[AMRadio] PEP for AM


D. Chester k4kyv at charter.net
Sat Dec 30 12:33:15 EST 2006


---- Original Message ----- 
From: "Gary Schafer" <garyschafer at comcast.net>
>> -----Original Message-----
>> Subject: [AMRadio] PEP for AM
>> Anyway, I ran across this information, and thought I'd share it with the
>> group here, so that some mis-conceptions about AM PEP could be cleared 
>> up.
>>
>> (from: http://www.pc-oscilloscopes.com/articles/pc_oscilloscope_rf.html)
>>
>> P E P (AM)
>> % Modulation = (( PEP - PC) / PC) *100%
>>
>> Example:
>> Carrier Power PC = 100 W, PEP = 400 W.
>>
>> Determine % Modulation
>> M% = (( 400 - 100) / 100) *100% = ((20-10) / 10) *100% = 100%
> Hmmm, let's see, 400 watts -100 watts = 300 watts. Divided by 100 watts = 
> 3.
> Times 100% = 300% modulation..
>
> I think they forgot the square root of the powers in the formula.

Looks like that may add to the misconception.  But I'm not sure they left 
out the square root symbol.  Could that be the reason for the double 
parentheses on the left?  Since most word processing programs do not have 
easy access to mathematical symbols, and e-mail programs may not have them 
at all, a special set of symbols has evolved for mathematical expressions. 
I am not totally familiar with them, and I sometimes get totally lost when 
trying to interpret mathematical expressions posted over the internet.

Isn't this what the formula is supposed to look like?  (the problem is that 
it may not display correctly if your e-mail reader does not support 
Unicode).

                               ____      ___        ___
 % Modulation = ( √PEP -  √PC  ) / (√PC) *100%

Evidently "they" think that so few people would have a use for mathematical 
formulae that maths symbols are not included in the default character set. 
Just like the ricebox manufacturers who no longer include monitor scopes in 
their appliance product line.

Don k4kyv






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