Jim Reid wrote:
>To set correct, the amplifiere output circuit
>must be retuned and the load capacitor readjusted!
>
>I didn't do that in yesterrday's tests!
OK! Now it makes sense. Yeah, you gotta retune for different loads.
There will be SOME variation because as others point out, the SWR meter
is really designed to optimally work in a relatively 50 Ohm environment.
Yet, in some ways that's contradictory because if you always had a 50 Ohm
environment, why would you need an SWR meter?????
So yes, repeat what I suggested but retune the amp each time.
One other thing that I wish to point out in what you read:
It sounds like the author described very well what needs to occur for
maximum power transfer. To restate, the amplifier must be conjugately
matched to the impedance of the antenna system at the output of the
amplifier. If a conjugate match occurs, maximum power transfer takes
place. If a conjugate match does not occur for any reason then some
power is reflected back to the amp and essentially is dissipated as heat.
Now, the way most hams who don't run tuners match to their antennas is
with the loading cap. They adjust that loading cap for maximum power
out. But I argue that just adjusting the loading cap is not necessarily
going to be what gives you a conjugate match. To really properly adjust
for optimal power transfer without a tuning network, one would need to
adjust all three elements of the pi-network - Ctune, Ltank and Cload.
Unless you have a roller inductor, this isn't practical. So you do have
a tradeoff. Tuning just the load cap will get you close but will not
necessarily give you an optimum solution. Then again if you get out
legal limit, who cares!
73,
Jon
KE9NA
--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!
Jon Ogden
jono@enteract.com
www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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