php (http://www.hobby-hour.com/electronics/resistor_color_code.php). or you can just the VOM to find out what they are. Some colors on the resistors are hard to see what they are.

Anyway, looks like I am on my way to get this project done between keeping up with mowing my yard because of the rains we have been getting the last few weeks. We are almost doubled for this years average at this time of year.  Some flooding in the area.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 30, 2014, 08:34:48 PM
Don,

In your lengthy post with the great pictures on winding and then shrink wrapping the rods, plus inserting them into the PVC with the L box for a mount, you seemed to run the wires inside and connect them there, but not really tie them down.  Not that they'll need a lot, but my first impulse was to perhaps glue a terminal strip to the back of the L box, and then use that to join the delicate wires from the antenna windings to the outgoing, more substantial, shielded cables.  Was there a reason for doing it as you did vs. putting a six terminal strip back there, other than expense?  I assume once connected all is fine and a couple wraps of wire around the shielded stuff and a hit of shrink wrap to insure nothing moves or touches is a lot cheaper, but are you aware of any problem with trying a strip?

Just curious.

Dale
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 30, 2014, 08:45:34 PM
Don, I forgot to ask if the connectors (look like DB9s) in the shielded wire from the antenna to the preamp are a nice touch, but again if one isn't anticipating a lot of experimentation with trying ferrites vs. balls vs patch vs styrofoam board, is there a reason to put the connectors in there?

You have a lot of experience and were on the bleeding edge, so you seem to attract the most attention for questions on this project.  Let us know if you want us to back off...

Dale
Title: Re: My home-made ferrite antennas
Post by: dfroula on March 31, 2014, 04:39:21 AM
Dale,

I sure don't back off on the questions when I'm trying to figure something out.  :eek: Please ask as many as you like.

Well, funny you should mention it.....the db9 connectors did not work out at all. I have a huge box of surplus Amphenol DB9 shells and male/female solderable connectors. The problem was the connector body is loose within the aluminized plastic shell. Any movement of the connector in the shell caused severe noise in the receiver. Also, the cable lengths in the picture are far too long.

Now, I just use a terminal strip on the shortened cables to the antenna. I have another very short set of cables perymanently connected to the amp in the enclosure, going to the other side of the terminal strip. It works fine.

Don
Title: Re: My home-made ferrite antennas
Post by: W3DRM on March 31, 2014, 11:41:28 AM
While I wait for my shrink-tubing to arrive later this week, I just realized that I don't have a heat-shrink gun. Any suggested brand better than another? I do have a Harbor Freight store within 20 miles and may just go there to pick up one of their cheapies. They have several models on sale at the moment.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 31, 2014, 12:07:24 PM
I just now am cooling off my Harbor Freight gun after heat shrinking with it.
I used to use my wife's hair dryer with minimal and mixed success.

I found this orange thing at Harbor Freight and was a bit skeptical, especially for the price.  But it has two speeds, I have NEVER burned a piece of tubing with it, unlike the efforts with matches/torches/soldering iron/ lighters/etc.

I am sold on this low cost gun.  I've made many more heat shrinks than I would have, just because this takes the unknown out of shrinking and love the look (no solder globs on the tubing) and consistent results.

Go for a nice Monday drive, use your 20% off coupon you can find on their site if you don't already have a coupon for that specific gun.

I have to say, the source for the shrink wrap that I think Don pointed us to seems to be top notch.  I again thank all those who have tread the path before us for the tips they've given.

Dale
Title: Re: My home-made ferrite antennas
Post by: W3DRM on March 31, 2014, 03:14:19 PM
Thanks Dale. I'll try the HFT gun and see what happens. Tubing due in on Friday so it gives me time to get the tool beforehand. I've also had less than satisfactory results with my wife's hair-dryer as well as the other methods you described. I do have a 20% off coupon so will use that too.
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on March 31, 2014, 04:23:07 PM
Gee, wish we'd thought to mention WHD for heat shrink... would have suggested it might be ineffective...  #-o

Anyway, you ever thought about how many neat things you can do with a HAG and various types of plastic and shrink wraps??  :idea:  I mean besides burning the wings off pesky flies?
Title: Re: My home-made ferrite antennas
Post by: W3DRM on March 31, 2014, 04:51:26 PM
Gee, wish we'd thought to mention WHD for heat shrink... would have suggested it might be ineffective...  #-o

Anyway, you ever thought about how many neat things you can do with a HAG and various types of plastic and shrink wraps??  :idea:  I mean besides burning the wings off pesky flies?

Okay, it's probably clear to everyone else but me but, what does WHD and HAG refer to? I can't seem to come up with anything they might stand for except for "World Health Day" for WHD which I am certain isn't the correct answer...
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on March 31, 2014, 05:08:36 PM
 
Gee, wish we'd thought to mention WHD for heat shrink... would have suggested it might be ineffective...  #-o

Anyway, you ever thought about how many neat things you can do with a HAG and various types of plastic and shrink wraps??  :idea:  I mean besides burning the wings off pesky flies?

Okay, it's probably clear to everyone else but me but, what does WHD and HAG refer to? I can't seem to come up with anything they might stand for except for "World Health Day" for WHD which I am certain isn't the correct answer...
:lol:  :lol:  :lol:
I simply couldn't resist seeing who'd bite...
Wife's Hair Dryer and Hot Air Gun...  :twisted:

It's part of my illness...
Mike
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 31, 2014, 05:34:39 PM
Having choked on PTZ in another thread (Pan, Tilt, Zoom) for a webcam, I was licking my wounds and didn't bite.

Nice bait, though.

Title: Re: My home-made ferrite antennas
Post by: W3DRM on March 31, 2014, 05:51:57 PM
 :oops: Okay, ya got me!  =D> However, if one doesn't ask questions, one will never learn...  ](*,)

So, for the record, the WHD doesn't work so good as a HAG for anything but it's originally intended use but, I bet it would warm up those cold sheets on a cold winters' night...  \:D/
Title: Re: My home-made ferrite antennas
Post by: DaleReid on March 31, 2014, 08:04:11 PM
OT== speaking of wintery nights, we are struggling to melt snow, but warm winds and 50s today helped a lot.

Mud knee deep, neighbors with livestock have them all muddy.  My livestock is a German Shepard Dog who is inside some of the time and we are going through dog towels trying to keep the mud to a minimum.

And to top things off, the rest of the week has an even chance each day of snow, with Friday expected to have some 4 to 9" across MN and WI

When will it end?

Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on March 31, 2014, 09:27:47 PM


When will it end?


I'm calling it Done.  Put out the CoCoRaHS ETogage today, and reinstalled inner cylinder in the rain gauge. x'd fingers.
Title: Re: My home-made ferrite antennas
Post by: W3DRM on March 31, 2014, 09:47:46 PM
OT == We're under a winter weather watch tonight! Supposed to get down to around 28F tonight with blowing snow. The SIERRA ridges are looking at 24 inches overnight. Nothing like a late snow storm. Unfortunately, it will only bring the snowpack numbers up to around 40% of annual averages. Still way low and will likely make for water restrictions being enforced this summer.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on April 04, 2014, 09:27:09 AM
With 4-6" of wet heavy snow last night and this morning, with more possible, I'm finishing up my antennas.

I have wondered about the live rubber shock protection and think that I might just take some square cotton cosmetic make up pads that are about 2" square and sort of 1/4" thick and roll a couple around the middle of the rod, then after it is in place slide a cylinder of the cotton up over each end, watching the delicate wires.  The whole thing will be pretty sealed and will never get wet so I don't see that the cotton will saturate, but yet allow easy removal if ever needed in the future.

I measured the resistance of my winding with a sort of accurate dvm, and get about 5.4 ohms.  Is this the ballpark?

I have downloaded the latest RED documentation from Blitz, and looked at the nice pictures.  Most of the installs for ferrite antennas seem to NOT use the shielded wire to connect to the preamp, they just come out and solder the winding wire to a thicker wire or pin to make sure it gets good connection to the screw downs on the preamp board.

If one came up with something like a nice bread (literally!) board of plastic to mount the ferrite assembly to, ran the magnet wire out through the L box and directly over to a preamp box mounted near the junction of the two arms, would that have any disadvantage to doing what Don has shown with the shielded wire?  I assume for the time being that I'll be so ecstatic when my system is up and running that I'd not twiddle with antenna swaps and other tweakings at least for this lightning season, so being able to easily swap antennas and tweak wouldn't be a high priority right away.

Finally, I am loath to cut off any excess wire from the rods, since I have about a foot and a half to allow for errors, unexpected breakage, etc.  That would lead to a rat's nest of sorts, but to keep the safety net of a few extra inches, could one just make a short loose coil maybe about an inch in diameter and leave that in the protected area of the L box, or would having those coils (four total, two for each of the rods) interact or act as an undesirable influence on the antennas themselves?

Thanks. Dale (off to start the of Cub Cadet and do a little snow throwing for one last time.)
Title: Re: My home-made ferrite antennas
Post by: dfroula on April 04, 2014, 10:00:14 AM
The cotton idea should be fine. I used the "live rubber" Dubro sheets because I had some from building up a few RC planes. I think it's a good idea to wrap the shock-absorbing material around the entire length to avoid uneven pressures if the antenna is dropped or banged.

Likewise on the shielded microphone cable. I've had a spool sitting around for 15 years or so, so decided to use it.The direct wiring from the antenna magnet wire should be fine, if you are careful to scrape the enamel off the entire circumference of the wire ends. The 26 AWG makes good contact with the amp screw-down terminals without needing to solder on a thicker wire.

The resistance sounds about right.

At these frequencies, a few turns of magnet wire in the junction box should be fine. I've experienced no cross-coupling or other ill effects just stuffing the excess wire into the box.

Don
Title: Re: My home-made ferrite antennas
Post by: DaleReid on April 04, 2014, 11:18:05 AM
Don,
thanks for the reassurance and clarifications.  Your really pioneering work and experience means a lot to those of us nervous nellies getting started.

Two other things came to mind. 

The document from Blitz indicated that (while they showed several rods they'd wound up) making your own was frowned upon and described as difficult.  Difficult is soldering the GPS module on and the winding of the cores was dumb easy.  Could even be done after some Cutty Sark was on board if needed (none needed here).

Second thing is how does one 'easily' remove the enamel off the wire?  For thicker magnet I have gently scraped with a blade, hoping to get only the enamel and not any copper.  The thinner is tougher to do.   Hams who wind their own inductors for old stuff say they can gently heat it off.  Others use fine sandpaper and grab the wire and pull the paper towards the end. Others have suggested dissolving it with acetone (in the correct non-flame, openly ventilated area).

With my #28 wire I want to be careful yet provide a good contact.

The proof is in the doing and what works, obviously.  Always looking for tricks.

Dale
Title: Re: My home-made ferrite antennas
Post by: miraculon on April 04, 2014, 12:31:15 PM
Don,
thanks for the reassurance and clarifications.  Your really pioneering work and experience means a lot to those of us nervous nellies getting started.

Two other things came to mind. 

The document from Blitz indicated that (while they showed several rods they'd wound up) making your own was frowned upon and described as difficult.  Difficult is soldering the GPS module on and the winding of the cores was dumb easy.  Could even be done after some Cutty Sark was on board if needed (none needed here).

Second thing is how does one 'easily' remove the enamel off the wire?  For thicker magnet I have gently scraped with a blade, hoping to get only the enamel and not any copper.  The thinner is tougher to do.   Hams who wind their own inductors for old stuff say they can gently heat it off.  Others use fine sandpaper and grab the wire and pull the paper towards the end. Others have suggested dissolving it with acetone (in the correct non-flame, openly ventilated area).

With my #28 wire I want to be careful yet provide a good contact.

The proof is in the doing and what works, obviously.  Always looking for tricks.

Dale

There is solder-stripping magnet wire. I have used it in the past. I see some available on eBay and other sources.

e.g.: http://www.ebay.com/itm/Magnet-Wire-40-AWG-Gauge-Enameled-Copper-2oz-155C-3990ft-Magnetic-Coil-Winding-/261087238074 (http://www.ebay.com/itm/Magnet-Wire-40-AWG-Gauge-Enameled-Copper-2oz-155C-3990ft-Magnetic-Coil-Winding-/261087238074)

Greg
Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 04, 2014, 03:30:03 PM
The above links also leads you to a YouTube video showing how to strip the insulation off the magnet wire:

Personally, I either use my diagonal cutters or a piece of fine sandpaper. Either method is quick and easy. I always tin the wires after stripping it and prior to making the solder connections as it makes soldering a bit easier.
Title: Re: My home-made ferrite antennas
Post by: Silversword on April 15, 2014, 05:55:06 PM
Hi,

I started to construct (wind) my ferrite antennas while waiting for a part to come from Egon.

I had an issue with the heat shrink using the method previously described. Heated the ends first that worked toward the middle from both ends.  When I got to the middle somehow the heat shrink got between the center core and had a gap.  I did not glue each segment. Got frustrated with that method.  So I redid it by putting one core at a time and shrank one end but not going to the other end of the core.  Inserted the next core and used a small dowel that I had to push that core against the first one and proceeded to shrink over the butted area.  Went down the line using this technique for all six cores and got both of the 300 mm rods completed this way. No gluing or taping involved.

Next it is time to wrap it and another layer of shrink wrap session and put them in the PVC enclosure.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii


Title: Re: My home-made ferrite antennas
Post by: corwyyn on April 16, 2014, 08:02:55 AM
Stan, I had a similar problem when I tried to shrink-wrap some loose cores for one of my antennas, luckily I had plenty of tubing left so I removed the bungled tubing and tried again only this time I made sure to press in on the end cores so that I knew they were all seated against each other.  After that it went together nice and snug with no gaps.  The other antenna I glued the cores together and put them in the shrink tube, that one was easy to get finished.  Now I've got one finished with a bunch of turns of 24ga wire and I plan on getting the next one done this coming weekend after my hands recover :D  Hopefully I'll also get some time to start on building the boards.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on April 16, 2014, 08:52:38 AM
I was tempted to shrink wrap from one end only, but then thought about loosing out on the compressive effect that the tubing has as it slightly shrinks end to end, of which there is little.

