> > Some tuners won't tune a 1/2 wave wire, since the
> impedance is
> > 800 to 3000 ohms. There is an easy fix for this; put a
> doorknob
> > capacitor of 50 to 200 pF from antenna to counterpoise.
> Now
> > your tuner will probably be happy, because the impedance
> is
> > now in the 100's of ohms.
>
> Why?
>
> The impedance would increase with the capacitor, not
> decrease. The antenna is resonant Rick.
Maybe I wasn't clear: the capacitor is in SHUNT with
the antenna. Shunting a basically resistive load with a capacitor
will always decrease the impedance. This is a standard
trick with HF marine radios on boats with a random
height vertical antenna. If the antenna happens to be
an exact half wave on a needed frequency, the tuner often
won't tune w/o the doorknob.
>
> > You can even put the capacitor right at the end of the
> wire
> > and drop the counterpoise from that point (all outside).
> > Then connect the tuner to the door knob with coax.
>
> He needs a counterpoise as Jim suggested. No way around
> that.
Maybe I wasn't clear here either: "drop the counterpoise"
does not mean "omit the counterpoise". It means connect
a wire to the cold end of the counterpoise and let it drop
vertically from there to the ground. BTW, when your
antenna impedance is 1000's of ohms, you don't need much
of a counterpoise, especially if you feed the antenna/counterpoise
through a balun to keep RF out of the shack.
Rick N6RK
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