Radium hath wroth:

On Jun 30, 3:46 pm, Jeff Liebermann wrote:

With AM, it's ALWAYS the high frequency
that acts as the carrier
and the lower that acts as the modulation.

In AM, isn't the carrier the signal which always maintains a constant
frequency and only varies by amplitude?

You really are clueless. 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. You could have two
modulators in series, that would make the circuit overly complicated.
Please re-read my highly simplified previous explanation about the
symmetry of the AM multiplier (mixer) input ports until it's absorbed
and understood by your porous brain.

Incidentally, the reason I keep using the term "multiplier (mixer)" is
to avoid confusion with a harmonic multiplier. An AM modulator is a
mixer, not a harmonic multiplier.

Also, the carrier might remain constant frequency, for a given FCC
channel assignment, but the modulation is all over the place. For
example, your voice goes from 300 to 3000Hz, all of which is fed to
the modulator for digestion.

Conventional TV is VSB (visidual side band) which is a form of AM with
one of the two side bands partially removed, usually by filtering.
There's a carrier 1.25MHz offset for the video, another carrier 4.5Mhz
offset for the audio, and whatever else they can throw in for low
speed data. Two more more carriers are required for TV+audio.

If you want to get really high-techy, the new digital modes (DRM,
iBiquity, HD Radio, etc) all have multiple carriers, each of which is
modulated individually. Same with various OFDM modes, which have
multiple carriers, individually modulated and positioned orthogonally
from each other to prevent mutual interference from adjacent modulated
carriers.

If a carrier signal varies by anything other than just amplitude, then
it isn't AM. Right?

Wrong. The carrier can also vary, such as in a sweep generator or
jammer. It's not commonly done but it's possible. Want to obliterate
the entire AM broadcast band? No problem. Just sweep the carrier
from 530KHz to 1650KHz, while modulating the 300 to 3000Hz audio with
a rendition of your incoherent ranting.

By the way, you're welcome.


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

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.

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. This is not true. 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.

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.

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.]

On 6/30/07 8:01 PM, in article
, "Radium"
wrote:

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.

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. This is not true. 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.

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.

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.]


You should just recall that post.

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

On 6/30/07 7:43 PM, in article ,
"Jeff Liebermann" wrote:

Radium hath wroth:

On Jun 30, 3:46 pm, Jeff Liebermann wrote:

With AM, it's ALWAYS the high frequency
that acts as the carrier
and the lower that acts as the modulation.

In AM, isn't the carrier the signal which always maintains a constant
frequency and only varies by amplitude?

You really are clueless. 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. You could have two
modulators in series, that would make the circuit overly complicated.
Please re-read my highly simplified previous explanation about the
symmetry of the AM multiplier (mixer) input ports until it's absorbed
and understood by your porous brain.

Incidentally, the reason I keep using the term "multiplier (mixer)" is
to avoid confusion with a harmonic multiplier. An AM modulator is a
mixer, not a harmonic multiplier.

Also, the carrier might remain constant frequency, for a given FCC
channel assignment, but the modulation is all over the place. For
example, your voice goes from 300 to 3000Hz, all of which is fed to
the modulator for digestion.

Conventional TV is VSB (visidual side band) which is a form of AM with
one of the two side bands partially removed, usually by filtering.
There's a carrier 1.25MHz offset for the video, another carrier 4.5Mhz
offset for the audio, and whatever else they can throw in for low
speed data. Two more more carriers are required for TV+audio.

If you want to get really high-techy, the new digital modes (DRM,
iBiquity, HD Radio, etc) all have multiple carriers, each of which is
modulated individually. Same with various OFDM modes, which have
multiple carriers, individually modulated and positioned orthogonally
from each other to prevent mutual interference from adjacent modulated
carriers.

If a carrier signal varies by anything other than just amplitude, then
it isn't AM. Right?

Wrong. The carrier can also vary, such as in a sweep generator or
jammer. It's not commonly done but it's possible. Want to obliterate
the entire AM broadcast band? No problem. Just sweep the carrier
from 530KHz to 1650KHz, while modulating the 300 to 3000Hz audio with
a rendition of your incoherent ranting.

By the way, you're welcome.



You are getting far afield of classical AM, which is the subject of Radium's
post. He is confused and you aren't helping.

Jeff Liebermann wrote:

Conventional TV is VSB (visidual side band)


Vestigal Sideband


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

In message , Michael A. Terrell
writes
Jeff Liebermann wrote:

Conventional TV is VSB (visidual side band)


Vestigal Sideband


Better still, Vestigial Sideband!
--
Ian

On Mon, 2 Jul 2007 16:41:01 +0100, Ian Jackson wrote:
In message , Michael A. Terrell
writes
Jeff Liebermann wrote:

Conventional TV is VSB (visidual side band)


Vestigal Sideband


Better still, Vestigial Sideband!

You're both wrong. It is VIRTUAL SIDEBAND because it isn't completely
real and the other sideband which isn't virtual carries the missing high
frequency modulation info. Once it gets into your second detector then
it becomes real due to the laws of product modulation.

Next, you will be telling people that VGA doesn't stand for "virtual
graphics array."

--
Posted via a free Usenet account from http://www.tarrnews.net

" wrote in message
...
Better still, Vestigial Sideband!

You're both wrong. It is VIRTUAL SIDEBAND

Nope - VSB, as commonly used in broadcast television,
most definitely stands for "vestigial sideband" - a form of
AM in which the carrier and part of one sideband (in this
case, the lower sideband is the "vestigial" one) are retained,
along with one full sideband which carries the information
(in this case, the upper sideband, which carries the luminance
(Y) video information).

Bob M.

On Mon, 2 Jul 2007 17:08:43 -0600, "Bob Myers"
wrote:


" wrote in message
...
Better still, Vestigial Sideband!

You're both wrong. It is VIRTUAL SIDEBAND

Nope - VSB, as commonly used in broadcast television,
most definitely stands for "vestigial sideband" - a form of
AM in which the carrier and part of one sideband (in this
case, the lower sideband is the "vestigial" one) are retained,
along with one full sideband which carries the information
(in this case, the upper sideband, which carries the luminance
(Y) video information).

Bob M.

It is definitely vestigial side band. There is a bandpass filter in
transmitter to get rid of much of it when the signal is generated, and
generally a tuned coaxial stub on the antenna to get rid most of the
rest of it.

Effectively NTSC television is single sideband with carrrier (while
SSB is technicall SSBSC, Single Side Band, Supressed Carrier, which is
considerably more difficult to generate and detect).