On Sun, 28 Sep 2008 11:48:18 -0700, John Smith
wrote:

Cut power to 25% and the other guy will see (if his s-meter is accurate)
a drop to half the reading ... at 80% power, little difference, other
than if you were just above noise floor in the first place ... however,
"tweaking" an antenna to perfect match/design criteria has always proved
to we worth the effort ... and especially to my ears--but my s-meter
also ...

I think you mean guess-meter:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm
S-meters are notoriously inaccurate.

We have an Icom PCR-1000 remote receiver setup on a local mountain top
run by HRD (Ham Radio Deluxe) software. It's quite handy for tuning
and adjusting antennas and generating a polar plot for HF yagi's and
quad's. There are substantial site errors in doing it this way, but
it's still better than a field stength meter, or the traditional
"how's my signal" report.

I designed the 150w PEP power amplifier section for the Intech M3600
HF marine radio. Using VMOS xsistors, I was able to demonstrate
unconditional stability, at rated power, with any non-resonant load up
to about 8:1 VSWR. Above that the current went up a bit too high for
the 12 ohm load, and Vce climbed for the 400 ohm load. I might have
done better but didn't want to destroy the test radio. The radio was
specified to operate up to a 2:1 VSWR at full power and would reduce
power when the threshold reflected power was detected. Although I
demonstrated that it was possible to operate quite nicely up to 8:1
VSWR, without power reduction, nobody wanted to add that to the data
sheet for fear that someone would actually use it that way.

My guess(tm) is that most modern HF radios can also safely operate
into high VSWR loads, but suspect that manufacturers are also hesitant
to guarantee such operation. Most manufacturers don't even specify a
maximum VSWR and simply reduce power if excessive reverse power
(usually 2:1 at full power) is detected.

Disclaimer: If you trash your radio trying this without monitoring
the Pout, PA temperature, PA xsistor voltage/current, and checking for
oscillations on a spectrum analyzer, don't blame me.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558