[Icom] re pro output power]

[George, W5YR]

You are welcome, Andy. Sounds like you have your setup all tuned up and
working fine.

I hope that my ascension to the pulpit on the subject of SSB modulation and
mics, etc. prompted some folks to remember that with SSB or any
time-varying modulation, meters seldom tell all the story. Since SSB began
in amateur circles in the 50's, it has been clearly understood that only
with a scope can one determine what a SSB transmitter and/or amplifier is
doing. We continue to be provided with meters, though, and our collective
technical skills have degraded to the point that we now tend to look upon
the meter readings as a true indication of operating conditions.

Under certain specific conditions, meter readings can be accurate
reflections of the state of our equipment. For example, for key-down CW the
wattmeter reads correctly the PEP output of the transmitter. For a string
of dots, we expect the reading to drop 50% due to the dot/space duty cycle.
For an AM transmitter, the unmodulated carrier reading on the meter is a
true indication of carrier power level. 

But, in the realm of SSB, only certain specific modulation waveforms with
predictable mathematical properties can be used with expectation that
meters will tell the truth. The classic example, of course, is the two-tone
signal which has the property that its average power is one-half its peak
power. And the three-tone signal with a 3:1 ratio. And so on.

With random speech waveforms, however, all bets are off and a scope is
really the only monitoring instrument that shows what is *really*
happening.

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437

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awallacejr@charter.net wrote:
> 
> George-
> 
> Thank you for this very informative analysis. I drive my 4KL with about 60
> watts out of my 756Pro--which puts out the full 1,000 watts from the
> 4KL---and notice no distortion. I don't rely on ALC with the 756 Pro set to
> maximum power and I use an Icom SM-20 microphone. When I operate barefoot, I
> back off on the 756 Pro power a little--put out maybe 80 watts--which 20
> watts difference appears to be unnoticeable from "full" power to folks on
> the other end of my transmissions.