Paul Burridge wrote:

On Thu, 30 Sep 2004 09:41:43 -0700, Bill Turner
wrote:


Peak-to-peak voltage has no meaning when computing power. There is no
such thing as peak-to-peak power.


Why not? p-p power is essentially "peak envelope power" isn't it? Are
you saying there's one rule for RF and another for audio??

A: There is such a thing as peak-to-peak power, it's just not generally
very useful -- an example would be a 10Vrms sinewave drive to a 10 ohm
capacitor. The instantaneous power going into the capacitor would peak
at 5W and the instantaneous power going out of the capacitor would peak
at 5W. If you defined delivered power as positive and returned power as
negative then the peak-to-peak power would be 10W -- but you would
almost never care.

B: P-P audio power is _not_ the same thing as "peak envelope power", at
least not as defined in the US. Peak envelope power is average power of
the RF at the peak of the envelope -- so if you are running sine-wave
modulated AM with a PEP of 1500 watts into 50 ohms the peak _envelope_
power happens at an _rms_ RF voltage of 274V -- but the _peak_ power
happens at the RF voltage peak of 387V, or 3kW.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com