>
>COPY OF EMAIL FROM IAN G3SEK TO ME FROM THE OTHER DAY:
>
>
>
>Hello Luther
>
>
>>To summarize what I understand (please dissect, clarify, correct and
>reply):
>>
>> The crest has nothing to do with the amount of power or the cycle,
>>itself. It has to do with identifying a cycle to measure.
>
>You got it!
>
>>So, first locate
>>the crest - in fact, locate the highest crest that is transmitted in order
>>to measure for legality.
>>
>> Then, within that crest pick the cycle with the highs voltage peak
>>and measure its power.
>>
>> As a practical matter, that crest will consist of thousands of
>>cycles (e.g., if the crest is 1/10th of a second in duration and one is
>>transmitting on 3.795 MHz then there would be something like 379,500 FR
>>cycles within that crest). And, most all of the cycles within that crest
>>would have the same voltage peak. Right so far?
>>
>It's probably much shorter than 1/10th of a second. The narrowest,
>highest peak could be at the upper frequency limit of the modulation.
>Say that is 3kHz, so one audio cycle will be about 333 microseconds in
>duration. If it's a sine-wave modulation, the crest value will hang
>around within 1% of the absolute maximum for about 9% of the time (the
>top of a sine-wave is pretty flat) so that is 30 microseconds. At the
>crest of the modulation, that gives you about 111 cycles of 3.795MHz RF
>that are all within 1% of the same peak (and RMS) value.
>
>So, it isn't quite as many RF cycles as you thought, but still plenty to
>hang a measurement on!
>
>> So, to obtain power of that cycle, just apply a power formula to
>>.707 peak voltage - - I guess is that is because we can't hear the highs
>and
>>lows of a cycle - we can only hear the average of it - it occurs too fast
--
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