audio recording on IC -help wanted

[Brian Gregory [UK]]

"Green Xenon [Radium]" <glucegen1@excite.com> wrote in message
news:46f6f08e$0$16535$4c368faf@roadrunner.com...

Would using Quadrature Frequency Modulation be of any help?

Quadrature Amplitude Modulation uses a combo of AM and Phase-Shift-Keying.

So QFM would use a combination of FM and PSK. Would this decrease the
bandwidth required for broadcasting FM luminance video signals?

Think about it.
Obviously there is no way FM and PSK can be going on at the same time in any
way that can convey separate information. Worse still if you separately FM
modulate two signals that start in quadrature with each other they won't
stay in quadrature.

--

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.

 

[Brendan Gillatt]

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Green Xenon [Radium] wrote:

On Sep 23, 3:02 pm, Brendan Gillatt
brendanREMOVET...@brendanREMOVETHISgillatt.co.uk> wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/4c903b0a453a39fa :

Okay now you're actualy irritating me quite a LOT.

How so? I am just asking extremely interesting questions about video
technology.

Please, do yourself a favour: buy an Amazon book voucher and shut up.

I’ve tried painfully hard to answer my questions doing my own research
-- including reading information from books. I still haven’t found
answers to my questions. That is why I am turning to NGs for assistance.

AGGGHHHHH.... plonk

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xBACD7433
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[Brian Gregory [UK]]

"Green Xenon [Radium]" <glucegen1@excite.com> wrote in message
news:46f73fc6$0$32520$4c368faf@roadrunner.com...

On Sep 23, 3:02 pm, Brendan Gillatt
brendanREMOVET...@brendanREMOVETHISgillatt.co.uk> wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/4c903b0a453a39fa :

I’ve tried painfully hard to answer my questions doing my own research --
including reading information from books. I still haven’t found answers to
my questions. That is why I am turning to NGs for assistance.

Is Quadrature Frequency Modulation used? What for?

AFAIK, Quadrature Amplitude Modulation uses a combo of AM and
Phase-Shift-Keying.

So QFM would use a combination of FM and PSK. Would this decrease the
bandwidth required for broadcasting FM luminance video signals?

I did a Google Search for “Quadrature Frequency Modulation” on
http://www.google.com/search?hl=en&lr=&q=%22Quadrature+Frequency+Modulation+%22&btnG=Search

None of those pages made any sense to me.

I had a quick look at a few of them.

Some guy seems to be trying to patent something he calls Quadrature
Frequency Modulation. I see this as similar to the many perpetual motion
machines that get patented.

If it works at all I can't see it offering anything different from QPSK (aka
QAM4) in performance or bandwidth requirements.

--

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.

 

[Green Xenon [Radium]]

On Sep 24, 12:23 am, "Brian Gregory [UK]" <n...@bgdsv.co.uk> wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/e3f02036509d6ca6 :

" <gluceg...@excite.com> wrote in
messagenews:46f6f08e$0$16535$4c368faf@roadrunner.com...


So QFM would use a combination of FM and PSK.
Would this decrease the
bandwidth required for broadcasting
FM luminance video signals?

Think about it.
Obviously there is no way FM and PSK can
be going on at the same time in any
way that can convey separate information.

How about FM and FSK [Frequency-Shift-Keying]?

Would this work if FSK is used in place of PSK?

Worse still if you separately FM
modulate two signals that start in
quadrature with each other they won't
stay in quadrature.

Okay. Then what is the *practical* FM-equivalent of QAM?

 

[Green Xenon [Radium]]

On Sep 23, 2:36 pm, "Brian Gregory [UK]" <n...@bgdsv.co.uk> wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/6a386fec832f1ef5 :

" <gluceg...@excite.com> wrote in
messagenews:46f6d850$0$11068$4c368faf@roadrunner.com...


Hi:

One major reason the luminance signals of
television are broadcasted on an
AM-carrier instead of FM is
because FM requires large amounts of

bandwidth. Is there a way to use FM video
without hogging so much
bandwidth?

Quotes from

http://groups.google.com/group/sci.electronics.basics/msg/0c013cf5371da8dc?hl=en&

:

Multiple-level quadrature modulation,
"constellation modulation",
is most common for packing
lots of bits per Hz of bandwidth.
The more you pack,
the better the s/n ratio has to be.

http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation

http://en.wikipedia.org/wiki/Constellation_diagram

Does this mean that Quadrature Modulation
and Constellation Modulation
can -- at least in theory -- be applied
to FM video so that excessive
bandwidth is not needed? If so, then
what would be the minimum
radio-frequency required to transmit the video signal?

