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New to HF and looking at antenna options.

graywoulf

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Here is one of the best prices I've seen on the FT-240-31 ferrite core at $6 each. Every year at Dayton I stop by Howard's table and get about $200 in ferrite products. Fair-Rite 2.4″ Toroid Core - Pro Audio Engineering

If your going to roll your own make two and put the second one at the radio end. You can sometimes lower the noise level into your receiver doing this.
Thanks for the link to these at that great price. I did order two of them.
 

graywoulf

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Well, the ferrite cores arrived and I have the one that sits near the ladder line done... I guess. So, here is a picture of what I put together and I would like to know if I did this right. This picture only shows the balun attached to the connector board. The ladder line will be attached to the brass terminals and secured to the top of the board. I did nine turns as was instructed and the coax end will be attached to the bottom right corner of the board to direct it downward. I will also add more support to the balun as well. I will also be making one for the radio as well.

So, how did I do?
 

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W5lz

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Could it make a difference? Sure, but no idea how beneficial it would be, if any.
 

prcguy

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Looks great and it should be very effective. As for crossing over half way through the turns, I have not measured the benefits myself but its said it improves things a little by isolating the input and output better. It also puts the input and output on opposing sides of the core making it a better fit for a straight line coax run.

Well, the ferrite cores arrived and I have the one that sits near the ladder line done... I guess. So, here is a picture of what I put together and I would like to know if I did this right. This picture only shows the balun attached to the connector board. The ladder line will be attached to the brass terminals and secured to the top of the board. I did nine turns as was instructed and the coax end will be attached to the bottom right corner of the board to direct it downward. I will also add more support to the balun as well. I will also be making one for the radio as well.

So, how did I do?
 

graywoulf

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Looks great and it should be very effective. As for crossing over half way through the turns, I have not measured the benefits myself but its said it improves things a little by isolating the input and output better. It also puts the input and output on opposing sides of the core making it a better fit for a straight line coax run.
Thank you for that helpful information. I was thinking it would be easier to keep the coax in a straight line opposed to putting a U bend in it.

If I learned anything else this week about antenna building, it is to not use too much coax tape. Man, is that stuff messy to remove when it it warm outside. I ended up having to use charcoal lighter fluid to remove it all and doing that was a huge mess in itself. Next time, I am going to soak it in ice water first or maybe just use silicone sealant instead. It comes off clean with vinegar. I don't expect that hot glue would hold up or I would use that.
 

graywoulf

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Could it make a difference? Sure, but no idea how beneficial it would be, if any.
Well as prcguy pointed out, keeping the coax in line seems to be the best benefit. There is so much I still have to learn. Field day coming up and I plan on being there and taking notes.
 

W5lz

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If I'm understanding correctly, that "in line" thingy is a mechanical consideration. Meaning repositioning the present torroid's position could probably alleviate the 'problem'. Or, simply use another zip-tie to position the coax to come off the bottom of the thing. Electrically I don't think it amounts to much of a problem.
 

graywoulf

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If I'm understanding correctly, that "in line" thingy is a mechanical consideration. Meaning repositioning the present torroid's position could probably alleviate the 'problem'. Or, simply use another zip-tie to position the coax to come off the bottom of the thing. Electrically I don't think it amounts to much of a problem.
The best way that I can explain what I have learned to to direct you to this site and tell you to scroll down to example "D". I do not think that the efficiency is going to be changed either way. It is just that it is easier to keep the coax in a straight line in my application.
 

prcguy

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There are potential electrical reasons to cross over the turns half way through. If you consider some reasons for using a choke balun is to strip off interference riding on the shield of the coax (common mode), then if the input and output of the choke are right next to each other the coupling between them is greater than if the input and output are on opposing sides.

The best way that I can explain what I have learned to to direct you to this site and tell you to scroll down to example "D". I do not think that the efficiency is going to be changed either way. It is just that it is easier to keep the coax in a straight line in my application.
 

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OK, back to learning mode. I understand what you are saying up to "then if the input and output of the choke are right next to each other the coupling between them is greater than if the input and output are on opposing sides". So, are you saying that using the crossover is not going to work? Here is what I just changed.
 

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prcguy

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Looks like you might have crossed over wrong. The crossover will go through the center of the ferrite ring and not just straight across the same side. Here is an example of a proper cross over. This type of winding is supposed to provide better isolation than the same number of turns without a cross over.

loop-choke.jpg


OK, back to learning mode. I understand what you are saying up to "then if the input and output of the choke are right next to each other the coupling between them is greater than if the input and output are on opposing sides". So, are you saying that using the crossover is not going to work? Here is what I just changed.
 

graywoulf

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I wondered about that. Thanks for the picture. I still need nine turns though right? If so, does it matter how many I make before the crossover? Thanks.
 

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Nine turns is still a good middle of the road number for 80 through 10m. If you will never operate 10m on this antenna make it 10 turns. Every time the cable passes through the center counts as one turn and the cross over is one turn. I would try to center the cross over like four turns before, four after and the crossover makes it nine.

I wondered about that. Thanks for the picture. I still need nine turns though right? If so, does it matter how many I make before the crossover? Thanks.
 

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Well, here is version 3. I am glad I don't make these for a living. Having carpal tunnel syndrome doesn't make winding the coax and trying to keep it snug around the core an easy task for me. But I got it done... I hope. :)
 

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prcguy

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That will work. I hope there is no flexing near the lugs as you soldered the braid into a solid mass. Maybe you can Ty-wrap the core to the fiberglass sheet?

Nine turns is still a good middle of the road number for 80 through 10m. Every time the cable passes through the center counts as one turn and the cross over is one turn. I would try to center the cross over like four turns before, four after and the crossover makes it nine.
Well, here is version 3. I am glad I don't make these for a living. Having carpal tunnel syndrome doesn't make winding the coax and trying to keep it snug around the core an easy task for me. But I got it done... I hope. :)
 

graywoulf

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That will work. I hope there is no flexing near the lugs as you soldered the braid into a solid mass. Maybe you can Ty-wrap the core to the fiberglass sheet?
Thanks for all of your help with this. I did in fact use two Ty-wraps to secure the core to the board which is actually nylon. I will seal the open end of the coax with silicone sealant and wrap it all with electrical tape afterwards. With the upcoming field day this Saturday, I plan to take the antenna as well as my 570D and antenna tuner to the event in hopes that it can be set up and tried out. Then if there are any other changes or tuning to be done, I will have help for that. Thanks again.
 

graywoulf

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If your going to roll your own, make two and put the second one at the radio end. You can sometimes lower the noise level into your receiver doing this.
Since I did buy two cores, I want to make the second choke to go to the radio. I will be making a short coupler since I have a pass through panel in a nearby window. Does this choke need to be close to the radio? Thanks!
 

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I put mine in the antenna line close to the radio, tuner or amplifier. If your coax passes by computer cables or noisy equipment on the way outside, it might be better to place the second choke in the line on the antenna side of the computer cables instead of the radio side. A spectrum display is useful to see noise and birdies to find the most effective place to put a choke.

Since I did buy two cores, I want to make the second choke to go to the radio. I will be making a short coupler since I have a pass through panel in a nearby window. Does this choke need to be close to the radio? Thanks!
 
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