The topic has many more nuances than that graphic depicts. You are correct from a license question perspective but not from a true application perspective.

The general tendency to use sine wave conversion factors for an amateur radio transmitter or linear is not well founded. Most of our amplifier stages are class AB through class C depending on the mode. These stages do not deliver a sine wave as the carrier so using the sine wave relationships is only an approximation. There can be significant errors in this assumption. The good news is that the errors make the calculated P.E.P overly conservative.

As an example of the potential error, consider using an oscilloscope and measuring the peak voltage of a CW transmitter at 100 volts into a 50+j0 ohm load. If the carrier is a true sine wave, we would calculate P.E.P as:

P.E.P. = (100 * 0.707)

^{2}/50 = 100 watts P.E.P.

However, a class C amplifier has only an ~50% conduction angle. Assuming the original wave that is amplified by this class C amplifier is a pure sine wave, then we would calculate P.E.P. as:

P.E.P. = (100 * 0.51)

^{2}/50 = 52 watts P.E.P.

Why is this the case? For one half of the original sine wave, the amplifier output remains at 0 watts (and thus 0 volts). When it reaches 1/2π radians, it begins to follow the exciting sine wave times the gain of the amplifier. When the sine wave reaches 1.5π radians, there again is no output from the amplifier. The definition of P.E.P. is the

*average* power supplied to the antenna transmission line by the transmitter during one RF cycle at the crest of the modulation envelope, under normal operating conditions. The normal 0.707 multiplier assumes that the full sine wave is present but in this case it is not. So the RMS conversion factor must necessarily be reduced since the full sine wave is not present.

Often the output circuit of the amplifier will tend to smooth out some of the output waveform so the conversion factor will not be as extreme but the general principal applies.

The same can be applied for a typical class AB amplifier with a greater conduction angle - only in this case, the RMS factor will be much closer to 0.707.

The formula referenced for the license exams is basically assuming a no distortion, class A amplifier which is hardly ever used in amateur applications due to its inefficiency.

- Glenn W9IQ