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Re: [TowerTalk] Adding an RF choke

To: towertalk reflector <towertalk@contesting.com>
Subject: Re: [TowerTalk] Adding an RF choke
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Mon, 2 Dec 2024 16:36:10 -0800
List-post: <mailto:towertalk@contesting.com>
On 12/2/2024 11:54 AM, Jeff DePolo wrote:
Why should the choke be made out of 75 ohm coax?  If the feeder Z0 is 75
ohms by design then, sure, it makes sense to use 75 ohm the choke section
and simply compensate for the added length, including the differences in VF
as you mentioned if different.  But if the feeders are 50 ohms or something
else, what's the benefit of the choke being 75 ohm cable specifically?

Of course, but most phased arrays are 4-squares, which use 75 ohm phasing lines, and that's what I assumed. :)

Also, note that the miniature 75 ohm cables listed in my 2018 Cookbook are rated for use in a 4-square at legal limit, where currents are much smaller than to a single antenna.

Thanks for the question -- I'm copying to the reflector so others will see.

73, Jim K9YC



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