I ran into a trapped air bubble in the middle.  The darn stuff was so tight against the ends that as I approached the middle, there wasn't enough leakage around the two end cores to let the air out.  A slight slice in the bubble in the middle and it came together very well.  The 2 mm or so puncture 'healed' with the shrinking much to my relief.

I just finished the amplifier board yesterday.  Very enjoyable AFTER I got a soldering tip and iron that allowed me to make good contact.  Even in this 100,000 population town, the only irons I could find were are Radio Shack and they looked like they were sized to do plumbing.

The controller board is slated to start today if I can get home from work early enough. I'm still worried about the GPS chip, but the rest of it should be a piece of cake with the experience I learned from the first board.

Sorry to dribble on about the lessons learned, but really bright light helps, and I appropriated my wife's stitchery ring light with magnifying lens in the middle to help out, even with illumination while a high power set of reading glasses (I did find some 3.5 diopter) and a head mounted stereo pair of lenses gave me more confidence.

The surface mount chips went surprisingly well.  I understand that for someone doing a lot of recent soldering, it would be no problem.  But, because of the access to the board without other components nearby necessitating the SMD installation right away, it means you are learning your soldering skills of years past on the most touchy part, with no recent experience or confidence.  I almost, almost, look forward to doing the next System Blue evolution board, or whatever it will be called.  Sort of fun.

The hardest thing to do, the micro USB connector.  The part in my kit had solder leads barely to the surface of the back side of the board, and to get heat to those pins and not just form a solder blob in the micro hole was a bit tough.  I wish the would have been a wee bit longer and stuck up through the board to have a physical contact with my iron to heat it.

But, to my delight, surprise and relief, at 10:30 last night after numerous rechecks under the bright light and magnification, I plugged it in and lights blinked, the reset button worked and I could vary the number of yellow LEDs lit by moving the potentiometer.

Oh, a plug for the step by step instructions that have been provided by another member, and I sincerely apologize for not having those notes with me as I type this; I cannot say enough about how WONDERFUL that effort is for the construction of these boards!  A difficult document to produce, and so far has been flawless, a great hand holder, and for those of us cautious and a little worried, it has been a great boon to my organization, making sure that things go on in the right order and no missteps along the way.  Marvelous.  A fantastic contribution to the project, and I'm sure that those who may choose to not embark on setting up their own station would do well and finish with this document. That said, if you've never soldered nor have the space to set up a work area to do this assembly with proper light and magnification, you still might see if there is a youthful pair of eyes connected to a body that works on electronics and all, to help you with this.

And, get a very nice pair of flush cutting, side style (CG Electronics has a nice one for about $5) nippers to take the leads off after soldering.

Can you tell I'm excited?  Go, builders!

Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on April 16, 2014, 09:15:42 AM
Well Done and Well Said, Dale!
Here's another quick tip, that I used for those 'multiple' "polarized" components, like diodes: Clip a short bit off each anode lead before inserting... the shorter lead adds another 'double check' for proper insertion...

...and one secret to getting the rods tightly together with the shrink wrap is to gradually and gently alternate each end, use lower heat setting if available, to about 'half-shrink' and not complete the end shrinking until you've gradually alternated toward the center from each end to the same 'half-shrink'... then follow the same process, ends first, alternating to the center to full shrink... if you follow me.

Mike
Title: Re: My home-made ferrite antennas
Post by: corwyyn on April 16, 2014, 05:49:32 PM
...and one secret to getting the rods tightly together with the shrink wrap is to gradually and gently alternate each end...
Yes that's what I did Mike, worked quite well.  Hopefully I'll get the other antenna wrapped this next weekend (man twisting all that wire around those small diameter ferrites made my hands cry :( )
Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 16, 2014, 10:09:01 PM
Great suggestions by everyone!

I finally spend a couple of hours this afternoon building my 300mm x 7.5mm ferrite core antennas. With the great guidance from above, I completed both of them in less than two hours (and two beers along the way  \:D/). They are now on-line, although sitting in my noisy office and seem to be working nicely.

I did do a couple things that may make it easier for someone else building their ferrite antennas.

NOTE: I was not able to get 725 turns on my cores. I managed to get 675 on both cores. The measured resistance of the windings for both cores reads at 2.6 ohms.

I'll add some photos I took of my setup later.

EDIT: Forgot to add that they have not been inserted into the pvc piping as yet. Once I do that, I will also shield them.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on April 17, 2014, 07:57:52 AM
Don,
Nice.

I'm looking forward to the pictures.

Once they are in the PVC holders/protectors, you said you'll shield them.

As I have read and reread the stuff to make sure to avoid as many mistakes as I can, I see that the official documentation from Eron says that ferrites may not need shielding and to try them without.  Plus I see comments here from others that they've been able to get good results without shielding. 

I'd be interested in your results if you try them in their expected final location to see if they are going to require shielding or not.  I hope you try it before you just go ahead with that part of the antenna construction to see how they work naked....

Dale
 
PS  If I used two beers I would have had no clue how many turns I had on the core.  I guess I'm a cheap date.

I just filled the cores from top to bottom with turns and hope for the best.
Dale
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on April 17, 2014, 08:42:13 AM
# of turns?  Dunno... fer shur. I just started windin' about 1/2" from each end of core, and stopped a 1/2" from the other.
Thought there was maybe about 750 of 26awg.

Yeah, unshielded will work fine if you don't have a lot of E field interference... Unfortunately my EMI is mostly all H field, so E shielding makes no difference. Shielding is for Electric field interference. Antennas want the magnetic field.
Title: Re: My home-made ferrite antennas
Post by: dfroula on April 17, 2014, 09:13:33 AM
The shielding is not required, but it seems to help my noise floor some. You need to ground the system if you use the shields, or the foil on the tubes seems to couple electrostatic noise into the system! Mike is correct in that near-field inductive noise from house wiring and such will not be helped one bit by the shields. That was the mode of noise coupling that I was seeing from my furnace-motor - inductive coupling from house wiring of noise spikes at peaks of the AC cycle. That had to be cured at the source.

When I wound mine, I stuck a screwdriver in a vice, stuck the spool of wire on the screwdriver, started 5mm from one end and wound by twirling the rod until reaching 5mm from the other end. With a little practice, it's easy to get the tension between thumb and forefinger right to keep the windings from slipping. I pre-cut 4 pieces of electrical tape to secure the windings as I went along. It stops the "oh sh**" reaction when the cat bumps your hand and the coils spring free. I just leave the tape in-place for the final heat shrink layer. Beer helps reduce the tension on the winder - not sure about the coil!

Winding these puppies was a snap compared to my 4-foot, 6" diameter Tesla coil secondary. That was an experience!

Don
WD9DMP

Don,
Nice.

I'm looking forward to the pictures.

Once they are in the PVC holders/protectors, you said you'll shield them.

As I have read and reread the stuff to make sure to avoid as many mistakes as I can, I see that the official documentation from Eron says that ferrites may not need shielding and to try them without.  Plus I see comments here from others that they've been able to get good results without shielding. 

I'd be interested in your results if you try them in their expected final location to see if they are going to require shielding or not.  I hope you try it before you just go ahead with that part of the antenna construction to see how they work naked....

Dale
 
PS  If I used two beers I would have had no clue how many turns I had on the core.  I guess I'm a cheap date.

I just filled the cores from top to bottom with turns and hope for the best.
Dale
Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 17, 2014, 10:37:01 AM
I have to work this morning but will get the photos uploaded this afternoon after I get home. Yes, I also pre-cut some strips of electrical tape that I put on the windings every 100 turns to keep them from coming loose. Worked nicely. The photos will show you my little jig I made to hold the wire spool and the ferrite core assembly.

I considered setting-up my metal lathe in thread cutting mode and feeding the wire on that way at a very slow speed but decided it would be too much of a hassle getting it setup. Would have to experiment with TPI settings too but it would give a very nice, smooth and even result.

I have not assemble the antenna in the pvc nor has it been shielded. Will experiment with and without shielding to see what happens.
Title: Re: My home-made ferrite antennas
Post by: Silversword on April 17, 2014, 05:56:46 PM
Hi,

I finally got my ferrite antenna wound and heat shrunk.  Looking good so far.  I did not count the number of turns but started about a quarter of an inch from one end and finished it up about the same distance. I cut a PVC tubing to 14 inches and will stuff the antenna into the tubing maybe this weekend.  I plan to us some polyester backing that my wife uses for her quilts.  Hope that this will work out. Any comments on the polyester backing material?

Another guidance as to how to position the antenna when it is mounted.  Vertically or horizontally? Direction facing (NEWS)? Or does it make any difference?

Getting closer.  Now have to wait until that part to come from Egon to finish the controller board and not make the same mistake.

Regards,

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on April 17, 2014, 07:23:15 PM
Hi,

I finally got my ferrite antenna wound and heat shrunk.  Looking good so far.  I did not count the number of turns but started about a quarter of an inch from one end and finished it up about the same distance. I cut a PVC tubing to 14 inches and will stuff the antenna into the tubing maybe this weekend.  I plan to us some polyester backing that my wife uses for her quilts.  Hope that this will work out. Any comments on the polyester backing material?

Another guidance as to how to position the antenna when it is mounted.  Vertically or horizontally? Direction facing (NEWS)? Or does it make any difference?

Getting closer.  Now have to wait until that part to come from Egon to finish the controller board and not make the same mistake.

Regards,

--Stan Y.
   Maui, Hawaii

Horizontal - 90 I do have mine oriented NS, but direction doesn't matter. I think most of us tend to orient ours NS, or in general relationship to storm activity overall.  See attached.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on April 18, 2014, 12:03:04 AM
I like the 'breadboard' cutting board approach!

I see you must have terminated the magnet wire to those colorful other wires coming out to the amplifier board.  Did you just get some fine stranded #22 or #20 and do a little solder/heat shrink to bring them out to the amp board, a little more robust than just bringing magnet wire out I assume.

I'm GPS locked and getting 8/8 satellites, and the board is bitching that I've not an amplifier connected nor to the router, but I'm too tired to push on tonight.  Antennas definitely need connecting tomorrow early.

Is regular patch cable CAT5 OK to run to the controller for testing?

Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 18, 2014, 12:42:02 AM
Dale,

You need to use "shielded" cat-5 cabling between the amp and controller boards as well as to the router to eliminate any potential interference. I tried unshielded initially (because I had over 500' of it). It did not work for me.
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on April 18, 2014, 05:56:56 AM
... 'breadboard' cutting board approach!
Actually, that is the 'permanent' operating setup! Been running just as you see it since August 2013. (except originally I had 120mm ferrites mounted on the cutting board itself. Cardboard added to support the longer antennas).
Quote
I see you must have terminated the magnet wire to those colorful other wires coming out to the amplifier board.  Did you just get some fine stranded #22 or #20 and do a little solder/heat shrink to bring them out to the amp board, a little more robust than just bringing magnet wire out I assume
What you see is the magnet wire itself... the 'color' is simply the insulation that was stripped off pieces of telephone wire, pushed over the magnet wire. The black wire has a splice in it because I inadvertently cut the ground wire too short when I wound the antenna  :oops:
Quote
Is regular patch cable CAT5 OK to run to the controller for testing?
No. as Don said, you must use ground shielded. In my case, wanting it quickly and half frustrated at my environmental EMI, I was only able to come up with shielded CAT6, in the 50' length I needed to the controller...also stayed with CAT6 shielded to the router. The controller is 'semi-permanently' grounded to the F connector on my cable modem, experimenting in my noisy situation proving that more effective.
Title: Re: My home-made ferrite antennas
Post by: dfroula on April 18, 2014, 01:51:26 PM
I found that shielded CAT5 from the controller board to the router is not needed. Also, if you ground the controller through the grounding terminals on the board and connect a shielded cable between the controller and router, there is the potential to create a ground loop, which could actually increase the noise.

In my setup, the Ethernet socket in the wall does not have a ground connection to the Ethernet switch in the basement, so that is not an issue. It might be an issue if you plug directly into an Ethernet switch or router that grounds the shield of the Ethernet cable. You would have two ground paths that could introduce a voltage difference between the two and unwanted ground currents in the controller.

I would stick with unshielded CAT5 for the network connection which eliminates the possibility of ground loops, and use the grounding terminals on the board to make the single ground connection.

Don
WD9DMP

Dale,

You need to use "shielded" cat-5 cabling between the amp and controller boards as well as to the router to eliminate any potential interference. I tried unshielded initially (because I had over 500' of it). It did not work for me.
Title: Re: My home-made ferrite antennas
Post by: Dr Obbins on April 18, 2014, 04:02:56 PM
FYI - Unshielded in use here from antenna in the attic through the walls of a two story house and into the basement garage connecting to the controller.
Title: Re: My home-made ferrite antennas
Post by: dfroula on April 19, 2014, 07:35:14 PM
Dave, it looks like your noise issues are under control. Your station stats look great.

Don
Title: Re: My home-made ferrite antennas
Post by: Dr Obbins on April 19, 2014, 08:09:16 PM
I am sure good craftsmanship may have had something to do with it also. UU While I don't live in the "middle" of nowhere, you can see it from here. This helped because all the noise issues were coming from my house and I didn't have to worry about neighbors or near by factories. I turned down the output on the invisible fence and changed out 2 dimmer switches with normal light switches.

The antenna was laying on the insulation in the attic between two foil wrapped HVAC return ducts. So it is now mounted about 1' from the peak of the attic roof. This also gets it above the exterior brick walls. I guess we will see how it likes the heat in the summer. The attic has a ridge vent that runs the length of the roof, so I am hoping it won't be that bad.

