K7lxc wrote:
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.
-0-
Steve, Is it possible that your proximity to the lower 'leg' of this
loaded vertical
dipole caused detuning? One way to find out what's going on is to
take an electrical
halfwave of coax and measure there.
n2ea
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