Building an all-band HF Air Choke

Having recently installed an end-fed 10m long wire antenna, the problem I was facing was feedline radiation, or RF into the shack. I knew this was happening because a touch-operated desk lamp would come on and off and I transmitted, which was most annoying.

I needed to build a 1:1 choke balun. So I did a quick search on the internet an arrived at the page of K8DNS (http://www.k8dns.com/balun.html).

After collecting the various pieces of gear I would need (thanks Wal VK4CBW for 21 feet of RG58), I proceeded to build this simple choke.

I wound the entire length of coax on a piece of PVC piping I had in my workshop.

I wound the entire length of coax on a piece of PVC piping I had in my workshop.

I held the coils in place with zip ties, then soldered on the PL259 connectors.

All ready for connecting up to my end-fed antenna at the feedpoint.

All ready for connecting up to my end-fed antenna at the feedpoint.

I connected it up to the end fed 80-6m portable HF antenna matchbox system, the UJM-150 that I purchased from Nelson Antennas and put it to the test.

All in place and ready to operate.

All in place and ready to operate.

Initial tests were disappointing: my touch lamp still turned itself on when I transmitted a test signal. Undeterred, I then added two ferrite chokes to the antenna feedline inside the shack and this solved the problem.

One of the ferrite choked taped to the antenna feeder.

One of the ferrite choked taped to the antenna feeder.

The other thing this new setup solved is my ability to tune up on 80m!

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One thought on “Building an all-band HF Air Choke

  1. Hi Grant, I guess you don’t have space for an OCF? Thanks for sharing your experience with your antenna set up along with RF in the shack! With your antenna in the air, might we hear you on air chasing SOTA (CW)?

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