With out any local storms, the gain is cranked up to catch far away storms. On Monday we should get some more local storms and it may need to be backed down a bit. Not that I am complaining about the 70* temps with 30% humidity we are having.  :-)

For those of you who are building your antennas, Don's advice must be good advice. I have been watching and more often than not - of the top 10 long range stations he built 3 of them.
Title: Re: My home-made ferrite antennas
Post by: Silversword on April 19, 2014, 10:51:36 PM
Hi,

Attached is what I have done with my ferrite antenna construction so far.

The parts are just laid out for assembly.  The cotton like material is the sample batten from my wife's extra from her quilt making that I will use as the stuffing. The terminal barrier strip is what I plan to us inside the "L" enclosure to wire the copper wires from the antenna then to the shielded audio cable that will be connected to the amplifier.  I marked the copper wire coming from the loosely wound wire with Sharpie black pen for ID.

Coming along.  Still waiting for a part from Egon to finish the controller board.

Any comments welcome.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: DaleReid on April 19, 2014, 11:09:36 PM
I am like you, and worked on several portions of the project when time allowed and some things were more fatigue sensitive than others.

One thought... I have the L box as yo do, too, and wonder if the cover for the box is the best place to attach the terminal strip?  I assume we'll not be taking it on and off very frequently, but to put the strip in the bottom of the box, so it stays with the ferrites and the cover could be laid down anywhere rather than dangle might be worth a consideration?

Also, I see a lot of short runs from the ferrites to the amplifier, with no shielding.  Me being no expert by my recent questions, I wonder if it will be worth the trouble to do the change over from magnet wire to shielded heavier wire.  I plan on making some sort of box immediately adjacent to the L antennas, and think a few inches run to the inputs won't hurt a thing.  Especially if you look at the nice boxes with plexiglas covers, so one can see all the blinking lights.  Must   stare   at   blinking   lights.  Oh, yeah.  I am thinking of soldering the enamel coated magnet wire to a little pin connector, sort of like what the fancy audio guys have or a bigger Amphenol pin to be able to stick it in the antenna screw down, although others here say that doubling back the wire and tinning it makes it thick enough to grab well in the screw clamp.

I used some cotton pledgets from Walgreens that were meant to be for taking make-up off (mine is applied so seldom lately) that we had around the house.  Based on what one member here told me, be sure to have one support mid-ferrite to  keep the center from bending when both ends are supported.

Title: Re: My home-made ferrite antennas
Post by: Silversword on April 20, 2014, 12:56:58 AM
Hi,

Thanks Dale for your comments.

I was planning to mount that terminal strip on the back inside opposite the cover because if it was mounted on the other two sides, it would be very difficult to screw the leads on them.

I should look for a 5 terminal strip for ground if I need to shield the cores.  Just another thought.

I was also planning to wrap the whole ferrite antenna with the batting and not worry about sagging or putting more strain on those rods.  It has two shrink tubing.  The first one on the core, wrapped the wire and the second over that.  It seems to be quite ridged.

Regards,

--Stan Y.
   Maui, Hawaii
 
Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 21, 2014, 03:21:23 PM
Sorry for the delay in getting these photos posted...

The first image shows the setup I used to assemble the cores and shrink-wrap the unwrapped cores. I used 1/2 of a piece of 1/2" PVC pipe to hold the cores while I was heat-shrinking. It worked better than I had expected. All I had to do was to rotate the shrink-wrap tubing as it shrunk. I started at each end working my way towards the center. There was no problem with any bubbling in the center because I slowly shrunk it down in stages as I went from end to center.

The second photo shows the Harbor Freight heat-gun I used. It worked great and also has a cool-down feature.

The third photo shows the core winding jig I made out of some scrap 2x4 boards and a piece of 1/2" dowel. I also drilled two 1/2" holes in the edge of the 2/4 to place the dowel on one end and another to hold the ferrite core assembly while I wound it. The 26AWG magnet wire fit over the dowel and worked nicely. I did have to watch that the wire didn't start unspooling but it was not a problem. NOTE: I used a piece of painters tape to hold the loose end of the wire so it didn't get in my way during the winding. I just wrapped it around the end of the core and then straightened it out once I was done.

The fourth photo shows the finished cores and amp board laid out on my wife's quilting board.

The next step will be to prepare the cores for insertion into the L-box and the pvc piping. I'll do that once i find a quiet spot for the antenna.
Title: Re: My home-made ferrite antennas
Post by: dfroula on April 21, 2014, 03:36:25 PM
Nice job!

I really like the winding jig idea.

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 21, 2014, 03:56:10 PM
Nice job!

I really like the winding jig idea.

Don
WD9DMP

Thanks! The jig allows you to stop and take a break without worrying about the windings coming undone. If I were to make another I would tilt the dowel a little so there is not such a large angle created when the wire comes off the spool. I think it would make it less likely for the wire to come loose while winding.
Title: Re: My home-made ferrite antennas
Post by: Silversword on April 21, 2014, 04:36:06 PM
Hi,

Don, nice jig for the winding the ferrite antenna.  I would have mounted the assembly horizontally.  Make the wire come off the bottom of the spool and wind the core with both hands away from you.  That way you could put some tension on the spool and keep the winding kinda tight.  I did mine that way and it took me only about 20 minutes to wind one antenna. I used a towel under the cores to protect it it from the table that I was using.  I also used my wife quilting table to do the windings.

--Stan Y.
   KH6HHG
   Maui, Hawaii
 
Title: Re: My home-made ferrite antennas
Post by: W3DRM on April 21, 2014, 04:51:34 PM
Hi,

Don, nice jig for the winding the ferrite antenna.  I would have mounted the assembly horizontally.  Make the wire come off the bottom of the spool and wind the core with both hands away from you.  That way you could put some tension on the spool and keep the winding kinda tight.  I did mine that way and it took me only about 20 minutes to wind one antenna. I used a towel under the cores to protect it it from the table that I was using.  I also used my wife quilting table to do the windings.

--Stan Y.
   KH6HHG
   Maui, Hawaii

Hi Stan,

Well I guess there are many ways to accomplish the same end result. I followed what was described in an earlier post but added the jig (it was laying around the shop) to give me a bit of control while winding. I turned the core form with one hand (clockwise looking from the top end) and guided the wire onto the core with the other. That way, I could keep good tension on the wire coming off the spool and also keep it lined-up as I went along. The big advantage using the jig was that it allowed me to stop and take a break along the way without worying about things coming undone.

Your way sounds good too.
Title: Re: My home-made ferrite antennas
Post by: dfroula on April 21, 2014, 09:07:15 PM
My biggest problem winding the cores was two large cats perched next to the spool of wire, taking occasional swats at the shiny wire thingy flipping around at the end of the ferrite rod. They were convinced I was constructing a high-tech cat toy for their amusement.

The XYL's quilting hobby seems to have been a valuable resource! I like the quilting pad idea to cushion the ferrites. It beats toilet paper by a long mile!

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: Silversword on May 05, 2014, 06:35:07 PM
Hi All,

Still working on this part of this project.  Photos of termination and packing the antenna with quilt batting for the ferrite to the final construction are attached.

Any comments?

Finally got the broken part replaced so I can now continue with the controller board when time permits.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on May 05, 2014, 06:42:56 PM
Hi All,

Still working on this part of this project.  Photos of termination and packing the antenna with quilt batting for the ferrite to the final construction are attached.

Any comments?

Finally got the broken part replaced so I can now continue with the controller board when time permits.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii

Go, Stan, Go!  good job!
Title: Re: My home-made ferrite antennas
Post by: W3DRM on May 06, 2014, 04:19:58 PM
Hi All,

Still working on this part of this project.  Photos of termination and packing the antenna with quilt batting for the ferrite to the final construction are attached.

Any comments?

Finally got the broken part replaced so I can now continue with the controller board when time permits.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii

Great job Stan!

I wound up using some small bubble-wrap and electrical tape to hold it on the cores while I pushed it inside the 3/4" pvc pipe.

Once I got everything connected, I noticed I still wasn't wasn't getting much in the way of usable signals and there was a lot of noise. I then attached some ground wires from the shield that was wrapped around the pvc to the ground side of the antenna connection and voila, I had an immediate decrease in noise. When looking at the stats for my system, I've always been at or near to the bottom of the list. Within 15 to 20 minutes, I moved up the list and am now seeing a huge improvement in my numbers (see below):

So, in my case, grounding the shield of the ferrite cores, has made a significant improvement in my data. And, on the Overview map, I am now seeing lots of strikes being shown for my station where previously, I'd see none or at most 2 or 3.

And lastly, my ferrite antenna is currently sitting in my very noisy office with three computers running all the time. Once I receive and build the new E-file kits, I'll be moving everything outside away from the house which I am hoping will improve things even further.
Title: Re: My home-made ferrite antennas
Post by: DaleReid on May 06, 2014, 06:10:21 PM
Don,
Glad the grounding of the shields did the trick.

A couple questions:  Did you have the shields on the PVC as someone had posted, but NOT grounded them yet?

Did you have crappy efficiencies and noise and then placed the shields and did the grounding?

Did you run a ground from the shields in to attach to the ground terminal on the pre-amp board or ground outside that?

I just got some copper tape and hope to get things installed by this weekend since the trees with Oak Wilt are down and I hope to have some me time to work on this project further.

Thanks for the extra info.

Dale
  (I've always been wondering if I can put the shield tape on the pvc pipe when it is easy to access, and then ground later if I need to, or if it will goof things up by putting the wrap on the PVC and not grounding it to see what efficiencies I get with a different location.
Title: Re: My home-made ferrite antennas
Post by: W3DRM on May 06, 2014, 09:00:09 PM
Don,
Glad the grounding of the shields did the trick.

A couple questions:  Did you have the shields on the PVC as someone had posted, but NOT grounded them yet?

After I built the ferrite antennas, I did not put them in the pvc right away because I wanted to see how they worked. A couple of days ago, I added the pvc pipes but did not shield them - again, wanted to see if there was any difference - there was not. So, I added the shielding. I used the same adhesive aluminum tape I had used for my V2 Loop antenna leaving a small slit along one side of the pvc. I did not attach any ground but it was soon apparent that my signals had dropped to almost zero and the noise levels went sky-high.

Quote
Did you have crappy efficiencies and noise and then placed the shields and did the grounding?

Yes, see my comment above. I added the grounds today and have been blown away by the change I am seeing.

Quote
Did you run a ground from the shields in to attach to the ground terminal on the pre-amp board or ground outside that?

The grounds are attached to each of the pvc pipes using another piece of the adhesive aluminum tape to hold the wire against the shield. That wire then goes to the ground-side of the atenna input terminals. There is one for each of the ferrite assemblies. BTW, I used some leftover 26AWG wire that I used to wind the ferrites with for the ground wires.

Quote
I just got some copper tape and hope to get things installed by this weekend since the trees with Oak Wilt are down and I hope to have some me time to work on this project further.

Thanks for the extra info.

Dale
  (I've always been wondering if I can put the shield tape on the pvc pipe when it is easy to access, and then ground later if I need to, or if it will goof things up by putting the wrap on the PVC and not grounding it to see what efficiencies I get with a different location.

I think the ungrounded shield actually acted as an antenna and picked up a lot more noise. Once I added the grounds, the noise dropped dramatically. I am currently seeing 47mvpp noise floor on the A channel and 46mVpp on the B channel. Prior to adding the grounds, it was around 120mVpp on each channel. That is a major drop in noise levels and was probably the cause of my poor performance.

I can't wait until I get the E-field kits so I can relocate everything outside and away from my noise sources.

Good luck with your setup. Hope these answers have helped.
Title: Re: My home-made ferrite antennas
Post by: dfroula on May 06, 2014, 09:05:52 PM
Both Jim McMurry and I had the same experience - the ungrounded shields pick up MORE noise than leaving the ferrites unshielded.

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on May 06, 2014, 09:18:26 PM
Both Jim McMurry and I had the same experience - the ungrounded shields pick up MORE noise than leaving the ferrites unshielded.

Don
WD9DMP
And, back in the old garage sweet spot location, shielding helped not at all with the 300mm ferrites... just decreased over-all signal and noise level.  My weird location seems to prefer non-shielded since most if not all my noise is H field related. Strange...but that's the way it is here!  Arrrrggghhhh....
Title: Re: My home-made ferrite antennas
Post by: DaleReid on May 11, 2014, 07:52:55 PM
Well, I'm going to bite the bullet and apply copper tape shield to my ferrites tonight or tomorrow.

Having too much fun watching the real time display as those storms rumble by.

I know some here have NOT gotten benefit, I guess I could try to remove the copper (expensive) foil if it doesn't help any.

Question:

Is there a preferred orientation for the break in the surrounding shielding material?  Is it best to have the open notch vertical up, vertical down (rain won't run in the break and get under the adhesive), facing one or the other horizontal planes?

I assume since it was done that way in the project that each shield should have it's own separate ground wire run back to the amplifier board and under the ground screw with the associated wire from the ferrite?  I was thinking just run one wire to a shield, jump to the other shield.  Not that I'm short on wire, but why do more than needed?  I see the ground screw is on the same ground plane as the other one on the board.

If some of you guys can tear yourself away from the screens, I'd appreciate it.

Dale


Title: Re: My home-made ferrite antennas
Post by: scarecrow93 on May 11, 2014, 08:43:45 PM
Dale-

I don't think it matters much.  I have my notch pointed toward the horizon.  My setup was only made for use inside the house.

If you're worried about rain getting under the adhesive, what about putting the completed antenna inside another, unshielded PVC pipe?  Maybe there is a rubber grommet or some other spacer you can use between the completed antenna and the outer PVC pipe.  That way you know the rain is a non-factor.

