[AMPS] Automatic tuning of a VHF amp

[Dave Kirkby]

Hi all,
      my latest VHF triode amp is going to use stepper motors to control
the anode tuning and possibly loading, for two main reasons:

1) That way I can get the controls in the best position on the front
panel.
2) It will allow remote (but manual) tuning of a noisy amp.

I'm contemplating making the tuning automatic. Does anyone have any
ideas of how it can be done ? I faintly remember seeing something about
adjusting the tuning until the anode impedance is completely real (i.e.
at resonance), but have no idea how it could be done. The cathode tuning
is less of a problem, as its not likely to need changing for small
changes in frequency, but there adjusting for a real impedance should be
easier, if not exactly trivual.

One possibility is to store previous locations of the stepper motors in
an EPROM/EEPROM, but I don't like that idea. My main reason for
contemplating this is to ensure the amp will be properly tuned if used
by someone else in a different antenna (ie contest). There is little
point storing my own settings there.

Are there any commercail VHF (or even HF) amp that do automatic tuning ?
My guess is there are. Any thoughts appreciated.

--
Dave Kirkby G8WRB
Department of Medical Physics,
University College London,
11-20 Capper Street,
London,
WC1E 6JA.

Tel: 0171 209 6406 (International +44 171 209 6406)
Fax: 0171 209 6269 (International +44 171 209 6269)



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