[TowerTalk] Force 12 C31XR Modeling

[Max Cotton]

The C3SS is a fantastic antenna, I put one up as a temporary about 7 years ago and it is still there, in reverse it works very well on 17 and 12M being very light is stands up to any weather too, I used a Hy-gain balun with no issues and it easily copes with full power.
73, Max M0GHQ

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From: TowerTalk <towertalk-bounces at contesting.com> on behalf of Jim Brown <jim at audiosystemsgroup.com>
Sent: 21 February 2023 19:08
To: towertalk at contesting.com <towertalk at contesting.com>
Subject: Re: [TowerTalk] Force 12 C31XR Modeling

On 2/21/2023 9:47 AM, David Needham wrote:
> I came
> up with that the impedance of the transmission line must be about 120 ohms
> to get the approximate curves with the stock dimensions.

A pair of #12 THHN taped together is in the range of 105 ohms (two
colors to keep track of polarity). Twisting the pair would likely raise
Zo slightly. I see zero reason for a third conductor. With a line that
short, I would not expect Zo to be critical.

We've often used a C3SS when operating portable for CQP and 7QP county
activations, and found that it is very picky about chokes. It does like
the right number of turns of #12 THHN around a 2.4-in o. d. #31
Fair-Rite toroid.

73, Jim K9YC
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