I would expect this degree of fiddling with a homebrew antenna, not
something "engineered" to the degree of an F12.
Why is this accepted? Send it back and demand a refund.
73, kelly
ve4xt
----- Original Message -----
From: <RLVZ@aol.com>
To: <towertalk@contesting.com>
Sent: Thursday, May 09, 2002 8:03 AM
Subject: [Towertalk] Force 12 needs to do more homework
> Force 12 needs to do more homework. It should not be necessary for the
> consumer to have to do all this work (take the antenna down and modify it
> several times) to make a mass produced factory built F12 work properly.
> Richard- K9OM
>
>
> Dink
>
> I have a C31XR up at about 70 ft fed with three seperate feeders. Each
> antenna is fed with 50m of HD100 coax and each has a choke balun of 12
turns
> of coax with a piece of 6 inch dia plastic water pipe as a former so the
> turns don't bunch up.
>
> SWR on all bands is at 1.1:1 or better at my chosen centre frequency.
These
> are 14100, 21200, and 28200. These c/f give me good swr across CW and
> sideband segments. To achieve this I removed the tips from the 15m
> element,added extra length to the 20m element and used hairpin matches on
> all three driven elements. These took some fiddling with to achieve best
> effect.
>
> The above swr readings were taken with the feeders to the other two yagis
> open circuit. Any kind of load placed across the 20m coax whilst using
15m
> messes up the SWR on 15m. This has caused me a problem in my SO2R set-up
> which I have worked around by putting a 15m parallel tuned circuit in
series
> with the 20m feed. I used a small L and big C to minimise the effect on
my
> 20m SWR. It's a compromise but it does work.
>
> With good choke baluns on each driven element I have found SWR to be
> substantially independent of feeder length. That is with 50m and longer
> feeder I haven't tried with feeders shorter than 50 metres.
>
> BTW You did remove the tips from the 15m elements didn't you? The 15m
> elements as delivered are too long for the separate feeders option.
>
> I have added a Cushcraft XM240 at about 85 feet (turned 90 degrees to the
> C31XR) and I have inverted vee dipoles for 160m and 80m hung just below
the
> C31XR. None of this seems to have had a materially adverse effect on swr
or
> performance of the C31XR so far as I have been able to judge.
>
> I hope this helps.
>
> 73
>
> Bob 5B4AGN
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