Just my .02   :grin:

Lance
#724 - Owings, MD
Title: Re: My home-made ferrite antennas
Post by: dfroula on May 12, 2014, 09:53:44 AM
Electrically, the orientation of the gap matters not.

As for shield grounding, I have tried several configurations while trying to find a solution to my AS3935 detection issues.

I originally had the shield grounds tied to the "-" wire of each antenna from their respective shields. I also tied the grounded pair to the drain wire of the shielded cable I use to connect the antenna assembly to the amp board. At the amp, the drain wire and "-" antenna lead from each antenna are tied to the grounded "-" side of the amplifier inputs. Don't tie the grounded leads to the input connection of the amps or you will have all sorts of weird noise pickup!

I also tried separating the shield grounds from the antenna ground, running a separate ground just to the shields, and leaving the rest of the system without an explicit ground. DON'T DO THIS!!!!!! The noise pickup was incredible because of the potential difference between the shields and the rest of the system.

I finally just re-grounded the controller, took the single common shield ground wire I had installed at the antennas and reconnected the single wire to one of the "-" terminals at the amp input. This worked just as well as my original "dual-ground" setup and returned normal operation.

None of theses ground configurations caused my AS3935 to start detecting lightning, however!

Regards,

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: DaleReid on May 14, 2014, 09:17:20 PM
This afternoon I decided to bite the bullet and get the ferrites shielded.

I used a wrap of copper foil tape, soldered the ground wire to each of the clever tabs I made, and ran the wire from each shield into the box and firmly but gently placed the tinned wire end under the - terminal.

I guess I was hoping for more.  Still get the burst of some noise once in awhile.  Gone into interference a couple times already.  The automatically controlled gain may be running higher numbers than I've seen for extended periods, but hard to know in just this short while.

I will try to get the E-field antenna together when it arrives and functioning well before I move things out to the shed, where I hope to find a quieter environment.

Nonetheless, as I try to get a relatively well thought out area to put the antennae, I have a couple of questions:

First, is there a way to 'plug into' the amplifier board and wander around sort of listening to it to see if the apparent noise fades or an intermittent local noise can be minimized?  I thought I saw somewhere that one of the participants was using an ear bud to listen for a good spot.  Maybe it was too much Cutty, although the Coors may have had something to do with it too.   Dunno.  But I cannot find that reference again, if there was something like this being done to listen to local noise.

Second, the auto gain function seems to be way better than the manual yellow LED setup, but since the system varies the gain all over the place, and other than looking at the Controller Board generated web page to see what the values are, I don't know of a handy little graph that Tobi generates that would allow one to look back, say two to six hours, and see a plot of what the gain settings were over that period.  I would think this might be helpful to see, in addition to the efficiencies, how much the gain can be elevated, and hence the relative quietness of the session.

There are graphs up the yazoo, so I would think that something like this may have been done and just isn't particularly obvious to me.  On the other hand, maybe this info is of zero value.

Thanks.
Title: Re: My home-made ferrite antennas
Post by: jmcmurry on May 15, 2014, 08:11:18 AM
Second, the auto gain function seems to be way better than the manual yellow LED setup, but since the system varies the gain all over the place, and other than looking at the Controller Board generated web page to see what the values are, I don't know of a handy little graph that Tobi generates that would allow one to look back, say two to six hours, and see a plot of what the gain settings were over that period.  I would think this might be helpful to see, in addition to the efficiencies, how much the gain can be elevated, and hence the relative quietness of the session.

Dale,

Not a graph, but I have a php script that I have running each minute that creates a log entry whenever there's a gain change on either channel, or a change in status.  The attached shows the log in action and you'll also see where my ISP went down for 1.5 hour at midnight.  If that would be useful I can clean it up, zip it and post a copy later today.

- Jim
Title: Re: My home-made ferrite antennas
Post by: dfroula on May 15, 2014, 08:32:24 AM
I've installed a 1/8" stereo jack on all the amplifiers I have built. The jack is connected to the test output pins as follows:

sleeve---Gnd
TIP------Amp 2 signal
RING-----Amp1 signal

This puts channel 1 in the right ear and channel 2 in the left.

You cannot plug low-impedance earbuds or headphones directly into the jack, as they will load the amplifier too much and stop detections. You need to plug a stereo amplifier into the jack and the headphones into that. I built a battery-powered stereo "CMOY" stereo amp for the purpose.

You could conceivably unplug the amp from the controller, rig a 5-volt battery supply, manually adjust the gain with the pot, and walk around the house listening for a low-noise spot.

Nerd alert: This will make your friends and family think you have gone over the edge!

It does work, however.

Regards,

Don
WD9DMP

First, is there a way to 'plug into' the amplifier board and wander around sort of listening to it to see if the apparent noise fades or an intermittent local noise can be minimized?  I thought I saw somewhere that one of the participants was using an ear bud to listen for a good spot.  Maybe it was too much Cutty, although the Coors may have had something to do with it too.   Dunno.  But I cannot find that reference again, if there was something like this being done to listen to local noise.
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 03, 2014, 11:06:11 AM
OK, after reading all of this thread, I now know how to make a 300mm antenna.

But here's what I haven't seen in this thread.  What advantages are you guys with the longer antennas noticing?  On good days, I'm reaching pretty well with my 200mm.

So lower noise?  Better range?  Are you having to drop the amplification down due to longer antenna?

I'm just trying to see if the antenna change is worth the effort.  TIA
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 11:08:53 AM
I have nothing to compare it with, but I went with Mike's 300mm, ~700 turn design (double heat shrink tubing).  After adjusting a few things, I'm detecting strikes at more than 3000 km nearly out of the box (before decent siting, packaging, grounding etc.).
Title: Re: My home-made ferrite antennas
Post by: dfroula on June 03, 2014, 11:52:11 AM
Longer ferrite = more gain in the antenna and less needed at the amplifiers, resulting in better signal-to-noise ratio. That means longer distance detection.

There is a limit, however. Too much antenna gain will increase the sensitivity to local noise sources as well. Also, too long an antenna may drop the self-resonance of the antenna into the range used by the amplifier filters. This may distort the waveforms to the point that the system can no longer assign an accurate time stamp to a strike. Our antennas need to operate broadband, with low-Q - The opposite of a regular narrow-band radio receiver antenna.

The 250x7.5 mm antennas have test data to show the self-resonance range is well above what is used by the amp filters, so no issues.

The 300x7.5 mm antennas have not been characterized, but they seem to be working just fine as well for those who are using them..

That is using 26awg magnet wire, which is HIGHLY RECOMMENDED, as the tests were conducted with that gauge and the resulting number of turns.

Best regards,

Don
WD9DMP

OK, after reading all of this thread, I now know how to make a 300mm antenna.

But here's what I haven't seen in this thread.  What advantages are you guys with the longer antennas noticing?  On good days, I'm reaching pretty well with my 200mm.

So lower noise?  Better range?  Are you having to drop the amplification down due to longer antenna?

I'm just trying to see if the antenna change is worth the effort.  TIA
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 12:01:20 PM
I believe my unshielded 300mm, 7.5mm are slightly more immune to the H field noise in my environment, while at the same time increasing the signal somewhat. I don't have equipment to measure. That's in comparison to the originals I ordered with the kit... Mine are oriented N/S E/W for several reasons, mostly because that's how I want them  :twisted:
I think my most distant strike detected was close to 4800km, back when Don F and I were the only two reds, and in 'serious bloody competition'  ;) over who was #1.... and the nearest just about 7Km, if I remember correctly.
(But this isn't really about distance... we should all remember this is about network efficiency)
When I attempted shielding, my initial impression was that the 'noise basement' had dropped about 10 db.  That was purely coincidental and situational, and proved not to be the case. Eventually I became convinced that the overall performance had degraded because of it, and removed the shielding.

My gains on H field are typically 10x10 both channels, depending on the axle factory's welders and assembly lines south of me. Then A needs to about 8x8 or 8x5, depending. My thresholds typically are 100-120 (without channel mapping) in either or both channels. With Channel mapping, because of the E field addition, I've been running them at 100-110. If old axle factory runs a second line, especially at night, I bring 'em to 120.

Nothing bothers my E fields... once in awhile a lawn mower, or some other thing that arcs nearby, might cause a burst of interference... only other way to get to interference mode is with simply too many signals. With my 370mm (15") probe, I'll have to knock gain all 3 channels down to 2x1 or even 1x1 and still detect strikes 200-300 mi away with E field alone, and H field at 1x1. I've run E field at 8x8 all channels, but typically will run at about 5x5, which is still too high for <300 miles and thresholds are always at 90.
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 12:05:46 PM
Longer ferrite = more gain in the antenna and less needed at the amplifiers, resulting in better signal-to-noise ratio. That means longer distance detection.

There is a limit, however. Too much antenna gain will increase the sensitivity to local noise sources as well. Also, too long an antenna may drop the self-resonance of the antenna into the range used by the amplifier filters. This may distort the waveforms to the point that the system can no longer assign an accurate time stamp to a strike. Our antennas need to operate broadband, with low-Q - The opposite of a regular narrow-band radio receiver antenna.

The 250x7.5 mm antennas have test data to show the self-resonance range is well above what is used by the amp filters, so no issues.

The 300x7.5 mm antennas have not been characterized, but they seem to be working just fine as well for those who are using them..

That is using 26awg magnet wire, which is HIGHLY RECOMMENDED, as the tests were conducted with that gauge and the resulting number of turns.

Best regards,

Don
WD9DMP


Not to mention that going much larger/longer for ferrites is a needless increase in cost and space requirements.  The system as it is is more than sensitive enough for long-range detection with 250-300 mm long ferrites.

Once you're using that length/gain of H-field antenna, you're probably better off trying to reduce noise sources directly.
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 12:09:36 PM
Longer ferrite = more gain in the antenna and less needed at the amplifiers, resulting in better signal-to-noise ratio. That means longer distance detection.

There is a limit, however. Too much antenna gain will increase the sensitivity to local noise sources as well. Also, too long an antenna may drop the self-resonance of the antenna into the range used by the amplifier filters. This may distort the waveforms to the point that the system can no longer assign an accurate time stamp to a strike. Our antennas need to operate broadband, with low-Q - The opposite of a regular narrow-band radio receiver antenna.

The 250x7.5 mm antennas have test data to show the self-resonance range is well above what is used by the amp filters, so no issues.

The 300x7.5 mm antennas have not been characterized, but they seem to be working just fine as well for those who are using them..

That is using 26awg magnet wire, which is HIGHLY RECOMMENDED, as the tests were conducted with that gauge and the resulting number of turns.

Best regards,

Don
WD9DMP

OK, after reading all of this thread, I now know how to make a 300mm antenna.

But here's what I haven't seen in this thread.  What advantages are you guys with the longer antennas noticing?  On good days, I'm reaching pretty well with my 200mm.

So lower noise?  Better range?  Are you having to drop the amplification down due to longer antenna?

I'm just trying to see if the antenna change is worth the effort.  TIA
Don gives us some very specific info here... and he's dead right.  If you check efficiencies, (right now all our eyes seem to be on distance,) and look closely, his antenna suggestions consistently come in way up there. Best over all might actually be Jumpin' Joe's 12 ball loop.
But 'detection at distance' isn't the best critera for the network. look on your station page, at your 'locating ratio'.... we get everybody consistently to around 20-40% we've got a good network... when it's low, below 10 especially, we're sending too many signals compared to strokes detected. There are any  number of reasons for this, but most of it is because we're running higher gains than a more denser network would require. And missing some percentage of nearer signals because of the clutter this produces.
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 12:16:17 PM
oops... change "detection ratio' to "locating ratio" in the above...
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 03, 2014, 12:17:20 PM
OK, a lot of that makes sense.

What I'm noticing on my 200mm is that on a good day, I can run 10x10.  On those days, I'm getting close to 1300 miles of detection.  I've seen strikes into Mexico and off the ocean by Delaware, from North Dakota.  A lot farther than I expected.

But other days, I have to drop the settings down to 10x5 or even 10x4 to get out of interference.  Then my EF ration drops to 20% or less.  Today is a good day, I'm running 67%.  But I just had to drop my numbers from 10x10 this morning to 10x5 again.

So with a longer antenna, I probably won't be running 10x10, probably 10x8 or so.  But still needing to drop that number down during interference.  That's basically the info I'm looking for.
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 03, 2014, 12:18:13 PM
BTW, I'm still waiting for my E-Field to arrive...
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 12:21:33 PM
OK, a lot of that makes sense.

What I'm noticing on my 200mm is that on a good day, I can run 10x10.  On those days, I'm getting close to 1300 miles of detection.  I've seen strikes into Mexico and off the ocean by Delaware, from North Dakota.  A lot farther than I expected.

But other days, I have to drop the settings down to 10x5 or even 10x4 to get out of interference.  Then my EF ration drops to 20% or less.  Today is a good day, I'm running 67%.  But I just had to drop my numbers from 10x10 this morning to 10x5 again.

So with a longer antenna, I probably won't be running 10x10, probably 10x8 or so.  But still needing to drop that number down during interference.  That's basically the info I'm looking for.
Remember that 'efficiency' rating on the 'Participants' page is "network overall"... if all the storms are in Washington State, you'll have a very low percentage, but our West Coast stations, normally toward the bottom, will jump way the heck up there. Besides antennas, a big reason middle US stations are consistently up there is simply due to location.
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 12:28:59 PM
OK, a lot of that makes sense.

What I'm noticing on my 200mm is that on a good day, I can run 10x10.  On those days, I'm getting close to 1300 miles of detection.  I've seen strikes into Mexico and off the ocean by Delaware, from North Dakota.  A lot farther than I expected.

But other days, I have to drop the settings down to 10x5 or even 10x4 to get out of interference.  Then my EF ration drops to 20% or less.  Today is a good day, I'm running 67%.  But I just had to drop my numbers from 10x10 this morning to 10x5 again.

