[Lf] Resonance and Impedance change in the winter season]

[Andre' Kesteloot]

Toni Bärtschi wrote:

> 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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