Author Topic: My home-made ferrite antennas (Read 134753 times)

Cutty Sark Sailor · « **Reply #75 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.

dfroula · « **Reply #76 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

Quote from: 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

W7DRM (old call was W3DRM) · « **Reply #77 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.

Silversword · « **Reply #78 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

Cutty Sark Sailor · « **Reply #79 on:** April 17, 2014, 07:23:15 PM »

Quote from: 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

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.

DaleReid · « **Reply #80 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?

W7DRM (old call was W3DRM) · « **Reply #81 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.

Cutty Sark Sailor · « **Reply #82 on:** April 18, 2014, 05:56:56 AM »

Quote from: DaleReid on April 18, 2014, 12:03:04 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

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.

dfroula · « **Reply #83 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

Quote from: 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.

Dr Obbins · « **Reply #84 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.

dfroula · « **Reply #85 on:** April 19, 2014, 07:35:14 PM »

Dave, it looks like your noise issues are under control. Your station stats look great.

Don

Dr Obbins · « **Reply #86 on:** April 19, 2014, 08:09:16 PM »

I am sure good craftsmanship may have had something to do with it also.

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.

Silversword · « **Reply #87 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

DaleReid · « **Reply #88 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.

Silversword · « **Reply #89 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

W7DRM (old call was W3DRM) · « **Reply #90 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.

dfroula · « **Reply #91 on:** April 21, 2014, 03:36:25 PM »

Nice job!

I really like the winding jig idea.

Don
WD9DMP

W7DRM (old call was W3DRM) · « **Reply #92 on:** April 21, 2014, 03:56:10 PM »

Quote from: dfroula on April 21, 2014, 03:36:25 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.

Silversword · « **Reply #93 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

W7DRM (old call was W3DRM) · « **Reply #94 on:** April 21, 2014, 04:51:34 PM »

Quote from: 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

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.

dfroula · « **Reply #95 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

Silversword · « **Reply #96 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

Cutty Sark Sailor · « **Reply #97 on:** May 05, 2014, 06:42:56 PM »

Quote from: 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

Go, Stan, Go! good job!

W7DRM (old call was W3DRM) · « **Reply #98 on:** May 06, 2014, 04:19:58 PM »

Quote from: 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

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):

Signals: 3049
Effectivity S: 0% 4
Effectivity M: 100% 37
Effectivity L: 24%

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.

DaleReid · « **Reply #99 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.

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Author Topic: My home-made ferrite antennas (Read 134753 times)