So with a longer antenna, I probably won't be running 10x10, probably 10x8 or so.  But still needing to drop that number down during interference.  That's basically the info I'm looking for.
Remember that 'efficiency' rating on the 'Participants' page is "network overall"... if all the storms are in Washington State, you'll have a very low percentage, but our West Coast stations, normally toward the bottom, will jump way the heck up there. Besides antennas, a big reason middle US stations are consistently up there is simply due to location.

As they say, "location, location, location".  Try telling your spouse and your realtor that you need to find a house with good lightning detection characteristics the next time you go hunting.  See how that goes over :)
Title: Re: My home-made ferrite antennas
Post by: DaleReid on June 03, 2014, 12:45:26 PM
Mark,
I beg to differ with you.

The reason that us MidWesterners are frequently high on the efficiency list is cuz we're such cool dudes.

Nothing at all to do with location.

"I don't often invite interference, but when I do, its Dos Equis..."

Now if I can just get my Efile done.

Title: Re: My home-made ferrite antennas
Post by: dfroula on June 03, 2014, 01:00:08 PM
This is just an empirical observation, from when I had Dave R's station running here (300 mm ferrites), comparing to my 250 mm antennas. It seemed that the longer antenna's exhibit greater directivity. I am somewhat concerned that carrying the "longer is better" philosophy too far may create some null area's in coverage at 45, 135, 225, and 315 degrees from the right-angle antennas. I know that when I have constructed tuned LF AM direction-finding ferrite antennas, "longer" usually also meant "more directional" and "sharper nulls".

Regards,

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: dfroula on June 03, 2014, 01:10:15 PM
On a quiet day with no nearby storms and relative low lightning density in North America, I can run 16x10 on both 250x7.5 mm antennas, both thresholds at the default 120mv with "Auto Adapt to Noise" on. I will usually run at 100% effective gains with those settings, indicating gain up to the max I have set.

I need to back down to 16x8 to stay out of interference mode if there are local storms or a high density of storms in North America. I rarely bother to adjust the gains any lower, and just ride out any storm-induced interference mode.

The "Auto Adapt to Noise" handles local noise sources fine, which in my case seem to come and go in the afternoon. These noisy periods result in lower effective gains, but rarely induce interference mode periods.

These settings seem to scale well with Mike's settings, considering the 50mm longer length of his antennas.

That old cigarette ad comes to mind - "...a silly millimeter longer..."  :-)

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 01:14:38 PM
This is just an empirical observation, from when I had Dave R's station running here (300 mm ferrites), comparing to my 250 mm antennas. It seemed that the longer antenna's exhibit greater directivity. I am somewhat concerned that carrying the "longer is better" philosophy too far may create some null area's in coverage at 45, 135, 225, and 315 degrees from the right-angle antennas. I know that when I have constructed tuned LF AM direction-finding ferrite antennas, "longer" usually also meant "more directional" and "sharper nulls".

Regards,

Don
WD9DMP

That might explain the "greater noise immunity" Mike noticed.

In another life, I did quite a bit of antenna modeling with NEC--though never anything with ferrites.  Let me see if there's something that can be done to simulate these things.
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 03, 2014, 01:15:30 PM
OK.  I'll have to fess up a bit here.  I have already made a 300mm test antenna set and used it for a couple of days.  But what I started noticing is exactly what Don was referring to.

On my 200, I was getting strikes in Wisconsin before.  But with the 300, much less strikes in that general direction.  I didn't know if it was due to my lower amp setting or what.  So I put the 200 back in last night.  And now it seems better.  But of course due to storms in SD, I'm having to back the amp down.

I bought more cores, so I might have to try to make a 250mm next.

Oh, BTW, my antennas are NW/SW arrangement.  But that's because my house is set that way.  And my OCD says the antennas have to match the walls in my garage.  They can't be crooked.  :-)
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 01:21:49 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.
Title: Re: My home-made ferrite antennas
Post by: Dr Obbins on June 03, 2014, 02:14:42 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.
This is just an empirical observation, from when I had Dave R's station running here (300 mm ferrites), comparing to my 250 mm antennas. It seemed that the longer antenna's exhibit greater directivity. I am somewhat concerned that carrying the "longer is better" philosophy too far may create some null area's in coverage at 45, 135, 225, and 315 degrees from the right-angle antennas. I know that when I have constructed tuned LF AM direction-finding ferrite antennas, "longer" usually also meant "more directional" and "sharper nulls".

Regards,

Don
WD9DMP

Not knowing all the  tech stuff as to why and how the antennas work, I will verify that my 2 channels behave differently. The "greater directivity" seems to fit the behavior I have seen. The one antenna seems to pick up more N-S and the other more E-W. With out having anything to compare the end results to, I can not confirm if more or less total strikes are registered.
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 02:19:29 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.
This is just an empirical observation, from when I had Dave R's station running here (300 mm ferrites), comparing to my 250 mm antennas. It seemed that the longer antenna's exhibit greater directivity. I am somewhat concerned that carrying the "longer is better" philosophy too far may create some null area's in coverage at 45, 135, 225, and 315 degrees from the right-angle antennas. I know that when I have constructed tuned LF AM direction-finding ferrite antennas, "longer" usually also meant "more directional" and "sharper nulls".

Regards,

Don
WD9DMP

Not knowing all the  tech stuff as to why and how the antennas work, I will verify that my 2 channels behave differently. The "greater directivity" seems to fit the behavior I have seen. The one antenna seems to pick up more N-S and the other more E-W. With out having anything to compare the end results to, I can not confirm if more or less total strikes are registered.

In theory, that's why you need two ferrites or loops at right angles to each other - one rod or loop has most of its gain in two opposite directions, with nulls at right angles.  Summing the gain patterns of both should give you relatively even coverage.

Of course, if your gain patterns are too directional, then you'd have uneven coverage, especially at 45 degrees off axis from both rods/loops.  I haven't yet seen whether I've noticed that (my station has been running jerry-rigged for about 18 hours).
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 03, 2014, 02:23:09 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.

Which graph are you using to see this?  I'd like to compare what I have to what now to when I put the longer antenna back in.

Thanks
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 02:24:43 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.

Which graph are you using to see this?  I'd like to compare what I have to what now to when I put the longer antenna back in.

Thanks

It's at the bottom of the page here:

http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=689&bo_station_id=33&lang=en&bouser (http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=689&bo_station_id=33&lang=en&bouser)

And here is yours:
http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=1002&bo_station_id=64&lang=en&bouser (http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=1002&bo_station_id=64&lang=en&bouser)

Jonathan
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 02:25:37 PM
 Generally, two loops,  will respond with signals thus
(http://ourspecial.net/twinhollies/weathercenter/blitz/sigs/sigsdir500.jpg)
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 02:40:16 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.

Which graph are you using to see this?  I'd like to compare what I have to what now to when I put the longer antenna back in.

Thanks

It's at the bottom of the page here:

http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=689&bo_station_id=33&lang=en&bouser (http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=689&bo_station_id=33&lang=en&bouser)

And here is yours:
http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=1002&bo_station_id=64&lang=en&bouser (http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=1002&bo_station_id=64&lang=en&bouser)

Jonathan
The BLUE lines indicate the cumulative directions,... and yes, mine are Highly directional... that's where the storms were located in relation to my station.

As far as I know, the 'green' indicates the general directivity of all stations in the network, summed together.

Of more importance is the figure up in the top: "location ratio" 24% meaning generally 24% of my signals were used to locate strikes. A network goal would be to have all stations in the 20-40% range.  (Yeah, sometimes my ratio is way down... yesterday for some time it was below 6%. I was sending a lot of signals, and had a high "efficiency" in detecting strikes on the participants chart, but the strikes were far away, and my station was not in the nearer 6 required for 'location'. Which might mean I'm sending a lot of un-necessary signals, at the expense of missing nearer ones that could be located.
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 03, 2014, 02:58:10 PM
One interesting point: Mike's "stroke ratio by bearing" graph on his lightningmaps station page (#689) doesn't seem to show a whole lot of directivity--assuming he's using the 300 mm ferrites currently.

Which graph are you using to see this?  I'd like to compare what I have to what now to when I put the longer antenna back in.

Thanks

It's at the bottom of the page here:

http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=689&bo_station_id=33&lang=en&bouser (http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=689&bo_station_id=33&lang=en&bouser)

And here is yours:
http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=1002&bo_station_id=64&lang=en&bouser (http://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=1002&bo_station_id=64&lang=en&bouser)

Jonathan
The BLUE lines indicate the cumulative directions,... and yes, mine are Highly directional... that's where the storms were located in relation to my station.

As far as I know, the 'green' indicates the general directivity of all stations in the network, summed together.

Of more importance is the figure up in the top: "location ratio" 24% meaning generally 24% of my signals were used to locate strikes. A network goal would be to have all stations in the 20-40% range.  (Yeah, sometimes my ratio is way down... yesterday for some time it was below 6%. I was sending a lot of signals, and had a high "efficiency" in detecting strikes on the participants chart, but the strikes were far away, and my station was not in the nearer 6 required for 'location'. Which might mean I'm sending a lot of un-necessary signals, at the expense of missing nearer ones that could be located.

Hmmm...I took it a little differently, though we might be talking about two different things.  Since the "stroke count" legend is in dark blue, the blue lines appear to be the total network stroke count by bearing in relation to the station in question...but the stroke ratio (a percentage) legend for a given station is provided in light green, and looks like it's also in terms of bearing from the station.  If green were general directivity summation of all stations, it should be the same for any station, but it's not.

In other words, it appears to me this graph provides 1) a circular graph of stroke count, indicating the bearing of the strokes detected by the network from a given station and 2) the percentage of strokes detected by the station, also in bearing.  To me, it looks like your station is pretty even in terms of stroke detection vs. bearing.

Most of the strokes over the last 24 hours have been to the WNW of your station, Mike, but of the strokes there have been in most directions, you've picked up high percentages of them.  If your ferrites were highly directional, I'd expect to see an emphasis on stroke detection in four orthogonal directions.

Of course, the graph of stroke ratio would be influenced by ionospheric propagation, as well as stroke power and relative distance of the strokes from a given station.

Jonathan
Title: Re: My home-made ferrite antennas
Post by: Dr Obbins on June 03, 2014, 08:43:06 PM
Generally, two loops,  will respond with signals thus
(http://ourspecial.net/twinhollies/weathercenter/blitz/sigs/sigsdir500.jpg)
Luckily, I happened to mount the antennas in the same basic orientation of Mike's "stroke ratio by bearing" graph. So Channel 1A is N-S and channel 1B is E-W.
North:
(http://www.cavecountryweather.com/Pictures/North.jpg)
South:
(http://www.cavecountryweather.com/Pictures/South.jpg)
East:
(http://www.cavecountryweather.com/Pictures/East.jpg)
West:
(http://www.cavecountryweather.com/Pictures/West.jpg)



Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 09:19:49 PM
Luckily, I happened to mount the antennas in the same basic orientation of Mike's "stroke ratio by bearing" graph. So Channel 1A is N-S and channel 1B is E-W.
Excellent Dave... !  Good analysis & illustration!  Dang, that's good... !

We're talking H field loops, here... not E field which is omni-directional...

Now you might see how to determine an interference source by direction,...
getting bearing on a line is simple... deciding on which half of the line is
a bit more difficult, since it can be difficult to determine exactly when the signal goes
positve or negative at the trigger,.... unless you can pull stunts like Dave did.... .

Remember that the direction and location is determined at the server,
related to time, based on curves, and intersection of those curves by
at least 5 other stations in the US, currently.

Dave. this might actually fit also on the interference thread, helping to find direction of
an interference signal,... pretty doggone good illustration of directivity of loops.
Well done, and Kudos!!!

Mike
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 09:35:17 PM
Of course, the graph of stroke ratio would be influenced by ionospheric propagation, as well as stroke power and relative distance of the strokes from a given station.
Jonathan
  I strongly suspect the algorithms at the server 'image' the initial ground wave when possible, rather than a sky wave reflection. Rejection of "earth/ionosphere waveguide" signals  when enough stations detect the initial ground wave and pre-charge pulses. Egon would actually have us detecting the 'pre-charge' elements, before the stroke itself, for better location accuracy. "TOGA" as opposed to "TOA" that the net has to operate with at the present time. "TOGA", as I understand, is pretty much ready to implement once stations and networks are adequately tuned and set up. And out of a combination of the two, I suspect, will arise 'polarity' 'type' and 'strength'. Hence the need for stations to have "shorter range" as opposed to "longer range", which would be possible in a denser network.
Title: Re: My home-made ferrite antennas
Post by: Dr Obbins on June 03, 2014, 09:36:25 PM
Quote
Excellent Dave... !  Good analysis & illustration!  Dang, that's good... !
One of those "Oops! I did something right"  :lol: moments.
Quote
this might actually fit also on the interference thread, helping to find direction of
an interference signal,..
Go ahead and link the pics over there if you like. You can probably explain whats going on better than me.  ;)
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 03, 2014, 09:38:14 PM
Quote
Excellent Dave... !  Good analysis & illustration!  Dang, that's good... !
One of those "Oops! I did something right"  :lol: moments.
Quote
this might actually fit also on the interference thread, helping to find direction of
an interference signal,..
Go ahead and link the pics over there if you like. You can probably explain whats going on better than me.  ;)
When I get some of that stuff called 'time"....
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 04, 2014, 05:51:36 AM
Of course, the graph of stroke ratio would be influenced by ionospheric propagation, as well as stroke power and relative distance of the strokes from a given station.
Jonathan
  I strongly suspect the algorithms at the server 'image' the initial ground wave when possible, rather than a sky wave reflection. Rejection of "earth/ionosphere waveguide" signals  when enough stations detect the initial ground wave and pre-charge pulses. Egon would actually have us detecting the 'pre-charge' elements, before the stroke itself, for better location accuracy. "TOGA" as opposed to "TOA" that the net has to operate with at the present time. "TOGA", as I understand, is pretty much ready to implement once stations and networks are adequately tuned and set up. And out of a combination of the two, I suspect, will arise 'polarity' 'type' and 'strength'. Hence the need for stations to have "shorter range" as opposed to "longer range", which would be possible in a denser network.

