Build Simple Effective Common Mode Choke For Antennas.

 If you're bothered by RFI in your ham shack, you may want to build this easy common mode choke for your antenna systems.

In this video, Steve Ellington (N4LQ) takes us step by step through the design, construction, and testing of this useful antenna accessory.

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Here are a few comments from Steve (N4LQ):

These chokes are as good or better than most anything on the market and much cheaper! Most commercial units use tiny ferrite sleeves or beads crammed into a PVC pipe. These have higher impedance and can handle outdoor use. Fair-Rite part number 2631803802 For RG8x or RG8M keep power under 500 watts. This assumes a 1:1 SWR. For higher power or high SWR use RG-400 coax. See link: If you use RG-400 you will have room to slide a piece of 3/4" or 1/2" PVC tubing through the center to devise a means of support however the core / coax assembly is fairly strong anyway. You can put 2, 3 or 4 of these in series for an insane total of choking resistance. Just leave 6" or so between them and use a longer section of coax. If you want a minimum of connectors just use one long coax from the shack to the antenna and wrap a few of these along the path! Use the same cores for AC cords, DC, cords, Speaker cable, Mic. cable, rotator cable ....You name it. BTW: Don't waste your time on a so called "ugly balun" or coax just wrapped around a pvc pipe. They have almost zero inductance! If one actually seems to work it's probably because you added coax length and move the radiation to another spot :*) Good Read RFI and Choke building Have fun building 73 N4LQ

Steve Ellington N4LQ

Thanks for joining us today.

Aloha es 73 de Russ (KH6JRM).


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