I suspect that the filter netwoks in this Amp prevent it from being used
too far out of frequency. Is that true?
For instance, let's say that I need to be on a frequency close to 5 MHz.
I cannot get more than about 100 watts out of the amp. However, if I am
just above 4 MHz, I can get full power out. So - it must be a filtering
issue. In this case, I am keeping the BAND switch on 80, and the PLATE
ends up around the 40 section, and LOAD is between 5 and 6. I have tried
other positions, and nothing works nearly as well as this - but this
position only gets about 100 out.
::The pi-L plate tank network is low-pass in nature, so to operate above 4.0
MHz you should use the 40m, not the 80m, position in order to get the plate
tank to resonate. Problem remains with the tuned input network, though:
It's tuned to 7 MHz, not 5 MHz, and needs to be retuned or maybe even
modified to provide a reasonable match to your transmitter at 5
MHz.-WB2WIK/6
Now - is there a mod for the amp that would allow a wider range to tune??
Or, do I give up on this amp for MARS usage?
::It's an amateur amp, not a general-coverage one. There have been various
amps manufactured over the years that have continuous tuning, both input and
output; that's an expensive accomplishment. One example I can think of,
which was very popular at MARS stations, was the old Henry 4K Ultra. They
go on the used market today for 2-3x what a new AL-80B costs, but do provide
continuous tuning. The even older Collins 30S1 is another example, and
ditto on the price.-WB2WIK/6
Thanks in advance.
--
73 de Tomas, NW7US (AAR0JA/AAA0WA)
: Propagation Editor for CQ, CQ VHF, Popular Communications :
: Creator; live propagation center http://prop.hfradio.org/ :
: Associate Member of Propagation Studies Committee of RSGB :
: US Army Miltary Affiliate Radio Service (MARS) SMD AAA0WA :
: 122.93W 47.67N / Brinnon, Washington USA CN87 CW/SSB/DIGI :
: Website/software/database design http://newwebmakers.com/ :
: 10x56526, FISTS 7055, FISTS NW 57, Lighthouse Society 144 :
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