[SADXA] PEP vs N Tone Average Power - Amplifier Tuning

[W7EXG]

Wes, A two tone gnerator in K3(S) IS a nice feature..since most low power
rigs are most likley to drive a linear. Nice to know Elecraft designers are
thinking.. I think there is value even  beyond two tones, and is the reason
for my discusion. Thanks!
Bill
----- Original Message ----- 
From: "Wes (N7WS)" <wes at triconet.org>
To: <sadxa at mailman.qth.net>
Sent: Wednesday, March 16, 2016 1:57 PM
Subject: Re: [SADXA] PEP vs N Tone Average Power - Amplifier Tuning


> Good stuff.  BTW, an Elecraft K3(S) has a built-in two-tone generator.
>
> On 3/16/2016 1:45 PM, W7EXG (Bill) wrote:
> > Hi SADXA Group..
> >
> > If you are interested in Key Down Tuning of your Linear Amp [without
frying
> > your output devices], you might find value in my comments below. No
Pulse
> > Tuning required.
> >
> > Most of you are probably familiar with 2 tone SSB testing:
> >
> > Key Points:  1. Two Tones of different non-harmonically related
frequencies
> > are used as input, but with identical amplitudes.
> > 2. Distortion/Linearity can be directly observed with scope
> > voltage (V) measurements across the load resistor (R).
> > 3. Average output Power (Pavg) is 1/2 the PEP output power
> > P(pep), while testing.
> >
> > NOTE: Pavg is defined by V(rms)^2/R for any waveforms, which defines the
> > Joule Heating of a load Resistor (R).
> >
> > At the Last SADXA meeting, I had mentioned the theoretical relationship
> > between P(pep), and an N tone Pavg.
> >
> > Basically:
> > P(pep) = N Pavg
> >
> > For example, using 4 different frequencies, but identical amplitude
tones, a
> > 1500W pep output will produce a 375W average output power.
> >
> > Most 1500W output PEP amps, can tolerate 375W key down average output
power,
> > during the 1500W PEP Output tuning process.
> >
> > Ideally, access to a peak-reading RMS calibrated Wattmeter would be of
> > value, since it should measure the RMS value of the non-sinusoidal
waveform
> > as well, and thus the correct average output power.
> >
> > NOTE: Most Watt Meters [with an AM or FM designation], are usually
accurate
> > in measuring Pavg, for the sinusoidal waveform. However, for
non-sinusoidal
> > voltages, these meters often determine average Value of the waveform to
> > determine the so-called Average Power. The DAIWA CN-101L series has the
FM
> > designation (only in the Manual).
> >
> > For the 2 tone case, the Average output Power on THIS DAIWA meter will
be
> > 40% of the PEP output power (not 50%). [2.5 Pavg] = P(pep)
> > For the 3 tone case, [3.75 Pavg] = P(pep)
> > For the 4 tone case, [5 Pavg] = P(pep)
> >
> > In general, a simple power test on any given wattmeter, can determine
the
> > ratio of PEP output power vs Pavg for N input tones for that meter.
This
> > ratio can then be used with the meter to tune the Linear Amplifier.
> >
> > I hope someone in the SXDXA will find value in these comments. I found
this
> > method useful, in testing my Drake L7 Linear Amp to maximum potential,
after
> > I completed the refurbishing of this amplifier.
> >
> > Best 73s, and happy testing/tuning.
> >
> > Bill W7EXG
> >
> > ______________________________________________________________
> >
>
> ______________________________________________________________
> SADXA Website http://www.sadxa.org
>
> SADXA mailing list
> Home: http://mailman.qth.net/mailman/listinfo/sadxa
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:SADXA at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> You can support qsl.net: http://www.qsl.net/donate.html