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

[kd6xh at comcast.net]

My mind and activity has not done well.  I forgot to put in in my calendar.  That is the problem. 

----- Original Message -----

From: "Jerry Wothe" <jdwothe at cox.net> 
To: "Southern AZ DX Association E-Mail Reflector" <sadxa at mailman.qth.net> 
Sent: Thursday, March 17, 2016 8:22:36 AM 
Subject: Re: [SADXA] PEP vs N Tone Average Power - Amplifier Tuning 

Tis  the third Thursday of the month, it hasn't changed in may years. 

On 3/17/2016 8:06 AM, kd6xh at comcast.net wrote: 
> Am I right in assuming that the club meeting is tonight?  If so, I plan to attend. 
>     
> KD6XH 
> 
> ----- Original Message ----- 
> 
> From: "Wes (N7WS)" <wes at triconet.org> 
> To: sadxa at mailman.qth.net 
> Sent: Wednesday, March 16, 2016 1:57:51 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 
>> 
>> ______________________________________________________________ 
>> 
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