Well, I'm working with an ARRL official on the possibility of getting a writeup of the Blitzortung system and station construction in QST.  No idea on a timeframe (the guy is very busy), but I'm hoping it would help with station density in the U.S.

If it goes forward, I'll definitely put him in touch with anyone here who might want to contribute knowledge.

Also, I noticed something going through the raw data files last night...maybe others have noticed this before, too, and it's obvious...but, for strike listings in Europe, there are huge numbers of "low power" strikes (1-10 kA category), whereas in the U.S., nearly all strikes detected are above 10 kA.  I don't know how accurate the current levels calculated are (they seem low to me), but I think the point is, when people say the network in the U.S. is missing strikes, a big reason really is because lower powered strikes are simply not detectable by the minimum number of stations needed to locate them, without a more dense network.

Another reason why we need more stations in the U.S. :)
Title: Re: My home-made ferrite antennas
Post by: steel_edges on June 28, 2014, 09:34:20 AM
I would like to chime in with my experience building up these ferrite antennas.  I decided to make the 300mm length ferrites using the rods from Nebraska Surplus mentioned earlier in this thread.  The adhesive used was a machinable JB-weld type of epoxy that requires 24 hrs to fully cure.  After they were cured I covered them with 3/8" heat shrink, I guess I was too aggressive with the heat gun because just as the first rods heat shrink was almost complete I felt one or more if the glue joints fail. It worked out fine, once it cooled it was still very rigid and it did not cause and issue with winding.

The second rod went much better, I was more careful applying heat, taking breaks to allow things to cool, also holding the rod vertically helped keep the adhesive intact. I wound the rods with 28AWG wire because I already had a spool laying around. I then applied a final heat shrink layer of 1/2 material being careful with the heat like before.

After everything cooled down and I compare the two rods I cannot tell which one had the glue failure, they are both quite rigid.

Thanks for all the great info in this thread, it was a huge help!

George
Title: Re: My home-made ferrite antennas
Post by: dfroula on June 28, 2014, 09:57:45 AM
Nice job!

I still glue mine too, although I don't think it is needed. I use a clear epoxy. I noticed that the glue introduces a very small gap between the individual ferrite slugs. It is visible if held up to a strong light source.

I think you may actually get more "intimate" contact between the ferrite slugs by not using glue, per Mike's Method of just using the shrink tubing.

I tried a half dozen different industrial glues. The joints made with every one fractured on a 1 inch drop test to the workbench. It's just the nature of the ferrite material.

Don
WD9DMP
Title: ,
Post by: DaleReid on June 28, 2014, 10:40:59 AM
I had the same concern about the gap in between the rods no matter how you applied it, and while not a real circuit in conductive contact rather than having a break the virtual rod with any insulating material, I figured the heat shrink would be enough.

My experience was that I didn't have to waste time (in retrospect) with the futzy and potentially ruining a set by having the glue leak down and adhere to whatever it was holding the rods in alignment, such as a piece of angle aluminum, etc.

The shrink wrap sizes given were perfect, and using a true heat shrink gun (cheap as anything I've gotten lately, from Harbour Freight) made the shrinking fast, fun and nearly foolproof, vs. trying to use my wife's hair drier.

The worst part of winding the rods was the initial piece of wire that had to stick out a foot or two and go round and round while I wound it, but the second one went better when I realized I could roll the extended lead up in a circle and gently tape it to the end of the rod after I got the first inch or two wound on.  And winding for a bit and applying a little bit of Scotch 3M electrical tape to keep it from unwinding if I had to take a break or maybe a sip of something, was helpful.

I used the smaller gauge diameter enamel, too.  One thing that some of the initial stuff from the development team was cautioning that proper spacing between the winds was necessary, even implying that a dummy cord or something to specifically separate the winds a little bit was needed.  I don't see anyone doing home brew doing anything except nestling each rotation up next to the one that was just laid down, forming a relatively solid wind, almost like a hose on a reel or line on a fishing reel.

I don't have a rod from the kit so I can't comment as to how the ones that are sold with the kit are rolled. 

Has anyone taken a look at what Egon, et.al. are sending out?  Are the winds next to one another, or is there some spacing material wound along with it to separate them a bit?

Nonetheless, the proof is in the pudding, and these home built ones, no matter what size wire used, and whether or not glued or just heat shrunk, seem to be spectacular.

Considering the rods are first shrunk, then wound which actually does give a teeny bit of stiffness in its own right, then again heat shrunk, then placed in some sort of support like cotton batting or live rubber or the stuff I used, low density foam rubber strip used as a window door sealer that is adhesive on one side, and then stuffed in PVC means that they'll withstand a 12.7 on the Richter scale and still stretch and yawn and shake it off.

I think the glue is not needed.

I think there are many factors on the size of enamel wire used, including more wraps means more magnetic line crossings as the wave moves by, there are resistance changes, there is the impedance which affects the filter resonance and Q, etc. which I'm sure technically makes a difference.  But again, if the engine starts and runs, who cares if it is 87 octane or 91?

On the other hand, I'm sure if NASA was doing it, they'd test glues vs. no glue, and length of rod and size of wire and spacing of wraps and so on, and find some differences that might make a difference if the probe were going to the heliosphere or a person's life depended upon it.  But if it works and is close to optimal, it probably isn't worth anyone's time doing those experiments.

I have an interest in antennas, so if there are those who know the answers to some of the questions being raised, I'd love to hear the comments.  I love the impetus to learn and look stuff up that this movement has generated.

Dale
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 28, 2014, 11:17:26 AM
Electrically, bonding the rods is not necessary other than if you desire some piece of mind or temporary rigidity... the bonds likely won't hold anyway, unless you can obtain some of the very expensive chemically active epoxy designed expressly for ferrite material.
All that's really necessary for a flux, magnetic, 'connection' is that they be touching with no gap. They then behave as one "longer" ferrite. We'd desire magnetic coupling not capacitive which gaps introduce, and then all them damn Q's and gausses and stuff really get diddled with.
Thinner wire means more turns, more 'sensitivity" and fits inside the 2nd suggested shrink tubing. Thicker, fewer turns, and may not fit. So, get bigger tubing, and have less gain... doesn't matter a lot overall. But we've got a bunch of stations using the 26ga multiple core 50mm X 7.5mm ferrites... and if have any questions about whether Don's innovation, glued or unglued, works, just go check the 'participant's page, and forget all the fancy electrical theory... just follow the cookbook.
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 28, 2014, 11:20:39 AM
The cookbook... remember that if you truly want to make a cake from scratch, first you have to create a "Big Bang" and all that goes with it.

Fortunately for us that's been done already... all we need are ingredients and directions... mess much with either one, and you won't get cake.
Title: Re: ,
Post by: dfroula on June 28, 2014, 11:22:56 AM
The worst part of winding the rods was the initial piece of wire that had to stick out a foot or two and go round and round while I wound it....

Cat toy!
Title: Re: ,
Post by: Jumpin Joe on June 28, 2014, 01:13:52 PM
The worst part of winding the rods was the initial piece of wire that had to stick out a foot or two and go round and round while I wound it....

Cat toy!

You guys should have seen me trying to wrap my 12" ball.... should have videoed it. It was hilarious.  At the time is was... shall I say fustrating?!?!?!? :lol:

Joe
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 28, 2014, 01:51:03 PM
The shrink wrap I used was pretty thick.  I had left some wrap hanging off the end.  I hand drilled a small hole through the wrap at the starting end.  I then strung the wire through the hole and left a good foot out the end.  But that way the hole helped with the first few wraps of wire.  Once I had probably a dozen tight turns around, I used some black tape to hold that.

Once I got a bit further down, I pulled that piece off so the black tape would fully cover the end.  But the whole trick works nicely.  I put a knot at the starting end of my wire so I know which end is which.  But even without the knot, you could see the difference where one wire was more centered than the other.
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 28, 2014, 02:23:14 PM
Electrically, bonding the rods is not necessary other than if you desire some piece of mind or temporary rigidity... the bonds likely won't hold anyway, unless you can obtain some of the very expensive chemically active epoxy designed expressly for ferrite material.
All that's really necessary for a flux, magnetic, 'connection' is that they be touching with no gap. They then behave as one "longer" ferrite. We'd desire magnetic coupling not capacitive which gaps introduce, and then all them damn Q's and gausses and stuff really get diddled with.
Thinner wire means more turns, more 'sensitivity" and fits inside the 2nd suggested shrink tubing. Thicker, fewer turns, and may not fit. So, get bigger tubing, and have less gain... doesn't matter a lot overall. But we've got a bunch of stations using the 26ga multiple core 50mm X 7.5mm ferrites... and if have any questions about whether Don's innovation, glued or unglued, works, just go check the 'participant's page, and forget all the fancy electrical theory... just follow the cookbook.

I agree--in fact, one point in favor of the "heatshrink the cores first" method, aside from helping with rigidity, is that it provides some elastic force holding the cores together.  With high-permeability cores such as these, air gaps can have a significant effect.
Title: Re: My home-made ferrite antennas
Post by: JonathanW on June 28, 2014, 02:54:35 PM
For the curious, here's what my LCR meter says on the two ferrites I rolled...

Ferrite 1:
1 kHz:
1 kHz 10 kHz 100 kHz
Q 27.1 7.08 3.77
Inductance (mH) 20.840 19.562 13.799

Ferrite 2:
1 kHz 10 kHz 100 kHz
Q 26.3 6.27 3.46
Inductance (mH) 22.090 20.590 13.787

Also, my kill-a-watt meter has pegged system power usage, including power lost to the power supply, consistently at 2.5 watts.
Title: Re: My home-made ferrite antennas
Post by: 92merc on June 28, 2014, 02:56:12 PM
When I started making my second set of antennas, I decided to peel one of Egon's covers back to see what he did on the wire at the "done" end and how he brought it back.  I noticed he brought his straight back.  Not winding back like some of the others had done.

It got me to thinking, if that wire wrap on the way back is the opposite winding, could that negate some of the existing windings?  Basically counter effecting what was done?  Its only 10 or so wraps, but still.

So I figured if it's good enough for Egon to go straight back, that's what I did.  Plus I can feel the wire though my black tape and tell which is which, if for some reason I lost a knot and didn't know which end was which.
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 28, 2014, 05:07:57 PM
FYI... Egon doesn't build the antennas ... I cannot recall the name, but the ferrites were originally, possibly still are, built by an associate of the network.

Title: Re: My home-made ferrite antennas
Post by: robo on June 28, 2014, 05:58:58 PM
Wolfgang Friese
http://www.friese-electronic.de/sfericsempfang/komponenten/ferritantennen/

cu Robo :)
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 28, 2014, 08:14:33 PM
Wolfgang Friese
http://www.friese-electronic.de/sfericsempfang/komponenten/ferritantennen/

cu Robo :)
Thanks, Robo... my apologies to Wolfgang... I could not remember that to save my life... ](*,)
Title: Re: My home-made ferrite antennas
Post by: schaffer970 on July 06, 2014, 07:13:23 PM
Just wanted to mention that I was at Harbor Freight yesterday and they are carrying shrink wrap in various diameters by 8 foot long.  Price was only a couple of dollars.  It was in the electrical aisle at my store.  Good price and local for a lot of us.  :-)
Title: Re: My home-made ferrite antennas
Post by: DaleReid on July 06, 2014, 10:57:58 PM
Thanks for the heads up. Maybe not NASA quality, but works OK.

I am headed there tomorrow for a few things, but usually don't have time to browse the aisles to see whats new or what's on sale other than the flier.

Dale

PS, I think one of the most valuable parts of a forum such as this is sharing WHERE they found it and WHAT others are putting into service.  Lots of great ideas. Sometimes there are things in stores (such as the stainless steel bar sink screen at Menards) that someone told all use Rainwise/Davis/Etc tipping bucket users about and it works great for a couple bucks.  I'd never have found it otherwise.

Share and use if you like.

Title: Re: My home-made ferrite antennas
Post by: W3DRM on July 06, 2014, 11:43:05 PM
A word of caution about the HF heat-shrink tubing. I bought a pack from them a while back and discovered there were hard spots in some of the tubing. Of course, the hard spots did not show up until I was in the process of shrinking the tubing. I had to toss away about half of the tubing I got because of this.

I did take the remaining amount back along with a couple sections that were hard and did not shrink. They refunded my cash immediately. I then placed an order for some on eBay and it worked perfectly without any problems at all other than the inherent delay with such orders. It may have been just a bad batch...
Title: Re: My home-made ferrite antennas
Post by: DaleReid on July 07, 2014, 07:16:41 AM
Don,
Very frustrating.

But as I said, not NASA quality.  And I won't put life nor limb in danger with any of their products.  Not that any brand can't fail, but they are at the lower end of the price scale.  I have some items that work great (heat gun, some tools, etc) but others are lower on the scale.

Dale
Title: Re: My home-made ferrite antennas
Post by: dfroula on July 07, 2014, 10:38:54 AM
Their "Earthquake" series of (orange) air tools are of excellent quality. Much of the rest is marginal, though I still happily purchase lots of stuff from them and return it when defective.

I have had wrenches where the chrome plating peels off in wide strips after the first use!

