[AMPS] 'No tune' amplifiers

[Peter Chadwick]

Years ago, there was an article in the old Ham Radio magazine on this. As I
remember it, there was a more than usually complex circuit to do the
matching over a wider than usual band - something akin to the 2 inductor, 2
capacitor circuit that Warren Bruene has written up. Typical bandwidths were
of the order of 400KHz at 14MHz at 1 dB down. I have a suspicion that it
probably needs a reasonably well matched load.

If you are prepared to use a lot of components, then you can use cascaded
filter sections to get a Tchebycheff response for a relatively wide band
match - suggestions have been up to ! or MHz at 15MHz.

I still think you're better off with autotune. Loading can be easily done
with diodes sniffing samples of plate and grid volts. Put the diodes in
opposite polarities and sum them so the net result is zero when the loading
is right. The plate tuning is for maximum output from the plate voltage
detector. Phase detection is fine, but has difficulties - probably less
these days, since dividers and digital phase detectors make life not too
difficult.


73

Peter G3RZP

--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm