B
boki
- Jan 1, 1970
- 0
What is modulator?
boki said:What is modulator?
boki said:What is modulator?
niftydog posted, in part:
<< In AM (amplitude modulation) the carriers AMPLITUDE varies in
proportion to the audio signal. >>
In AM modulation, the carrier amplitude does NOT vary - it is constant. The
process of modulation produces sidebands.
Steve said:[email protected] (Dbowey) wrote in message
I understand, but given the broken english in the OPs question I was
trying to give as simple an answer as possible so they might glean the
basic concept. I can appreciate how my statement would have misled
people.
Looking at a simple AM envelope on a CRO gives a beginner the
impression that the amplitude is changing in proportion to the
message.
Dbowey said:Kevin posted much irrelevant STUFF, but I choose to comment on the
following: << The peak to peak amplitude of the complete signal
is indeed changing. Thats what AM means. Sure, you can make an
argument that the signal is composed of different components or
"signals" in the frequency domain, only some of which has changing
amplitudes, but in the time domain, there is only one "signal", i.e
the one voltage/current at any instant of time.
Sure, if we ignore that a scope is essentially a not-very-smart AC
voltmeter, we might be satisfied that we have the entire answer.
That's what AM means? I believe the first guys that modulated an
oscillator and heard the result on their diode detector did think the
ampltude of the carrier varied and "Amplitude Modulation" was a
descriptive term at the time.
It doesn't mean we should wear blinders
and ignore the realities of the frequency domain view.
Today there are many ways to observe that the sidebands are separate
from the carrier, and one does not require a spectrum analyzer to do
this.
<< The frequency in absence of any modulation frequency",
seems a bit much. >>
What's the problem? A frequency in absence of any modulation is
simply an unmodulated signal; a "carrier" awaiting modulation or a
signal waiting to be keyed to send code.
Dbowey said:Kevin posted much irrelevant STUFF, but I choose to comment on the
following: << The peak to peak amplitude of the complete signal
is indeed changing. Thats what AM means. Sure, you can make an
argument that the signal is composed of different components or
"signals" in the frequency domain, only some of which has changing
amplitudes, but in the time domain, there is only one "signal", i.e
the one voltage/current at any instant of time.
Sure, if we ignore that a scope is essentially a not-very-smart AC
voltmeter, we might be satisfied that we have the entire answer.
That's what AM means? I believe the first guys that modulated an
oscillator and heard the result on their diode detector did think the
ampltude of the carrier varied and "Amplitude Modulation" was a
descriptive term at the time.
It doesn't mean we should wear blinders
and ignore the realities of the frequency domain view.
Today there are many ways to observe that the sidebands are separate
from the carrier, and one does not require a spectrum analyzer to do
this.
<< The frequency in absence of any modulation frequency",
seems a bit much. >>
What's the problem? A frequency in absence of any modulation is
simply an unmodulated signal; a "carrier" awaiting modulation or a
signal waiting to be keyed to send code.
Dbowey said:Kevin posted much irrelevant STUFF, but I choose to comment on the
following: << The peak to peak amplitude of the complete signal
is indeed changing. Thats what AM means. Sure, you can make an
argument that the signal is composed of different components or
"signals" in the frequency domain, only some of which has changing
amplitudes, but in the time domain, there is only one "signal", i.e
the one voltage/current at any instant of time.
Sure, if we ignore that a scope is essentially a not-very-smart AC
voltmeter, we might be satisfied that we have the entire answer.
That's what AM means? I believe the first guys that modulated an
oscillator and heard the result on their diode detector did think the
ampltude of the carrier varied and "Amplitude Modulation" was a
descriptive term at the time.
It doesn't mean we should wear blinders
and ignore the realities of the frequency domain view.
Today there are many ways to observe that the sidebands are separate
from the carrier, and one does not require a spectrum analyzer to do
this.
<< The frequency in absence of any modulation frequency",
seems a bit much. >>
What's the problem? A frequency in absence of any modulation is
simply an unmodulated signal; a "carrier" awaiting modulation or a
signal waiting to be keyed to send code.
