[UK-CONTEST] Quest for QRO

[g3ory at lineone.net]

Paul,

The licensed power in the olden days (when amateurs could only be 
'trusted' to have tolerably accurate dc instrumentation) was a bit of a 
mish mash. The CW rules were clear - 150W dc input which was likely to 
result in 100W rf output. At the same time 100% high level amplitude 
modulation was permitted. Under these conditions the total rf power 
output rises to 150W from the 100W previously. Hence the old rules were 
not consistent in terms of RF power output, more pragmatic.  Remember 
those big old modulators and the 'rule of thumb' that they had to 
produce half of the power that the RF PA produced under carrier only 
conditions. The reason of course was that this power went into the rf 
output (remember the aerial RF ammeter kicks upwards when you yell into 
the mic of an AM transmitter).

Then along comes a new method of modulation in which only the peak 
power can sensibly be defined since pretty much everything else is 
dependent on the nature of the modulating signal.  This made it 
sensible to redefine the method of power measurement since peak 
envelope power was a viable method of measurement for both AM and SSB.  
The pep output for a 100W carrier high level modulated is 400W (as we 
have already seen). Hence a unified method of power output measurement 
was introduced which was the same irrespective of whether the mode was 
CW, AM or SSB.  The highest level previously licensed was chosen and 
this of course is 400W pep. 

73
Bob

>----Original Message----
>From: pokane at ei5di.com
>Date: 23/02/2009 12:18 
>To: <uk-contest at contesting.com>
>Subj: Re: [UK-CONTEST] Quest for QRO
>
>----- Original Message ----- 
>From: "Ian White GM3SEK" <gm3sek at ifwtech.co.uk>
>
>> 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.
>
>I'm impresssed, but that is far from the full story.
>
>What I would like to know is why, exactly, did the permitted
>power on CW change overnight from 100w PEP (nominally equivalent
>to 150w DC input on CW) to 400w PEP?
>
>After all, it was not considered to be a general increase in
>power.  Therefore, it must be related to the change in definition
>of power.  Therefore, someone was conned, and it wasn't the
>amateurs - we were laughing all the way to our linear amps  :-)
>
>73,
>Paul EI5DI  
>
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