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I've been working on a system to accurately evaluate HF linear power amplifiers.? It took quite a while to figure out how to get the system working.
Here's the first tangible results in the form of a spreadsheet:

There are 3 worksheets.? The first "PA out cal" is nothing more than measurements between reference plane 1 (PA output), reference plane 2 (radio output), and the input of the power meter.

Sheet #2 is the "Small Balun" version of the T41-2 Power Amplifier (final + driver).? Sheet #3 is the K9HZ amplifier I built here a couple of years ago.

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PEP output powers are not as high as expected.? Remember to halve the PEP numbers to get average power.? Quite low!

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Note that the K9HZ PA drops to below 2 watts average power on the higher bands.? The amplifier was tuned up according to the build instructions.

The critical thing seems to be the bias current for the final transistors is probably too low at 250mA each.

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I've seen comments by others that the part used in the final amplifier (Mitsubishi RD16HFF1) needs quite a bit of quiescent bias current for decent linearity.

Thus I've tuned the T41-2 Power Amplifier to a bias of 700mA each.? You can see the total current drain in the last column of the measurements.

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I would be interested to compare my measurements to other's evaluations.? Here is a video summary of the measurement system and procedure:

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The system:

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The measurement procedure:

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73 Greg KF5N

Good work Greg!

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I would like to perform this test on my 25W Power Amplifier, does version 66.9 of the code have this IMD test?

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73 John G0SDF

Hi John-

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I'm not sure what is in V66.9.? I was using an unpublished branch of T41EEE.9.

The branch is here:

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The test is in SSB Options.? The usual adjustment encoder increases the level of the two tones.

This is experimental code!? ?At least in my radio it worked quite smoothly, however, I intend

to do more testing before release in the next version of T41EEE.

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73 Greg KF5N

Thanks Greg for your clear description of the measurement systems you are using to evaluate available RF power amplifiers suitable for use with the T41 and other equipment.

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As your videos confirm, it is essential that any quoted measurements and specifications are as accurate and understandable as possible.? Your videos and results suggest that the actual performance of some amplifiers falls well below their claimed specifications.

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You have explained qualifiers? such as Average Power, Peak Power, PEP and others which is very helpful.? ?

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We may call ourselves “Radio Amateurs” or “Hams” but we should ?still be bound by the professional unit standards which we accept and respect.?? For power, the standard unit is the “Watt” and a common definition is based on the heating effect of the power applied to an object such as a dummy load or an aerial.? The “power applied to an object” may be driven by mechanical energy, electrical energy or other forms of energy.

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On one occasion when I doubted my shack RF power meter, I placed my dummy load in a well insulated bath of water and noted the rate of rise of temperature.? After some measurements and calculations, I was re-assured that my RF power meter was? in the right ball park.

My point is that if something is referred to as a 10, 20, 50 or whatever Watt amplifier then that is the minimum it must deliver and there should be no ambiguity in the meaning of any values quoted.

Harry? GM3RVL