[TowerTalk] Loading a Pro-AM 160M on other bands?

[kd4e]

>> Is the coil and feed system on such a vertical such that trying to
>> load it on 80, 40, 20, etc. via an antenna tuner is a waste of
>> time?
> 
> Every loading coil has a self-resonant frequency somewhere above the 
> frequency it is used on for mobile operation. It occurs at the
> frequency where the distributed capacitive reactance is equal to the
> inductive reactance. A mobile loading coil should not be operated at
> or above its self-resonant frequency. As a data point, my 75m
> bugcatcher coil is self-resonant around 6 MHz, making it not useful
> on 40m.
> 
> 160m loading coils are large with lots of distributed capacitance.
> Odds are, they are all self-resonant before the 80m frequency is
> reached and certainly before any of the other HF frequencies. So, to
> answer your question, operating a loaded mobile antenna far above its
> resonant frequency is usually an extreme waste of RF energy. -- 73,
> Cecil, w5dxp.com

Could one shift the resonance for use on other bands using
a source of switched inductance at the base or perhaps
switched or variable capacitance?

Makes for a fun exploration of possibilities and an
education for me as to how these things work!

> Yep, at some frequency, the EM waves won't know that the coil even
> exists.

Would that be way up at 6M or are you thinking UHF or SHF?

-- 

Thanks! & 73, doc, KD4E
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