> -----Original Message-----
> From: Tom W8JI [mailto:w8ji@w8ji.com]
> Sent: Monday, October 16, 2006 1:02 PM
> To: Gary Schafer; 'Ian White GM3SEK'; amps@contesting.com
> Subject: Re: [Amps] PEP power..
>
> > To add a little more clarification to Ian's nice
> > explanation;
> > The AVERAGE power that Ian is describing is what many
> > (incorrectly) refer to
> > as RMS power of the RF.
>
>
>
> ALL the power is the effective heating or work power, and
> since the RF cycle is a sine wave it is derived from the RMS
> voltage and/or current. If we take the peak voltage of the
> RF sinewave (it is always a sinewave) and multiply it times
> .707 and use E*2/R, we have the power. Roy and others may
> not like it and indeed it is technically incorrect, but it
> is so well established and makes so much sense to the layman
> RMS will always be the words people use. This is true even
> if average or mean is technically more accurate.
>
>
>
> As a matter of fact using the word "average" creates more
> problems than it solves.
I think using incorrect terms creates more problems. Long ago when I first
read the FCC's definition of peak envelope power I saw the word "AVERAGE" in
there, not RMS as most would expect when describing what they were talking
about. I could not figure out how it could be average power when it looked
like it should be RMS in the definition. After I learned that RMS power is
not a real term I then understood.
Why would we not want to promote the proper terminology? Not only is the
wrong terminology a problem with the definition of pep but it also comes up
in many other areas when reading about how things work.
>
>
>
> The problem comes in because Hams often call "average power"
> indicated by a power meter when looking at a varying
> envelope RMS power. We read average and peak envelope power,
> not RMS and peak envelope power. The average and the peak
> are based on the work power of the sine waves, one being the
> highest effective power of the envelope and the other being
> the average power of the envelope.
Average power as read on a wattmeter on ssb would probably be better
described as AVERAGE VOICE POWER to distinguish it from the average power of
the individual sine wave.
>
>
>
> To a lesser extent Hams assume peak envelope power is where
> peak RF voltage is multiplied by peak current, or where
> instantaneous peak current or peak RF cycle voltage is used
> with resistance to find some fictitious power that really
> isn't related to work.
If that peak rf voltage is multiplied by .707 to find the rms value of that
voltage and then divide by the resistance it is measured across we find
average power which is the pep in this case.
>
>
>
> When we say peak envelope power is "based on the average
> power", we would have to say the "average power" is the
> average of the average power of each RF cycle over a period
> of time. Either way is confusing.
If we want to refer to the average power of a voice modulated signal maybe
average voice power would be an appropriate term.
>
>
>
> It would be accurate and less confusing to say peak envelope
> or average power is the peak or average of the effective
> power, work power, or mean power when dealing with the RF
> cycle power, even though it is indeed based on the RMS
> voltage or RMS current of each RF cycle.
I don't know if it would as I really don't understand what you are saying
here in this paragraph and I know that you do understand the differences.
>
>
>
> > Peak envelope power has nothing to do with "peak power".
> > It is all to do
> > with average rf power.
>
> Peak envelope power is the highest envelope value of power
> that does work. It is all about the RMS voltage of the
> individual RF cycles times the RMS current of the RF cycles.
Yes and when you multiply rms voltage by rms current you get average power
not rms power. The rms term goes away.
>
>
>
> Look at this example. If I pick a capacitor I have to choose
> the rating based on the peak RF voltage. That is the voltage
> seen on a scope at the crest of the highest sinewave, or on
> a meter that charges to the highest crest of the RF sine
> wave cycle. That voltage is not the same as the effective
> voltage that heats a resistor or does some other form of
> work. We'd have to use the RMS voltage to calculate power.
>
>
>
> This is why people use the term RMS power, not because the
> power is RMS but because the power is derived from the RMS
> voltage and/or current rather than peak voltage and/or
> current.
But it is not rms power it is average power. Why not use the proper term?
Rms power does not exist. The rms term goes away when we multiply rms by
rms.
If we wanted to know what peak power was then we would use peak voltage and
peak current for calculations.
To find average power we use rms voltage and rms current.
>
>
>
> The reason people get confused is because many engineering
> terms are ambiguous. The important thing is people get the
> correct picture in their minds.
Helping get the correct picture in our minds I think starts with using the
proper terms. Especially when the fcc definition of peak envelope power uses
the term "average power" and not rms power. By continuing to use the
improper term rms power it obviously confuses many when trying to relate.
>
>
>
> 73 Tom
>
73
Gary K4FMX
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