"Max Power" wrote in message
...
AM radio multiplexing question: transmitting SSB in sync with AM (numbers
stations, clandestine broadcasting)

I understand that it is possible to multiplex SSB transmissions on top of
AM
transmissions, especially on SW.
The AM transmission is decoded by the envelope or PLL coherer, the SSB
transmission is ignored.

SSB is a form of amplitude modulation. SSB is just one sideband of a
standard AM signal, without the carrier.



On a properly tuned SSB receiver, the AM transmission only partially
interferes with the SSB transmission.

If a SSB and standard AM signal are sharing the the same frequencies, they
will interfere with each other.



Some numbers stations use this transmission technique, but it just as
valid
if say Radio Free Asia were to use this technique by transmitting over
Chinese domestic radio.


Huh? Is this supposed to be some sort of scheme for getting propaganda
broadcasts into China? How many Chinese own these imagined fancy radios?

Which numbers stations use this technique?



1. What is the math behind this transmission working (SSB is a form of
Angle
Modulation, not Amplitude Modulation)?

Single Sideband IS amplitude modulation. One of the AM stereo methods used
independent sidebands for each channel. This was purely amplitude
modulation. Other methods used phase modulation.

The Radio Amateur's Handbook has a good description of the various forms of
amplitude modulation and frequency/phase modulation. There may be a copy at
your local public library.

There's a few websites about AM stereo modulation.



2. Are some receivers more affected by (interference where) SSB
transmissions superimposed over AM than others? (PLL versus SYNC vs
Envelope
Detectors)


AM interferes with SSB and vice-versa. If there were ways to seperate them,
then radio amateurs would use those ways. As it is, some SSBers are annoyed
by AMers because AM uses twice the bandwidth as SSB, as well as throwing a
big heterodyning carrier into the mix.

Frank Dresser