I have some ideas, but that's all. I hope someone with more recent
direct experience with AM broadcasting than mine who really knows the
answer will comment.

I will go out on a limb and speculate that the carrier isn't being
reduced during modulation. If it were, simple envelope detectors would
produce serious distortion. And if the carrier isn't being reduced, then
the power has to be greater when modulation is present. But let's see if
an expert will comment -- if I'm wrong I'll gladly eat my words.

Roy Lewallen, W7EL

Bill Turner wrote:


Last year I took a tour of the KFI transmitter site in Southern
California and was fascinated by the 50kW transmitter. On the
transmitter's front panel was a meter calibrated in output power. It
read *steady* at 50kW, except when the operator dropped the power
momentarily to 5kW, just to show he could.

Ever since then, I've kicked myself for not asking why the power didn't
rise with modulation. The transmitter was a Harris model DX50 (IIRC)
which uses dozens of low power solid state modules which are switched on
and off digitally to produce the RF output. Could it be that as they
are switched on and off, they also are driven in such a way as to
maintain constant power? In other words, when modulation is added the
carrier power is reduced? It's the only thing that comes to mind, but
there may be another reason.

Ideas?

--
Bill W6WRT