I still have trouble visualizing how a 180 or 270 degree change can occur
in a
single rf cycle and be able to overcome the "inertia" (probably a
poor choice of words) of the rf circuits , feed line and antenna
system.

Gary
W4AF


Gary:

For the phase shift to occur during one RF cycle, wouldn't that suggest that
the modulating frequency is close or equal to the RF carrier frequency? I
don't think that is the situation you are trying to visualize. The
modulating frequency, in voice or common digital modes, is more likely a
tiny fraction of the RF carrier frequency. The phase shift of the RF
carrier only has to occur at the modulating freqency, not at the RF
frequency. That means that during the modulating phase shift, many
thousands or even millions of RF cycles can occur.

If you are thinking of a mode like PSK 31, in which modulation is by phase
shift, remember that the phase shift occurs in the audio tone that is
modulating the RF signal. The RF signal can follow this phase change
easily, since many millions of RF cycles occur during the audio phase shift.

Roger K6XQ