In article ,
"Ron Baker, Pluralitas!" wrote:

"isw" wrote in message
...
In article ,
"Ron Baker, Pluralitas!" wrote:

"John Fields" wrote in message
...
On Thu, 5 Jul 2007 00:00:45 -0700, "Ron Baker, Pluralitas!"

snip


When AM is correctly accomplished (a single voiceband signal is
modulated

The questions I posed were not about AM. The
subject could have been viewed as DSB but that
wasn't the specific intent either.

What was the subject of your question?

Copying from my original post:

Suppose you have a 1 MHz sine wave whose amplitude
is multiplied by a 0.1 MHz sine wave.
What would it look like on an oscilloscope?
What would it look like on a spectrum analyzer?

Then suppose you have a 1.1 MHz sine wave added
to a 0.9 MHz sine wave.
What would that look like on an oscilloscope?
What would that look like on a spectrum analyzer?

---
The first example is amplitude modulation precisely _because_ of the

Is there multiplication in DSB? (double sideband)

Yes, and in fact, that multiplication referred to above creates a
DSB-suppressed-carrier signal. To get "real" AM, you need to add back
the carrier *at the proper phase*.

So does the multiplication in the first example really make
it amplitude modulation?

Yes, because the output signal varies in amplitude with modulation. For
suppressed carrier SSB or DSB, the output is zero when there's no
modulating signal, while for "traditional AM", the output is 50% for no
modulation.

Compare to FM or PM, where the output is constant regardless of the
modulation level. True, FM has a lot of sidebands that vary in
amplitude, but if you add them all together, the output is constant.

Run an SSB, DSB, or AM rig into a dummy load and it'll get hotter with
modulation, while with FM the temperature won't change.

--

But recall that if you take that DSB signal you got by multiplication,
and reinject the carrier in quadrature, you no longer have amplitude
modulation.

Isaac