[AMRadio] The Physical Reality of Sidebands in the AM signal


Donald Chester k4kyv at charter.net
Wed Oct 5 13:31:28 EDT 2016


> I should say also that the phasing products are also not present in the
three
> transmitter imaginary scenario but are generated within the receiver to
give
> the appearance of an AM signal.

John,

That will take some head scratching. The last time I remember contemplating
it was in Houston, the time you and I were at some Mexican restaurant (or
was it a honky-tonk?), we were discussing synchronous detectors, and I drew
out some vector phasing diagrams on a paper napkin.  Remember that?

Anyway, it's a good question.  Say you had a high-level balanced modulator
for a DSB generator and you mixed in a  carrier and combined the outputs to
generate an AM signal. Now add an  rf phase shift network somewhere between
the carrier oscillator and the final, and adjust the coil and capacitor to
rotate the phase of the carrier 90 degrees. Now, you come out with a phase
modulated carrier, with no amplitude modulation and therefore no net
increase in average power when modulation is applied.  Where is all that
audio power going?


Don k4kyv



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