That could be the source of the higher than normal SWR on 12. The factory
specs are for "~3.2" with 100 feet of RG-213, although I run 70' of RG-213,
connected to 50' of 7/8" Heliax and get around 5:1. I measured the SWR with
a Bird 43, and confirmed with an MFJ 259 which shows R=17 ohms.
Fortunately, the length of coax causes the SWR meter on the linear to read
about 1.5:1 on both 12 and 17. Readings and bandwidth on 40, 20, 15 and 10
are almost exactly what the factory specifies, if not maybe a bit better.
Maybe I should leave well enough alone!
Ron
N6AHA
-----Original Message-----
From: Pete Smith <n4zr@contesting.com>
To: Ron Castro <ronc@sonic.net>
To: <towertalk@contesting.com>
Date: Sunday, January 24, 1999 7:57 AM
Subject: Re: [TowerTalk] Adding 12 Meters to C4
>At 12:14 PM 1/23/99 -0800, you wrote:
>>My SWR runs around 5:1 on 12, so the losses are substantial. Since I have
>>an RCS-8V remote coax switch with two unused ports, I was thinking about
>>maybe a vertical dipole off the boom, or something else horizontal, or in
a
>>quad configuration mounted on the boom. Any thoughts?
>
>That's distinctly a non-standard SWR on 12! Haver you considered the
>possibility that you are getting severe interaction with the 80-meter short
>dipole at only 3-foot spacing. 12 meters is the 7th harmonic of the bottom
>end of 80, so it's possible your C-4 is seeing the dipole as a
>low-impedance load nearby.
>
>I would not do anything on or near the boom of the C-4 -- within 6 feet or
>so -- because you're far more likely to mess it up than you are to come out
>with an antenna for 12 that will work well. with my kind of bad luck, you
>would wind up with a messed up C-4 AND no performance on 12.
>
>73, Pete Smith N4ZR
>n4zr@contesting.com
>
>Loud is.
>
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