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: JonathanW on July 07, 2014, 08:24:25 PM
I went with this:  http://www.amazon.com/dp/B00843KQQI/ref=pe_385040_30332190_TE_3p_M3T1_ST1_dp_1 (http://www.amazon.com/dp/B00843KQQI/ref=pe_385040_30332190_TE_3p_M3T1_ST1_dp_1)

If you have something else to order through Amazon, it's eligible for free shipping (ships from China, but it's defect free).
Title: Re: My home-made ferrite antennas
Post by: Silversword on July 08, 2014, 02:03:33 PM
Hi All,

I got my heat shrink tubing from eBay at:

 http://www.ebay.com/itm/260920143914?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2FElectrical-Test-Equipment-%2F92074%2Fi.html%3F_from%3DR40%26_nkw%3D260920143914%26_rdc%3D1 (http://www.ebay.com/itm/260920143914?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2FElectrical-Test-Equipment-%2F92074%2Fi.html%3F_from%3DR40%26_nkw%3D260920143914%26_rdc%3D1)

Free shipping. I got 25' for $9.50 total price.

Seems to be good so far.

I ordered more ferrite cores and will try to wind another set without making that winding for the return but a straight line to the other end and see what happens.

My station will probably be down for several days so I can put a shield on the current antenna and move it out side of the house as it is still under my aluminum roof. Need to build a box that might be weather resistant outside wall of the house..

I also need to check my soldering for the OP amps to see if that might solve some of my issues.  They are the SMD's components that I am not sure of.

Hope when I can get this done this Summer that my system will be working better.

Thanks all for your support with this project.

Regards,

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: DaleReid on July 08, 2014, 09:14:30 PM
Stan,
Come mid-winter you'll have a whole bunch of guys volunteering to come help you!

Good luck.

Dale
Title: Re: My home-made ferrite antennas
Post by: W3DRM on July 09, 2014, 11:19:55 AM
+1  :lol:
Title: Re: My home-made ferrite antennas
Post by: Silversword on August 11, 2014, 05:04:06 PM
Hi All,

Since the storm has passed, I can now continue to try to improve my system.

To start, I have decided to make another 300mm ferrite antenna.  I will leave my current one as is.

For the second one, I will shield it with aluminum tape as I cannot find copper foil around here as of yet.  I have plenty of aluminum tape from other construction projects around the house.

I will heat shrink the six ferrite rods without gluing. Then wind them with #26 copper wire. Then put another heat shrink over the windings.

A question as to shield it on the outside of the PVC tubing or shield it over the second heat shrink tubing? If I shield it over the heat shrink, I should be able to put the aluminum foil tape around the wrapped ferrite cores without having to put another strip of foil around the cores.

Is the spacing between the wrapped core and the shield critical?  If I shield it on the heat shrink tubing then the space between the core and the shield will be only a few mm away compared, if the shield is on the out side of the 3/4 PVC tube, the distance will be about 10mm away from the core.

Guess I am just thinking about the Faraday effect??

Any thoughts, suggestions or other ideas?

Regards,

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on August 11, 2014, 05:25:43 PM
Hi Stan... glad you and most folks came through ok....
Well, yeah, there are complicated mathematics about shielding.... but who wants to go there???...especially since I sure don't have the equipment to measure stuff like that....
Remember, the shielding only affects E field signals, so if your interference is magnetic, it will have little effect... having said that, I'd put them in a 1/2 PVC, or even just a paper tube wrapped around them, with the tape on top of that... so if it's removed it'll come off the ferrites with little effort. The longitudinal gap required isn't critical, ... maybe a 16th inch... that is to keep the H field from being shorted out, but will help to take some of the E field to ground without affecting H field reception to a great degree. It will have a very slight effect on H field, however. But that can be minimized if you want to look up all the fancy math and process it. I don't care to! I'd just drop a decimal point or an exponent somewhere and really mess it up. Assuming I could measure all the distances, etc

Mike
Title: Re: My home-made ferrite antennas
Post by: W3DRM on August 11, 2014, 10:25:10 PM
Ditto to what Mike said...

I used 1/2" PVC piping and inserted the ferite rods inside. Then, I used the aluminum tape as a shield. It made a huge difference once I grounded the shields. My noise dropped to almost nothing once I did that yet, I still had great H-field signals. The other thing I did to reduce my noise levels was to install the 5v power supply that Cutty recommended. It brought my noise levels down even further and I have a much cleaner looking 5v line.
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 11, 2014, 11:52:56 PM
Just to nit-pick.... :grin:

The shields don't remove the E-Field component of the lightning signal. An electromagnetic wave (i.e. radio signal) must have both an E and H in-phase component to exist! You can't filter out one from the other!

Distinct from EM radio waves are near-field E or H fields that are out of phase with each other, but still generated together by an electric current. You can filter out near E-field interference, as it is capacitively coupled into an antenna. Inductively-coupled magnetic near field signals can't be shielded without also filtering the desired EM signal.

The foil shielding gap allows the E and H EM wave components to flow on the inside of the shield, where they are coupled to the antenna coil. Electrostatic near-field interference is drained to ground. Near field magnetic interference is unaffected by the shield.

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: Silversword on August 19, 2014, 04:03:22 PM
Hi All,

I had some chance to work on my second set of ferrite antennas. This time it is in 1/2 in. PVC and I have it shielded with aluminum foil that I had on hand.  I could do the foil wrapping with one wrap as the width of the foil was 72mm or 2.83 in. Had to cut the length so to have about 1/8 in gap.  Now have to get it installed into the 90 enclosure with the barrier strip inside. The foil will be grounded, at least I hope so.

I also did the power supply, as Don (W3DRM), suggested.  I see that the 5 v has less hash compared to what I was using.

I still have to check on the soldering for the OP amps on the amplifier board.  Just to double check on it.  Hope I find some pins that might be an issue to improve the amplifier board efficiency.

Now a question, I am using shielded audio cable that will run between the antenna and the amplifier board. How long can the cable be?  Probably short as possible, but I would like to have the antenna outside and the amplifier inside if possible. I have a place outside for the antenna that is about 10 feet to where I could place the amplifier board bud enclosure.

Still trying to minimize interferences.  The current unshielded ferrite antenna is inside my house under a aluminum roof.  Like to get it outside to see what happens with a shielded antenna.

Any recommendations will be appreciated.

Regards,

--Stan Y.
   Maui, Hawaii




 
Title: Re: My home-made ferrite antennas
Post by: JonathanW on August 19, 2014, 04:13:59 PM
Hi All,

I had some chance to work on my second set of ferrite antennas. This time it is in 1/2 in. PVC and I have it shielded with aluminum foil that I had on hand.  I could do the foil wrapping with one wrap as the width of the foil was 72mm or 2.83 in. Had to cut the length so to have about 1/8 in gap.  Now have to get it installed into the 90 enclosure with the barrier strip inside. The foil will be grounded, at least I hope so.

I also did the power supply, as Don (W3DRM), suggested.  I see that the 5 v has less hash compared to what I was using.

I still have to check on the soldering for the OP amps on the amplifier board.  Just to double check on it.  Hope I find some pins that might be an issue to improve the amplifier board efficiency.

Now a question, I am using shielded audio cable that will run between the antenna and the amplifier board. How long can the cable be?  Probably short as possible, but I would like to have the antenna outside and the amplifier inside if possible. I have a place outside for the antenna that is about 10 feet to where I could place the amplifier board bud enclosure.

Still trying to minimize interferences.  The current unshielded ferrite antenna is inside my house under a aluminum roof.  Like to get it outside to see what happens with a shielded antenna.

Any recommendations will be appreciated.

Regards,

--Stan Y.
   Maui, Hawaii


That's a good question -- I've seen several admonitions regarding capacitance in the leads between the ferrites and the H-field amplifier.  This may or may not be an issue with audio cable (my guess is it would, though the input resistor lowers the Q quite a bit in any case).

For my own setup, I installed the H-field amplifier right at the ferrites, and the cable to the controller is the longer one (cat5e shielded).

Best,
Jonathan
Title: Re: My home-made ferrite antennas
Post by: W3DRM on August 20, 2014, 10:42:45 AM
Hi All,

I had some chance to work on my second set of ferrite antennas. This time it is in 1/2 in. PVC and I have it shielded with aluminum foil that I had on hand.  I could do the foil wrapping with one wrap as the width of the foil was 72mm or 2.83 in. Had to cut the length so to have about 1/8 in gap.  Now have to get it installed into the 90 enclosure with the barrier strip inside. The foil will be grounded, at least I hope so.

I also did the power supply, as Don (W3DRM), suggested.  I see that the 5 v has less hash compared to what I was using.

I still have to check on the soldering for the OP amps on the amplifier board.  Just to double check on it.  Hope I find some pins that might be an issue to improve the amplifier board efficiency.

Now a question, I am using shielded audio cable that will run between the antenna and the amplifier board. How long can the cable be?  Probably short as possible, but I would like to have the antenna outside and the amplifier inside if possible. I have a place outside for the antenna that is about 10 feet to where I could place the amplifier board bud enclosure.

Still trying to minimize interferences.  The current unshielded ferrite antenna is inside my house under a aluminum roof.  Like to get it outside to see what happens with a shielded antenna.

Any recommendations will be appreciated.

Regards,

--Stan Y.
   Maui, Hawaii

Stan, the leads from the antenna (ferrite or loop) must be as short as possible. It is my understanding that the H-field amp must be in close proximity to the antenna. Adding any distance introduces delays and signal charateristic changes that are not wanted in this system. In my case, I built an enclosure for both my H-field and E-field antennas that is located about 35 to 40 feet from my house. The H amp also sits in that enclosure and is connected to the controller board via a 50-foot shielded TWP Cat-6 Ethernet cable. Moving my antennas out of my house resulted in a huge decrease in noise levels. I suspect you will find the same thing when/if you move yours out from under your metal roof.
Title: Re: My home-made ferrite antennas
Post by: miraculon on August 20, 2014, 11:00:30 AM
Quote
Now a question, I am using shielded audio cable that will run between the antenna and the amplifier board.

I think that the recommendation has always been to minimize the length. Also, are you sure that you want to use audio cable? Some audio cables are pretty high capacitance. I realize that we are dealing with low Z and low frequencies, but you might want to at least find out what your pF per foot of that cable is.

Greg H.


Title: Re: My home-made ferrite antennas
Post by: W3DRM on August 20, 2014, 11:05:33 AM
Stan, if you haven't already done so, you might want to post your question on the BO forum itself. That way, the developers will see it and can respond directly. I think adding any length of cabling is going to alter the circuit parameters and would not be an acceptable means of building a RED system.
Title: Re: My home-made ferrite antennas
Post by: Silversword on August 24, 2014, 04:43:34 PM
Hi All,

Got to work on the system.

Made a second set of 300mm ferrite antenna.  Enclosed it with 1/2" PVC.  Shielded it with aluminum tape foil. Used shielded two wire audio cable about a foot long.  The first one was about 4 feet long... The shield is grounded through the grounding on the amplifier board connector strip..Also when I wound the core, for the return wire, instead of back winding it a few turns, I just ran it a straight line to the start side.  This wire is being grounded as well as the shield through the amplifier board.

Re-soldered the OP amps on the amplifier board. Some of the solder pad looked kinda flacky under a low power microscope.  All 64 pads looks good now.

Antenna is still in the house.  Next step is to build an enclosure for the antenna to be outside somewhere and be protected from our wet environment.

I have no idea if all this so far has made any improvements with my interference.. 

Anyone could check it out for me?

Hope that the move outside will make a significant change when that happens.

Will keep you all posted.

Any comment or suggestions welcome.

Regards,

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on August 24, 2014, 05:47:09 PM
I don't know, Stan... you can view your signals at http://frankfortweather.us/BoStaSig/maui993/index.html
snapshot attached...

Mike


Title: Re: My home-made ferrite antennas
Post by: Silversword on August 24, 2014, 07:06:27 PM
Thanks Mike for your input.  Don't know what it means either.  Here is another snap shot just a little while ago.

Don't know how to interpret this one too.

Regards,

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on August 24, 2014, 07:26:11 PM
Thanks Mike for your input.  Don't know what it means either.  Here is another snap shot just a little while ago.

Don't know how to interpret this one too.

Regards,

--Stan Y.
   Maui, Hawaii

That looks like as set of skywave signals from a stroke,   Of more concern would be the interference spikes periodically around 21-24, 43-46, and 69-70...
betcha the culprit is Navy VLF transmitter near Lualualei  at 21.4 kHz and 23.4 kHz, and a bunch of megawatts. They're talking to submarines... .
Title: Re: My home-made ferrite antennas
Post by: JonathanW on August 24, 2014, 07:28:33 PM
On the one hand, the interfering signals are really only showing up on the FFT when it's at its lowest range (+/- 91 mV full scale)-- at what looks like 22, 42, and 68 kHz (about).  On the other, when you're trying for long range specifically due to lack of additional local stations around you, anything's going to be problematic. 

Interesting signals - wonder if it's sub communications?  The consistent 24 kHz signal we see in the east is likely due to the 2 MW sub communications transmitter in Maine.

EDIT: I see Mike beat me to it :)
Title: Re: My home-made ferrite antennas
Post by: Silversword on August 24, 2014, 07:57:32 PM
If it is some VLF signals for under water communications, they are still wrapping up the recent RIMPAC operations from last month. Should have been completed the first week in August.

Will see what happens when I can get the antenna out side in an enclosure.  Maybe next weekends project.

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: W3DRM on August 24, 2014, 11:41:46 PM
If it is some VLF signals for under water communications, they are still wrapping up the recent RIMPAC operations from last month. Should have been completed the first week in August.

Will see what happens when I can get the antenna out side in an enclosure.  Maybe next weekends project.

--Stan Y.
   Maui, Hawaii

Due to their nature, submarine VLF comms run at an extremely low baud rate. They transmit continuously and it takes hours or more just to transmit a single message. From what I have read, they operate 24/7 so, if it really is these comms causing the interference, they will never go away. It they stop, then most likely you are getting interference from something else.
Title: Re: My home-made ferrite antennas
Post by: Silversword on September 09, 2014, 04:26:25 PM
Hi All,

Update on my antenna placement.

