Here I'm using now an LF match box in the shack, so it's no longer
necessary to go outside for fine tuning.
It's a PI-configuration with parallel C's at the in and output, they can
be switched in 5nF steps up to 50nF. The serial Inductor is a 28uH
roller type and I can switch-in additional L up to 150uH if needed.
Now I can leave my base coil in a standard configuration and adjust to a
1:1 SWR (my TX likes it) with the PI-filter. Very nice, especially at
night, when it is snowing outside, hi.
An interesting detail: The russian door-knob condensers I bought in
Friedrichshafen were all dead, but I was lucky and found a box of large
american mica condensers I had put away some 20 years ago - still the
better stuff, hi.
73 de Toni, HB2ASB
Hans-Joachim Brandt schrieb:
Toni Baertschi schrieb:
> >From HB9ASB, JN36pt
>
> PS. Actually it is very cold here and my antenna de-tunes from hour to
> hour as the soil is freezing deeper and deeper. Not only the resonance
> goes higher, the impedance is also changing and it is difficult to
> follow this developement with the existing matching circuit.
Now, during winter time I can make the same observations. Before I have just
experienced small changes in resonance, but now, in the cold, not only resonance
changes considerably but also VSWR increases to S = 2 at optimum tune (I am
using a 50 ohms feeder cable between PA and LF antenna). Therefore I also have
to revise my fine tuning and matching circuitry to cope with these effects.
73 Ha-Jo, DJ1ZB
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