Dbowey said:Kevin [wrote]The peak to peak amplitude of the complete signal is
indeed changing. Thats what AM means. Sure, you can make
an argument that the signal is composed of different
components or "signals" in the frequency domain [...]
[...] That's what AM means? I believe the first guys that
modulated an oscillator and heard the result on their
diode detector did think the ampltude of the carrier
varied and "Amplitude Modulation" was a descriptive term
at the time. It doesn't mean we should wear blinders and
ignore the realities of the frequency domain view.
Jim said:Dbowey said:Kevin [wrote]The peak to peak amplitude of the complete signal is
indeed changing. Thats what AM means. Sure, you can make
an argument that the signal is composed of different
components or "signals" in the frequency domain [...][...] That's what AM means? I believe the first guys that
modulated an oscillator and heard the result on their
diode detector did think the ampltude of the carrier
varied and "Amplitude Modulation" was a descriptive term
at the time. It doesn't mean we should wear blinders and
ignore the realities of the frequency domain view.
Guess what guys, you're both right.
The time-domain
explanation and the frequency domain explanation are equally
valid.
That's what AM means? I believe the first guys that modulated an oscillator
and heard the result on their diode detector did think the ampltude of the
carrier varied and "Amplitude Modulation" was a descriptive term at the time.
John Fields posted:
Never mind.... it didn't add anything to the discussion.
The biggest problem with the simple 'Fourier' view of a timeKevin said:Jim said:Dbowey said:Kevin [wrote]
The peak to peak amplitude of the complete signal is
indeed changing. Thats what AM means. Sure, you can make
an argument that the signal is composed of different
components or "signals" in the frequency domain [...][...] That's what AM means? I believe the first guys that
modulated an oscillator and heard the result on their
diode detector did think the ampltude of the carrier
varied and "Amplitude Modulation" was a descriptive term
at the time. It doesn't mean we should wear blinders and
ignore the realities of the frequency domain view.
Guess what guys, you're both right.
Err..I know...That's exactly what I said, ho..humm....
The time-domain
explanation and the frequency domain explanation are equally
valid.
That's right, and there's more. There is no unique way of describing the
universe. I expanded on this in a follow-up post, which, for some
reason, has appeared 3 times.
A point here is that the Fourier view of the universe in EE is so
abundant, that to see things in any other way needs a paradigm shift.
[/QUOTE][/QUOTE]< On 18 Sep 2003 16:15:44 GMT said:John Fields posted:
Never mind.... it didn't add anything to the discussion.
dyson said:The biggest problem with the simple 'Fourier' view of a timeKevin said:Jim said:Dbowey wrote:
Kevin [wrote]
The peak to peak amplitude of the complete signal is
indeed changing. Thats what AM means. Sure, you can make
an argument that the signal is composed of different
components or "signals" in the frequency domain [...]
[...] That's what AM means? I believe the first guys that
modulated an oscillator and heard the result on their
diode detector did think the ampltude of the carrier
varied and "Amplitude Modulation" was a descriptive term
at the time. It doesn't mean we should wear blinders and
ignore the realities of the frequency domain view.
Guess what guys, you're both right.
Err..I know...That's exactly what I said, ho..humm....
The time-domain
explanation and the frequency domain explanation are equally
valid.
That's right, and there's more. There is no unique way of describing
the universe. I expanded on this in a follow-up post, which, for some
reason, has appeared 3 times.
A point here is that the Fourier view of the universe in EE is so
abundant, that to see things in any other way needs a paradigm shift.
varying amplitude modulation is that the Fourier view changes
in character (and cannot directly describe the f(t) AM process.)
If everything is constant, then the Fourier view can make some
sense.
I agree with you that either the f(t), f(w) or whatever views
are equivalent, but f(w) becomes quite complex when the f(t)
signals aren't constant in character. It is best to keep full
understanding of the various processes, and decide when the f(w)
view is the best way of viewing things, and when the f(t) way
is good.
In the more general case, f(t) will help to solve problems that
f(w) will give LOTS of trouble -- but the f(w) is a good set of
shortcuts.
I agree with Kevin, that in the steady state, f(w) and f(t) can
be equivalent.