[UK-CONTEST] Quest for QRO

[g3ory at lineone.net]

David,

You wrote:

>>>Technically a falsehood as a 150w DC PA could never give 400w 
PEP output with good IMD performance.  This, in my view, was a 
bureaucrat's face saver and nothing else to enable us to run 400watts 
out rather than 100.

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.

IF the high level modulated 150W PA gave 150 W of unmodulated carrier 
OUT then, when you spoke into the mic and the big audio modulator 
contributed a bit to the effective input power (remember aerial 
ammeters move upwards when you speak into an AM transmitter (or 
should 
do!)), the pep out at 100% modulation would be 600W.  No question 
about this I am afraid! [ Just think that at 100% modulation the 
output 
peak voltage doubles to twice that of the quiescent carrier, so the 
power has gone up by 4 times. That is 150W to 600W]. The idea was 
that 
the power licensed with ssb should give the same pep as could be 
realistically achieved with AM high level mod.
The question that was then presented is 'what was a realistic 
estimate 
of the efficiency of a Class C PA in a high level modulated 
amplifier, 
since the old licence conditions referred, as you say, to 150W dc 
INPUT 
and not output as I used above'?  The figure of 66% was settled upon 
although some folk claimed they could do better than that!! Hence 
600W 
x 0.66 = 400W pep. Perhaps the efficiency chosen gave a rather 
convenient round number as an answer and maybe the bureaucrats 
contribution was to deny us an assumed efficiency of 75% instead of 
66% 
and prevent us from running 450 watts pep out.

73 Bob
G3ORY


>----Original Message----
>From: g3yyd at btinternet.com
>Date: 22/02/2009 14:18 
>To: <uk-contest at contesting.com>
>Subj: [UK-CONTEST] Quest for QRO
>
>What a chain of "reflections", which is, of course, what a reflector 
is 
>about.
>
>I also take into account Don's. G3XTT, comments under the Mega 
Station 
>subject line. The difference between 1500w and 2Kw is not much 
unlike 
>the difference between 400 to 1500. As I see that Lynch, Vine Antenna 
et 
>al do a good trade in 1500 watt amplifiers I am sure there are many 
>stations this weekend sending 5NN4TT who are understating the 
situation. 
>Of course we may be in a situation that comes under the heading of: 
"You 
>do not say and we will not ask". Most of the 1500 watt amplifier are 
key 
>down for ever types so the old excuse of running at 25% output does 
not 
>wash with me.
>
>The problem comes to those who generally want to abide by the 
licence 
>but at the same time do not want to be at a competitive 
disadvantage. 
>They have an ethical dilemma, to run 400 and be at a competitive 
>disadvantage or run 1500 and operate outside the licence conditions. 
If 
>you are highly competitive then the decision is obvious, if on the 
other 
>hand you believe in the rule of law then you run at a competitive 
>disadvantage. Why should we put people in this position? They could 
>avoid it by going to the lower power categories but there is 
something 
>compelling about going for the "top" category especially for those 
who 
>are highly competitive.
>
>I and many others on this reflector will remember the time we had 
>150watt DC input restrictions except top band with 10watts DC input. 
I 
>can remember competing in RTTY contests in the early 70s when that 
meant 
>no more than 100 watts output or may be 110 watts if the PA was very 
>efficient. Then some one came up with the idea that 100% modulated 
AM 
>with 150w DC input became an output of 400 watts of Peak Envelope 
Power 
>so we could run that on SSB and then a bit later all modes became 
400 
>watts PEP. Technically a falsehood as a 150w DC PA could never give 
400w 
>PEP output with good IMD performance.  This, in my view, was a 
>bureaucrat's face saver and nothing else to enable us to run 
400watts 
>out rather than 100.
>
>We used to have no alternative to using normal length callsigns and 
that 
>has been changed to allow calls with just 3 or 4 characters for 
>contesting. This was done so that contesters were not disadvantaged 
>compared to the international competition. So why not 1500 watts of 
>legal power as we are not disadvantaged compared to the competition 
>unless of course we throw individual's ethics out of the window and 
>operate a "You don't say, we won't ask" policy. Unless some one can 
>think up another bureaucratic face saver?
>
>David G3YYD
>
>
>
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>





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