Finally found the time to get it on the roof and above the metal of the roof.

Hope it will work out better at this location.  The metal roof is just under the enclosure.

The top cover seal is from ACE Hardware for camper top seal.

Now the antenna is more in open air and hope less interference...

Any comments welcome for this install.

See attachment.

Regards,

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: W3DRM on September 10, 2014, 12:49:55 PM
Nice installation Stan. Is the antenna horizontal? I can't tell by the photo.
Title: Re: My home-made ferrite antennas
Post by: Silversword on September 10, 2014, 03:32:35 PM
Nice installation Stan. Is the antenna horizontal? I can't tell by the photo.

Hi,

Thanks Don for the comment.  Took a while to make the box and some what weather resistant.  Made from 3/4" marine ply that I had left over from another project.  Painted with Deck Over by Behr from Home Depot...Another left over from that same other project...  It is kinda heavy and really not secured to the roof but just laying on top.  Put a cinder block tile on top for more weight.  Will see how it holds up... It is 24" X 24" X 8" for the foot print...

The box is sitting on the roof so the antenna is horizontal and the ends are perpendicular to the power lines that kinda goes to both side of our place..

The photo is kinda looking down into the box...

--Stan Y.
   Maui, Hawaii
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on May 23, 2015, 10:29:01 AM
 :twisted: This topic needs to be bumped.  Especially with the new "Blue" system on the horizon... So, here... "BUMP", dang it...
Title: Re: My home-made ferrite antennas
Post by: orion_jb2001 on August 10, 2015, 05:37:26 AM
Hey all,

interesting constructions.  What type of wire are you using from the winding wire to the actual amp. By the look of it, you don't have the winding wires going to the amp, so the wire these connect to, do they have to be shielded, specific type of wire....  ???


Jeff
Title: Re: My home-made ferrite antennas
Post by: miraculon on August 10, 2015, 08:20:27 AM
Hey all,

interesting constructions.  What type of wire are you using from the winding wire to the actual amp. By the look of it, you don't have the winding wires going to the amp, so the wire these connect to, do they have to be shielded, specific type of wire....  ???


Jeff

I can't speak for this particular antenna since I don't have one, but the "magnet" wire is too small to be captured reliably by the screw terminals on the amplifier input. Normally, the magnet (coil) wire is soldered to a larger stranded section that is OK for the screw terminals. The solder joint is protected by shrink wrap.

Some magnet wire requires sanding or stripping to remove the insulation varnish (or poly), other types will solder-strip. Be careful not to nick the wire or it might break.

Greg H.
Title: Re: My home-made ferrite antennas
Post by: orion_jb2001 on August 10, 2015, 08:50:02 AM
Thanks Greg.  I am aware of the problems with the magnet wire and the terminals.  What I am trying to confirm, will any wire do for this "link" from the magnet wire to the board or should it be a particular type of wire?

regards,

Jeff
Title: Re: My home-made ferrite antennas
Post by: miraculon on August 10, 2015, 09:00:44 AM
Thanks Greg.  I am aware of the problems with the magnet wire and the terminals.  What I am trying to confirm, will any wire do for this "link" from the magnet wire to the board or should it be a particular type of wire?

regards,

Jeff

I just used some common 24AWG or so stranded "hookup" wire. On the original Blitzortung ferrite antennas, there was a knot on the "start" winding. I used a different color wire so I know which one it is after all the shrink wrap goes on.

The instructions from the developers say to not twist these two wires since it will increase capacitance. There may be some rejection benefit from twisting the signal pair and the capacitance effect has got to be very small at our frequencies. I have a gentle twist rate on mine as a compromise (about 1-2 twists per inch).


Greg H.
Title: Re: My home-made ferrite antennas
Post by: dfroula on August 10, 2015, 02:47:03 PM
Hey all,

interesting constructions.  What type of wire are you using from the winding wire to the actual amp. By the look of it, you don't have the winding wires going to the amp, so the wire these connect to, do they have to be shielded, specific type of wire....  ???


Jeff

I think you're referring to my station, as I first put these antenna's together. I used short lengths of shielded two-conductor microphone cable. The shield and ground wire of the cable are tied together and to the shielded tube and one end of the antenna on the antenna end.

On the other end, the shield and ground are tied together and connected to the ground terminal of the amp channel.

The red wire goes to the other antenna wire and the amp "hot" connection at the amplifier.

That said, I think the shielded cable is completely unnecessary. It is more for mechanical strength. Just solder the free ends of the antenna to a larger diameter piece of copper wire so the terminals of the amplifier and grip it properly.

Best,

Don
WD9DMP
Title: Re: My home-made ferrite antennas
Post by: bobbinnd on September 03, 2017, 10:22:32 AM
Don,

I am just starting out with a new System Blue, and have been reading EVERYTHING I can find about antenna's and mounting them. I live, live in North Dakota, so the weather can be brutal due to wind, ice and snow, and I am trying to figure out the best way to mount everything outside. I bought 3 ferrite cores from Egon, as I knew this would likely be a one time shot at this, so I think I will try your idea of the "L" PVC but with the 3rd core going vertical. 

Do you still use you antenna's seen on the string, or have you modified them and am have missed that information somehow?

As I said, I live in North Dakota, and the Navy has a very large VLF tower about 19 miles away, it happens to be where I work. I image that I will have to deal with this issue as well, but won't be able to figure that out until after I get the System up and running.

Thanks for a very informative explanation of what you built. Can I mount the E-Field in the same container as the H-field probes?
Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on September 03, 2017, 11:21:19 AM
I would mount them separately... with the E field as far from obstacles, structures etc as is feasible... and at least 2-3 meters above ground or metal.... It's best to find a location, for antennas before 'permanently' designing an enclosure, in my opinion.  I'd hold off on the vertical H field until I determined H field environment fairly clean... in my case the 'vertical' H environment is incredibly noisy.
NML lists at 25.20 kHz which will be a pain in the antenna for you.... we're really concerned in the 3K to 30K bandwidth! might have to go 2 antennas at 90 and axial one directly at the transmitter... maybe install filter IC on that channel and cutoff off about 22kHz... I read that there was talk of converting that facility to 150 kHz in which case your could obtain more hi frequ with a cutoff set about 130... You are close, and it may be very irrating, as the ground wave component will be very strong.... good luc... Shouldn't bother E field as much
Title: Re: My home-made ferrite antennas -- Alternative Ferrite?
Post by: Jim-Bob on May 31, 2018, 08:50:45 AM
Hello all
1st post here.
A quick search reveals
https://www.fair-rite.com/product/antennarfid-rods-3078990891/ (https://www.fair-rite.com/product/antennarfid-rods-3078990891/)
Which is available at
https://uk.rs-online.com/web/p/ferrite-rods/4674059/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E285C647B362C377D5B4161426250705D297C285C647B337D5B5C732D2F255C2E2C5D5C647B332C347D5B4161426250705D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3436372D34303539267374613D3436373430353926 (https://uk.rs-online.com/web/p/ferrite-rods/4674059/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E285C647B362C377D5B4161426250705D297C285C647B337D5B5C732D2F255C2E2C5D5C647B332C347D5B4161426250705D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3436372D34303539267374613D3436373430353926)

and many other RS component locations.

Is this close enough?

Part Number: 3078990891
78 ROD
Medium Permeability, 78 (ui=2300) material

Title: Re: My home-made ferrite antennas
Post by: schaffer970 on May 31, 2018, 11:08:46 AM
Hello all
1st post here.
A quick search reveals
https://www.fair-rite.com/product/antennarfid-rods-3078990891/ (https://www.fair-rite.com/product/antennarfid-rods-3078990891/)
Which is available at
https://uk.rs-online.com/web/p/ferrite-rods/4674059/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E285C647B362C377D5B4161426250705D297C285C647B337D5B5C732D2F255C2E2C5D5C647B332C347D5B4161426250705D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3436372D34303539267374613D3436373430353926 (https://uk.rs-online.com/web/p/ferrite-rods/4674059/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E285C647B362C377D5B4161426250705D297C285C647B337D5B5C732D2F255C2E2C5D5C647B332C347D5B4161426250705D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3436372D34303539267374613D3436373430353926)

and many other RS component locations.

Is this close enough?

Part Number: 3078990891
78 ROD
Medium Permeability, 78 (ui=2300) material
I would mount them separately... with the E field as far from obstacles, structures etc as is feasible... and at least 2-3 meters above ground or metal.... It's best to find a location, for antennas before 'permanently' designing an enclosure, in my opinion.  I'd hold off on the vertical H field until I determined H field environment fairly clean... in my case the 'vertical' H environment is incredibly noisy.
NML lists at 25.20 kHz which will be a pain in the antenna for you.... we're really concerned in the 3K to 30K bandwidth! might have to go 2 antennas at 90 and axial one directly at the transmitter... maybe install filter IC on that channel and cutoff off about 22kHz... I read that there was talk of converting that facility to 150 kHz in which case your could obtain more hi frequ with a cutoff set about 130... You are close, and it may be very irrating, as the ground wave component will be very strong.... good luc... Shouldn't bother E field as much
See 3w3.we 3 33333

Sent from my SM-N950U using Tapatalk

Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on May 31, 2018, 12:07:40 PM
The Antennas in this thread topic' were all built with 50mm X 7.5 mm rods from
https://www.surplussales.com/Inductors/FerRods/FerRods.html (https://www.surplussales.com/Inductors/FerRods/FerRods.html)
item ICH) ROD7.5/50  ...

Phillips ferrite rod. Soft 3C80 ferrite material great for EMI suppression or tuned coils. EMI suppression DC-200 Mc. RF tuned coils DC-30 Mc. Initial Perm: 2000 20%. Saturation flux density: 500 mT. Residual flux density: 210 mT. Mfg. P/N: ROD7.5/50-3C80. 3C80 has been replaced by 3C90.  Here is a cross referenced specification on 3C80.  3C80 is equivalent to Cosmos Ferrite CF196 material.(https://photos.smugmug.com/Weather/Antennas-Experimental/i-PPf4dnZ/0/9c36db2d/L/DSC03279-L.jpg) (https://www.ourspecialnet.com/Weather/Antennas-Experimental/i-PPf4dnZ/A)(https://photos.smugmug.com/Weather/TwinHollies/i-QtLxk87/0/971b7dd7/S/Blitzortung%20Wall-S.jpg) (https://www.ourspecialnet.com/Weather/TwinHollies/i-QtLxk87/A)
Title: Re: My home-made ferrite antennas
Post by: Jim-Bob on May 31, 2018, 02:04:58 PM
Thank you Cutty Sark Sailor
I have inquired about shipping to the UK from Surplus sales, but have not received a reply.
I'm rather wary about ordering them and not knowing the shipping cost until after they have been sent.
This is why I'm looking for an alternative supplier.
Title: Re: My home-made ferrite antennas
Post by: W0BTU on June 11, 2018, 06:59:20 PM
Do you think that there is any difference in the way these work compared to the antennas that can be ordered from Egon?

Or maybe I should ask if these are the ones you use on your System Blue?  :grin:

The Antennas in this thread topic' were all built with 50mm X 7.5 mm rods from
https://www.surplussales.com/Inductors/FerRods/FerRods.html (https://www.surplussales.com/Inductors/FerRods/FerRods.html)
item ICH) ROD7.5/50  ...

Phillips ferrite rod. Soft 3C80 ferrite material great for EMI suppression or tuned coils. EMI suppression DC-200 Mc. RF tuned coils DC-30 Mc. Initial Perm: 2000 20%. Saturation flux density: 500 mT. Residual flux density: 210 mT. Mfg. P/N: ROD7.5/50-3C80. 3C80 has been replaced by 3C90.  Here is a cross referenced specification on 3C80.  3C80 is equivalent to Cosmos Ferrite CF196 material.

Title: Re: My home-made ferrite antennas
Post by: Cutty Sark Sailor on June 11, 2018, 07:55:00 PM
Do you think that there is any difference in the way these work compared to the antennas that can be ordered from Egon?

Or maybe I should ask if these are the ones you use on your System Blue?  :grin:

The Antennas in this thread topic' were all built with 50mm X 7.5 mm rods from
https://www.surplussales.com/Inductors/FerRods/FerRods.html (https://www.surplussales.com/Inductors/FerRods/FerRods.html)
item ICH) ROD7.5/50  ...

Phillips ferrite rod. Soft 3C80 ferrite material great for EMI suppression or tuned coils. EMI suppression DC-200 Mc. RF tuned coils DC-30 Mc. Initial Perm: 2000 20%. Saturation flux density: 500 mT. Residual flux density: 210 mT. Mfg. P/N: ROD7.5/50-3C80. 3C80 has been replaced by 3C90.  Here is a cross referenced specification on 3C80.  3C80 is equivalent to Cosmos Ferrite CF196 material.


This construction is exactly what I use on all my stations...  I have a pair of 120mm Wolfgang Friese builds which I ordered with my first red years ago... the performance is similar, but the 120mm, being smaller, didn't produce a large enough S/N ratio for my environment...
My blue 1439 runs Delta 250 x 7.5mm modified build, Red 689 runs 300 x 7.5mm modified build... currently the experimental 791 red  has 300mm unmodified build.. the signal image above: Green is a modified ("CSS THINGIE"   http://frankfortweather.us/blitzblitz/CSS%20Thingie.pdf   49MB) build, and red is an unmodified...
Title: Re: My home-made ferrite antennas
Post by: W0BTU on June 15, 2018, 07:27:00 PM
Very well! I plan on getting some of those. After I catch up with paying work here.

I'm in the process of moving my E-field antenna probe from that noisy location on the upstairs balcony to near the H-field antennas. Someday... :grin: