[UK-CONTEST] Quest for QRO

[Paul O'Kane]

----- Original Message ----- 
From: <g3ory at lineone.net>
 
> I think this is a bit unfair. I don't recall that anyone
> ever claimed  that a 150W dc input Class C AM PA would
> give 400W pep of ssb out.  This is not the basis of
> equivalence that was or should have been adopted.

I believe that's exactly what happened, intentional or
otherwise.  The fiddle was to confuse Peak Instantaneous
Power with Peak Envelope Power (PEP).

150 watts DC input (Class C AM) typically gives 100w o/p.
At the instantaneous 100% modulation peak, the waveform
voltage is doubled and therefore the instantaneous peak
power o/p is 400w.

That's why those who should have known better, and perhaps
did, argued that that 400w PEP o/p on SSB was required to
give the same o/p voltage as fully-modulated 150w i/p on AM.

It was a very successful con job because, as is now accepted,
PEP is effectively the same as RMS - power measured over time 
(one or more RF cycles) - rather than power calculated at
the instant of peak modulation.

A 150w i/p class C AM transmitter gives a 100w o/p CW signal.
A 400w o/p PEP SSB transmitter gives a 400w o/p CW signal -
Proof: feed the microphone socket with an audio tone to
get your CW - or just whistle :-)

73,
Paul EI5DI