"Stefan Wolfe" wrote in
:

My MFJ tuner has a scale called "Average Power", along with "PEP".
Gosh, if my MFJ tuner has it on the dial, it exists! :-))

Well, you would believe anything.

Some MFJ tuners that have a PEP switch do not read PEP reasonably
accurately on speech. Some of them that don't work (eg 949E) have a place
on the board for the transistor amplifier that is incorporated in other
models, and they can be fixed by adding the 10 cent transistor and one or
two other parts... but it is a huge job to get the PCB out of the tuner
to do the work.

The 'Average Power' reading might be reasonably accurate on an
unmodulated carrier, but it is certainly not on a complex waveform like
speech, and is another example of MFJ's labelling. In the so-called
'average power' mode, the circuit is a half wave peak responding RF
detector with a short (wrt speech) decay time constant driving a
D'Arsonval meter movement which responds to the average current where the
current is proportional to square root of power under constant carrier.

The BS in the 'average power' story is revealed by measuring the average
power of a Morse transmitter sending continuous dits with 50% duty
cycle... the 'average power' reading instruments are unlikely to read 50%
of the key down power, and the reading is likely to vary significantly
with dit speed.

A similar experiment will reveal the failure of some of the MFJ PEP power
meters to correctly indicate PEP on the Morse waveform.

Owen