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Windom antenna. How to design the choke.

Feb 14th, 15:40

N1AUP

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I built an 80 meter Windom antenna following these instructions.

http://www.hamuniverse.com/k4iwlnewwindom.html

As I understand things, I have to build a choke to keep RF off of the coax feedline. I bought 1 foot worth of ferrite cylinders, and am going to put them on a piece of RG8X cable.

The plans suggest that I need ten feet of coax between the antenna balun and the beginning of the choke. I've also read that you don't need the 10 foot section.

Does this antenna need a choke? What distance from the antenna feed point does the choke have to start? Is 10 feet the right length? I think the 8x that I bought at HRO has a foam dielectric.

Thanks
N1AUP
Feb 14th, 20:39

N5CM_John

Joined: Sep 6th 2017, 16:13
Total Topics: 0
Total Posts: 0
In the 23rd edition of the ARRL Antenna Book on page 10-7, there is a reference to the "Carolina Windom", which sounds like what you built. For their 80m antenna, they used a 22-foot section of coax below the feed point balun and inserted a 1:1 choke at that point. The feedpoint balun was a 4:1 voltage balun which, per the Antenna Book, does not act like a current choke. So, the 22-foot section of RG8X between the 4:1 voltage balun at the feed point and the 1:1 choke 22 feet down, radiates and fills in nulls. I have an old Carolina Windom (10m-40m) that I resurrected in Februaru 2018 after my 10+ years QRT. It is my only "store bought" antenna and it works fairly well. I use it with a tuner in the shack on all bands, 10m through 40m. I've worked a lot of states and DX with that antenna on CW. I would think the 1:1 choke down on feed line would be a good idea.

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