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[KD7RDZI2]

I've carefully said "load impedance" in this explanation rather than
"SWR".  It has nothing to do with the SWR on the feedline, just the
resulting impedance that the transmitter sees.  For example, an
SWR of 2 : 1 might yield a load impedance of 100 + j0 ohms, or
25 + j0 ohms, or 75 - j35 ohms.  The transmitter likely will
respond differently to each of those values:  some might reduce
distortion, some may increase it, depending on the design.

The only issue here is "depending on the design", which the appliance operator neglects. To be very practical, check as WA3SKN suggests your own modulation with a separate receiver. A remote SDR such as http://websdr.ewi.utwente.nl:8901/ is very useful to check whether it sounds distorted. Another method is using an antenna switchbox such as the MFJ1708 or alike and listening with any receiver (add also -40 db attenuator if you can between the receiver and the switchbox). There is no better judge than yourself.

[WB6BYU]

If one applies the 'right' coding and sacrifice some of the 256 possible states, it is possible to gain up to 10dB or more output power capability by removing those states where all the signals add in phase and amplitude...

True, Peter, but we had no control over the equipment in which
our parts were used.  Sometimes we got complaints of a 50%
failure rate, but couldn't get any information on the conditions
in which they were operating it.  You probably are familiar
with such issues...

Often this was because some other vendor was providing that
particular part of the circuit, and the details were confidential.

A classic case was was where the WiFi receiver worked perfectly
well on weak signals, but failed when signals were stronger.  Our
preamp chip was tested with the higher signal levels, and worked
just fine.  This was puzzling.

After thinking about it, I guessed that the receiver likely listened
with the preamp enabled, to hear weak signals.  When a signal
was received that was strong enough, the preamp was bypassed.
This happened for each individual frame.

It turned out that the bypass switch took time to operate:  on the
bench we could see the amplified input signal drop out, then come
back at the lower level with the preamp bypassed.  But if that
dropout time was too long, the first bits of the frame header (which
contained the data required to decode the frame) got clipped off,
and that frame was lost.  Of course, the customer had not given
us any specifications for switching time...


So there are other factors than signal distortion to be considered.

[G3RZP]

One thing you learn early on as a semiconductor applications engineer is that you cannot predict what customers will do with the parts. We had a PLL FM IF/Demodulator device that was meant for use preceded by an IF filter before the limiter. A customer in Taiwan had ordered 60,000 devices for cordless 'phones and complained that they didn't work. I got out there  and discovered that to save money, the engineer figured that the PLL demodulator would provide all the IF selectivity needed. But of course, the limiting amplifier negated all that......

Or the customer who laid out his PCB on the basis that the IC pin out was shown from the package top and he had laid out the PCB on the basis that the pin out diagram was from bottom - despite the note on the data sheet. So they demanded that FOC, we redesign the IC or pay for all the expensive Teflon circuit boards that they had to scrap....