If you've not already done so, I'd first try to isolate the feedpoint
with a good current Balun (choke), like from DX Engineering. The
antenna may be using the coax as part of the antenna. But then I'm
not an engineer either.
73 Gary NL7Y
On Nov 20, 2008, at 2:23 PM, K7LXC@aol.com wrote:
> Howdy --
>
> I recently installed a Force 12 80M Sigma. It's like an H on
> it's side
> and fed asymmetrically which means the feed is off-set so you can
> reach it
> from the ground. It's a shortened antenna so it's got big loading
> coils at the
> feedpoint.
>
> I got the antenna to resonate at the proper frequency (3.775
> or so) with
> decent SWR (1.3 or so to 1). But as soon as I hook up some coax to
> it, the
> resonance goes up 75 kHz or so and the SWR goes to over 3:1. I
> tried 2 coaxes
> - 50-75 feet of RG-8X and RG-8. It seems like the coax is
> transforming
> something but I don't have any idea what's going on or how to fix
> it. Any ideas are
> appreciated. Help!
>
> We're going to contact F12 but don't think they'll be able to
> help since
> the new owner is not an antenna engineer, did not design the
> antenna and
> probably doesn't have any hands-on experience with the antenna.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
>
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