The Hustler BTV series are great antennas. But unfortunately Hustler tunes
them according to how a large majority of the amateur population (especially
new hams) use them; that is to bang a pipe into the ground, mount it, and
have at it. Measure the feedpoint impedance of one mounted in this
configuration, and you'll get about 55 ohms; near perfect match, and nice
bandwidth. With the very first radial you lay down, and feedpoint impedance
begins a slow decent. Depending on how many you lay down, and to some
degree their length you'll get a feedpoint impedance so low, that a gross
mismatch develops between the antenna and the 50 ohm transmission line.
First, resist the urge the cut the element sections! Instead, carefully
mark each trap and the adjustment overlap, and starting with the 10 meter
trap, adjust it slightly and check it. Do this with each trap until the
VSWR curve bottoms out within the desired band. The term "bottom out" must
be used loosely here because you still have that feedpoint mismatch. You
may never achieve anything below 2:1, but if you transceiver can tolerate a
high SWR, that antenna will work great. Another thing you will notice is
the bandwidth really tightens up, especially on 40 meters.This is a long,
painstaking process, but worth the effort.
Finally, if you want to correct the feedpoint mismatch, you can add an UNUN
(not a BALUN) at the feedpoint. A place like Balun Designs will wind you
1.56:1 transformer that will correct things.
Tom Hybiske, K3GM
----- Original Message -----
From: "Kelley" <kshaddrick@jetup.net>
To: <towertalk@contesting.com>
Sent: Wednesday, January 20, 2010 6:47 PM
Subject: [TowerTalk] Hustler 5BTV Problem
> I've been working with a 5BTV antenna for about two weeks now. I've got
> good SWR readings on 10m, 15m and 80m. Higher but usable readings on 20m.
> However, I can't get anything under 2.0:1 on 40m. The antenna is ground
> mounted with 20 25' radials. It's fed with about 60' of coax.
>
> I've tried the normal tuning as well as adjusting the traps. Nothing seems
> to bring the SWR on 40m down to something usable.
>
> Anyone have any ideas I can try?
>
> Kelley - W0RK
>
>
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