When you say it is "resonant" at 7.7 MHz do you really
mean it is matched to 50 ohms? (NOT the same as resonance)?
The TAP for an Omega match needs to be closer to the center
than a Gamma Match. The Omega match raises the tap resistance
to 50 Ohms. If the tap is past the 50 ohm point, the shunt capacitor
will NOT be able to bring the feed impedance back to 50 ohms.
I used a sloping 3/4 inch aluminum (CATV hardline with the
end smashed and hose clamped to the boom) to feed on my
Omega matched TH6 boom. The tap was approximately 6 ft out.
This can be placed UNDER the boom if you have the clearance
(12 to 18 inches) on your mast.
de Tom N4KG
On Tue, 6 Feb 2001 19:33:42 -0600 "Mike Foerster"
<mike.foerster@home.com> writes:
> I have the boom on my TH11DX loaded on 40 meters using a gamma match.
> I
> isolated the truss wires and fed one side through a capacitor.
>
> Problem is that the closest that I was able to get to resonance was
> 7.7 MHz.
> I get reasonable results with a tuner to get it to match on 40m.
> The match
> box that I built actually contains an omega match, but I found that
> the
> extra cap wasn't much help.
>
> It appears that the system wants to have the truss connection moved
> out a
> few inches in order to be able to bring the match down to 1:1 on 7.2
> MHz.
> But that would mean taking the antenna down.
>
> I was wondering if the gamma match wants the connection farther out
> on the
> boom, or would it also work to add some length to the truss wire in
> the form
> of adding a bit of a loop (droop?) of wire between the gamma
> capacitor and
> the truss wire to make it appear that the line is longer?
>
> Can any one suggest an alternate solution to make the gamma match
> work at
> 7.2 MHz? (Cheat the cable into thinking it's fatter?)
>
> Mike
> W0IH
>
>
> --
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>
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