[UK-CONTEST] Quest for QRO

[Ian White GM3SEK]

Paul O'Kane wrote:
>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.

PEP is defined as the RF power at the peak of modulation envelope. In 
other words, it means "RF power at envelope peak"  or more simply, "the 
power of your largest RF cycle".

The same definition of PEP appears in licences world-wide (thanks to the 
ITU, presumably). The term "RMS" does not appear in the definition 
because it is redundant.

100W of carrier with 100% high-level AM equates exactly to 400W PEP. The 
person to thank for getting that right - and making sure RSGB and the 
licensing authority got it right too - was G2DAF.



-- 

73 from Ian GM3SEK