On a sunny day (Tue, 13 Jun 2006 00:44:15 GMT) it happened james
wrote in :

On 12 Jun 2006 13:42:26 -0700, "Telstar Electronics"
wrote:

+++So let me get this straight... In DSB-SC... both sidebands are
+++transmitted... but there is no carrier sent at all? Correct?... and the
+++carrier is re-inserted at the receiver.
+++
*************

Not exactly. Supressed carrier is just that. The carrier is suppressed
by a desired amount measured in dBs. It can be fully suppressed or
partially supressed.

+++Now with the swing set-up... both sidebands are transmitted... along
+++with the carrier... but the carrier's amplitude changes from extremely
+++low to a normal AM carrier when the modulation is added.
+++
*************

There is several techniques that has been used in amatuer radio for
many decades. One stems from the old tube days called grid modulation.
What happens here is that the modulated stage, usually the final RF
stage, has the modulation signal applied to the grid of the tube. By
varying the grid voltage at an audio rate, the bias on the tube
varies. This will change the gain of the tube. What happens then is
when there is no modulation signal the tube is at or near cutoff and
there is little carrier. As you modulate the carrier varies at an
audio rate. Disadvantage of this method is the maximum percentage of
modulation is about 85%.

Another method is one sed by the Drake 4 line series of transmitters.
This is where modulation is applied to a low level stage. Usually a
balanced modulator. To achieve AM, the balanced modulator is slightly
kicked off balanced to allow a small amount of carrier to appear at
the output. With modualtion this will vary some. Subsequent stages of
amplification will bring the signal up to the desired level.

james

100% agreed.