On Sep 15, 10:05 pm, "Brenda Ann" wrote:
"craigm" wrote in message

...

The detector in your basic AM radio is much the same as it has been for
nearly 100 years now. It rectifies one half of the envelope and filters
out
the remaining RF to leave an audio waveform. It does not detect both
halves (both sidebands) of the waveform. This is why such things as
selectable
sideband make high end radios better able to pick out a signal. The
signal with both sidebands may be applied to the detector, but it's not
what comes out. I stand by my question. If only one sideband is actually
detected, there can be no phase cancellation.

You clearly don't understand how an AM detector works.

But I do. The basic AM detector works exactly as any half-wave rectifier. If
you used a full-wave rectification, then you could detect both sides of the
RF waveform, but logic would seem to dictate that this would cancel the
audio waveform, since the two sidebands are mirror images of one another.

You are mistaken in thinking that the positive and negative sides of
the RF envelope correspond to the upper and lower sidebands. They do
not. Examine a SSB envelope - it has positive and negative components
that must balance each other, else there would be a DC component. How
could DC be delivered through a vacuum? It is correct that applying
modulation to one side of an Independent Sideband transmitter and anti-
phase modulation to the other side will result in cancellation in the
envelope detector, whether it is half-wave or full-wave, provided both
sidebands are delivered equally. If one sideband is cut off (by
filtering in the receiver), then there would be no cancellation. For
normal DSB-AM, the two sidebands are modulated in phase and the
envelope will be detected by both half-wave and full-wave.detectors,
whether one sideband or both are passed to the detector with carrier.

Regards,
Tom