Radium hath wroth:

On Jun 30, 7:43 pm, Jeff Liebermann wrote:

The carrier does NOT vary in amplitude. If
it did, that would be modulating the carrier, which is the job of the
modulator, not whatever is producing the carrier.

Exactly. The modulator signal modulates the carrier wave. If there is
no modulator signal, then the carrier does not vary by amplitude or by
anything.

Brilliant. Yes, if there is no signal input, there's no change in
output.

Incidentally, in an AM system, the carrier does NOT change. You can
see that on a spectrum analyzer. Modulate all you want and the
carrier stays put at 50% of the total power output. The rest of the
power is split between the upper and lower side bands. If there is no
modulation input, then the side bands disappear, but the carrier just
stays there.

As someone mentioned, there is usually some residual FM on the carrier
usually caused by sloppy power supply regulation. Also, some
synthesizer noise. A well designed AM broadcast transmitter doesn't
have much of this junk present. The problem is that the FM that
appears on the carrier also appears on all the side bands. It doesn't
hurt if the carrier has a little residual FM, but any such junk on the
sidebands will result in a substantial increase in audible noise by
mixing with the audio.

One poster stated that the signal with the higher-frequency is
automatically the carrier wave while the signal with the lower-
frequency is automatically the modulator wave.

That was me.

This is not true.

Prove it. I explained how it works and why quite adequately. I
didn't even need to resort to formulas and calculations. The
multiplier (mixer) modulator inputs are symmetrical and identical.
Therefore the inputs are also symmetrical and indistinguishable. I
also provided a simple audio test you can do in your spare time to
demonstrate how it works.

Now, convince me that the multiplier (mixer) waveform would be
different depending on which input was the carrier or modulation.

What
I was trying to say is that an AM radio carrier wave cannot vary
significantly by anything other than its amplitude [though, as one
poster pointed out, the AM carrier can experience extremely-negligible
variations in frequency]. If an AM radio signal has that restriction,
it is the carrier wave. If an AM radio signal does not have that
restriction, then it is the modulator wave. This is true, even if the
AM carrier wave is of a lower-frequency than the modulator wave.
That's what I was trying to say.

I give up. What you've done is created a word salad. That's where
you have a mess of buzzwords, shredded together, mixed with some
window dressing, and served in a manner to imply that you have a clue
what you're disgorging. Even the most basic concepts are not sinking
in. You've also ignored multiple suggestions to read some very fine
sources on how RF and modulation works. Open book, insert face, and
come back when you have a clue as to the basics.

In AM radio, determining which is the carrier wave and which is the
modulator wave is not by which has the higher frequency but rather by
which has the restriction that I stated.

Wrong. With AM it's easy. The higher frequency is always the
carrier. Can you give me a diagram or a commonly used communications
system where the reverse might be true? I can't.

If there is no modulator signal, then no carrier signal of any type
[AM, FM, etc.] will vary by any quality [frequency, amplitude, phase,
etc.]

Yawn...

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558