On a sunny day (Tue, 13 Jun 2006 00:32:38 GMT) it happened james
wrote in :

A product Detector is prefered due to its mixer characteristics. Being
balanced, the two inputs are supressed sufficiently to make filtering
their components in the output much easier. Product detectors and
Envelope dection is not the only means of detecting DSB-SC and DSB-LC
signals. They are the most simplest and easiest to implement.

I have used sampling to demodulate QAM, In any color TV you will find it,
carrier is regenerated in phase from the color burst, look up NTSC.
And there we have 2 modulating systems, here is how that works in the
time domain:
http://groups.google.com/group/sci.e...ce23fcbb253646

The main thing is perhaps that you can see that in SSB, if we have 1MHz
carrier, and 1kHz sine modulation, we get a 1.001 MHz carrier (or 0.999 if
the other sideband is used.
So to get the original back, it would be sufficient to substract the 1MHz
again in the first case (1.001 - 1) = 1kHz, or in the other case 1 - .999.

In the DSB-SC case we would have 1.001 AND .999 AT THE SAME TIME.

Using one sideband is enough. DSB uses double the bandwidth and as such
is less efficient then SSB,

Distortion of the RF waveform may not nescessarily indicate that the
detected audio is unintelligable. As long as the recovered audio is
reproduced accuarately during demodulation then there is no
distortion.

But it won't [work].
What the 4 diode ring modulator does, is make a RF amplitude phase phi
when the audio signal goes positive proportional to the audio amplitude,
and the same with phase phi+180 degrees when the audio signal goes negative.
If you do AM envelope detector (as the you normally do with a diode and RC
lowpass) you get a wave form that is no longer a sine, but looks like double
phase rectified sine when filtered.


Spectral content of the demodualted signal can be set by
post detection filtering. This can reduce to some extent the harmonics
of the modulating signal.



By the way the lab you point to is more about the generation of a DSB
signal. From figure 4 you are making statements about demodulation.

Of course, lok at that waveform, build a 'non distorting AM detector
for it without carrier re-insertion (BFO, some oscillator), you CANNOT.
Modulation /demodulation is related.

Please build one, try it,

Since the information in both sidebands are indentical the only need
for the second sideband is to increase demodulated audio.

Yes, we agree here.

Please try it:

But for the non-believers, try it out, all you need is an audio amp,
oscillator, 4 diodes, and of course a 27 HHz xtal oscillator.
http://www.nzart.org.nz/nzart/examin...les/Mixers.htm
There is a description and diagram a bit down on the page.

Listen to it on an AM receiver, and you will KNOW.