Topic: My home-made ferrite antennas

[Cutty Sark Sailor]

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.

[robo]

Wolfgang Friese
http://www.friese-electronic.de/sfericsempfang/komponenten/ferritantennen/

cu Robo

[Cutty Sark Sailor]

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...

[schaffer970]

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. 

[DaleReid]

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.

[W7DRM (old call was W3DRM)]

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...

[DaleReid]

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

[dfroula]

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

[JonathanW]

I went with this:  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).

[Silversword]

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

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

[DaleReid]

Stan,
Come mid-winter you'll have a whole bunch of guys volunteering to come help you!

Good luck.

Dale

[W7DRM (old call was W3DRM)]

+1 

[Silversword]

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

[Cutty Sark Sailor]

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

[W7DRM (old call was W3DRM)]

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.

[dfroula]

Just to nit-pick....

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

[Silversword]

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




 

[JonathanW]

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

[W7DRM (old call was W3DRM)]

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.

[miraculon]

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.

[W7DRM (old call was W3DRM)]

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.

[Silversword]

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

[Cutty Sark Sailor]

I don't know, Stan... you can view your signals at http://frankfortweather.us/BoStaSig/maui993/index.html
snapshot attached...

Mike

[Silversword]

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

[Cutty Sark Sailor]

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... .