[CQ-Contest] Pre tuned Hf amps

k3bu at optonline.net k3bu at optonline.net
Mon Sep 25 12:02:35 EDT 2006

Another aspect of "cheap monoband amps" is that you could optimize the amp for particular band, without worrying about resonances in the tank/choke circuits, losses in shorted coil turns, band switches getting fried, etc. 
I have been using my "Monobandit" with plug in tuned PI-L inputs and output PI-L coils plus the extra suppression for harmonics using link coupled "tuner" and coax stubs in order to minimize the harmonics. Back in Toronto, in the middle of residential area, I needed a  good suppression of harmonics, especially for channel 2 and 4 from Buffalo TV stations with weak signal. The net result was that with amp in I had more suppression and weaker harmonics than from "LP filtered" exciter alone. 
So one can have all the harmonics suppression arsenal and band filters tagged onto the monoband amps and just switch the whole complex.
Also, I found early on that commercial amps have a problem with contest duty "perpetual CQing" mode and like to blow them mediocre transformers. So home brewed monobanders with pole pig transformers are way to go  (Ugly but worky-worky :-)
73 Yuri

> I agree with one of the respondents in this thread that you can 
> build 
> six single-band amplifiers out of robust parts for less than the 
> cost of 
> an auto-tune Alpha or ACOM. Or you can do like my friend K5GO 
> did and 
> acquire of six used AL-1500s. But with six amps it's easy to do 
> multis 
> or SO2R; to do these kind of operations with auto-tune amps you 
> need 
> two, so the "six cheap amps" approach is a LOT less expensive.
> 73,
> Dave/K8CC

Yuri Blanarovich, K3BU

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