In a message dated 12/12/01 7:01:41 AM Eastern Standard Time, w8ji@akorn.net
writes:
>
> > Guys, all I asked was whether I could do any harm to my transceiver by
> > operating it into a high-SWR load, or at least one high enough to
> > cause the output power to be folded back by the protective circuitry.
>
> I wasn't answering your question, because no one can answer it.
> The only answer is if it didn't blow up, it is probably OK.
I can answer it :-)
You most likely will be stressing the circuitry in the transmitter. Depending
on the SWR cut back protection circuit and its time constant, there could be
glitches of overload on final transistors before the circuit cuts back and
you would be operating the finals on the borderline where protection circuits
take on. Let's say that protection kicks in at SWR 1.999, you would be
"allowing" finals to run with percentage of loss even if protection cuts back
the power.
I like to operate my power circuits without unnecessary hurdles. Antenna
impedance designed to match feedline, PA matched to feedline, exciter output
matched to PA input. Takes little effort, avoids potential problems
especially in the contests.
So the final answer?
It is better to let the protection circuits do their job - protect the finals
in case of failure (of matching circuits) rather than using it as "power
control".
Now the $10,000 question please?
Yuri
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