[Boatanchors] SSB and carrier insertion?

[Brian Clarke]

Hi Gary,

That's really intriguing. Have you a reference for any of this material? I have 
been teaching broadcast engineering for some years and I've not heard any 
of this before - I'ld like to put it in front of my aspiring broadcast engineers.

What kind of AM detector uses both the upper and lower envelopes 
simultaneously?  

I suspect that the lack of punch, another quaint 'technical term', may be 
more related to the lack of bass which comes with trying to achieve a filter 
with steep sides that only responds to one sideband. A normal AM 
detector can go right down to near DC if required.

What is there in the detection process that gives rise to more distortion 
with one kind of signal than another? I assume you mean waveform [ie, 
amplitude vs time] distortion rather than frequency or phase distortion.

And 6 dB carrier reduction - compared with what? And audio peak power 
6 dB higher than the carrier in normal AM - now let me see if I understand 
that - if I have a DSBAM transmitter with a 100 W carrier, then I must have 
400 W of audio peak power - so, as it's DSB, I would have 200 W per 
side. Silly me - I always thought that I required only 50 W total for the two 
sidebands for 100 % modulation. I wonder if Fred Terman ever saw the 
maths for that one?

All very intriguing.

73 de Brian, VK2GCE.
  Gary said:

  SSB AM does not have quite the audio punch that full AM does. Without 
  the other side band the detected audio at the receiver is 6 db down from 
  what a double side band AM signal would be. There is 3 db less audio 
  power being transmitted and the detector has another 3 db of loss not 
  having the coherent other side band present to add in the detector.

  The detector in the receiver will also have more distortion as 
  modulation approaches 100% with single side band AM from what it will 
  with double side band AM. This is why it sounds a little funny compared 
  to full AM. In essence the detector gets confused as to whether the 
  audio is modulating the carrier or the carrier is modulating the audio 
  signal.

  When operating SSB with carrier or double side band with carrier, with a 
  side band transmitter the carrier needs to be reduced 6 db in order for 
  it to operate properly. This allows the amplifier in the transmitter to 
  achieve the peaks of the audio power.

  A normal AM transmitter has audio peak power 6 db higher than the 
  carrier (4 times the power)