jeremy-ca wrote:
>By going from the conventional to the crossover method I was able to
>get a G5RV to cooperate that I was using at the summer cottage decades
>ago. No amount of twidling of the conventional turns worked.
>At that time and a few hundred miles from the test equipment at work I
>was more interested in getting on the air than the whys. Obviously I
>had found a "sweet" spot.
>
That can easily happen, as the equivalent lumped capacitance is only a
few pF so the resonant frequency is extremely sensitive to small
variations in strays. Even a twisted-wire 'gimmick' capacitor connected
end-to-end to the outside of the shield can move the resonance by a few
MHz at 20MHz.
If I desperately wanted to trim the resonance to some exact frequency,
the best way would probably be a gimmick cap with a GDO. However, the
peak is usually large enough and broad enough to make that degree of
refinement unnecessary.
--
73 from Ian GM3SEK
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