[TowerTalk] Feedline (choke) question

[Tim Duffy]

I agree with Jim , K9YC recommendations.

I also have had success installing high current mode chokes on the coax to
the shack right at the amplifier output. Also sometimes a high common mode
choke from the radio output before the amplifier input can be effective.
Always at the antenna - always at the phasing/matching box. These must be
high CMI chokes in excess of 4000 ohms at the frequencies of interest. Good
quality ferrites and good quality connectors.

73
Tim K3LR

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Jim
Brown
Sent: Thursday, September 25, 2025 10:24 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Feedline (choke) question

On 9/25/2025 4:01 PM, Gary Smith wrote:
> Just connect the coax to the phasing bars directly or do as suggested by
byMosley which is make a six turn choke near the phasing bars or go without?

My detailed recommendations, based on nearly 20 years of research, are 
here. http://k9yc.com/2018Cookbook.pdf

In general, I recommend the matching system or "balun" recommended by 
the mfr be used, with a choke based on my designs added between that and 
the feedline.

73, Jim K9YC


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