No.

These are like special modified forms of AM.

You can only use these to reduce
bandwidth of an FM signal in the same way
that you can use AM to reduce
the bandwidth of an FM signal.
It just won't
be FM any more.

Couldn’t the video signal first be converted to QAM, multiple-level
quadrature modulation, and/or constellation modulation and then
transmitted on a FM radio carrier?

AFAIK, the QAM/multiple-level-QM/ constellation-modulation version of
the video signal won’t require as much bandwidth as the original video
signal. The original video signal is first converted to bits and symbols
and then transmitted on an FM radio carrier. To make the best use of
bandwidth, limit the baud to only 1-symbol-per-second but pack as many
bits-per-symbol as feasible.

Quotes from http://en.wikipedia.org/wiki/Baud :

“Conveying more than one bit per symbol has advantages. It reduces the
time required to send a given quantity of data, and allows modern
modems, FDDI and 100/1000 Mbit/s Ethernet LANs, and others, to achieve
high data rates. An optimal symbol set design takes into account channel
bandwidth, desired information rate, noise characteristics of the
channel and the receiver, and receiver and decoder complexity. A typical
2400-bit/s modem transmits at 600 baud (600 symbol/s), where each
quadrature amplitude modulation symbol carries four bits of information.
1000 Mbit/s Ethernet LAN cables use many wire pairs and many bits per
symbol to encode their data payloads. 1000BASE-T uses four wire pairs
and two data bits per symbol to get a symbol rate of 125MBd.”

Quotes from
http://www.howstuffworks.com/framed.htm?parent=modem.htm&url=http://www.physics.udel.edu/wwwusers/watson/student_projects/scen167/thosguys/index.html
:

“So the technique is to try and "pack" as many bits as you can into 1 baud.”

So it’s always best to use the most amounts of bits-per-baud but no more
than 1 baud

bps = baud * number of bits per baud.

Remember, keep the baud no more than one-symbol-per-second but at the
same time, convey as many bits-per-symbol as mathematically and
physically possible.

Then, hopefully, it will be possible to transmit/receive video signals
on FM carriers with radio-frequencies below the medium-wave band --
without stealing bandwidth from existing stations using those
frequencies -- or frequencies near those stations.

http://en.wikipedia.org/wiki/Medium-wave

MW = from 530 kHz up to 1610 kHz

 

[Dave Platt]

In article <46f86fa7$0$9596$4c368faf@roadrunner.com>,
Green Xenon [Radium] <glucegen1@excite.com> wrote:

Then, hopefully, it will be possible to transmit/receive video signals
on FM carriers with radio-frequencies below the medium-wave band --
without stealing bandwidth from existing stations using those
frequencies -- or frequencies near those stations.

Hope all you want, guy.

Don't hold your breath while you're hoping for it, though.

To understand why, Google the "Shannon Limit".

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Brian Gregory [UK]]

"Green Xenon [Radium]" <glucegen1@excite.com> wrote in message
news:46f86fa7$0$9596$4c368faf@roadrunner.com...

Couldn’t the video signal first be converted to QAM, multiple-level
quadrature modulation, and/or constellation modulation and then
transmitted on a FM radio carrier?

AFAIK, the QAM/multiple-level-QM/ constellation-modulation version of the
video signal won’t require as much bandwidth as the original video signal.
The original video signal is first converted to bits and symbols and then
transmitted on an FM radio carrier. To make the best use of bandwidth,
limit the baud to only 1-symbol-per-second but pack as many
bits-per-symbol as feasible.

Why?????

Why make it use more bandwidth by introducing totally superfluous FM
modulation??

I'm beginning to think you are a troll.

--

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.

 

[Richard Crowley]

"Brian Gregory [UK]" wrote ...

Why make it use more bandwidth by introducing totally superfluous FM
modulation??

I'm beginning to think you are a troll.

Others have come to the same conclusion months ago.

 

[Sjouke Burry]

Brian Gregory [UK] wrote:

" <glucegen1@excite.com> wrote in message
news:46f86fa7$0$9596$4c368faf@roadrunner.com...
Couldn’t the video signal first be converted to QAM, multiple-level
quadrature modulation, and/or constellation modulation and then
transmitted on a FM radio carrier?

AFAIK, the QAM/multiple-level-QM/ constellation-modulation version of the
video signal won’t require as much bandwidth as the original video signal.
The original video signal is first converted to bits and symbols and then
transmitted on an FM radio carrier. To make the best use of bandwidth,
limit the baud to only 1-symbol-per-second but pack as many
bits-per-symbol as feasible.

Why?????

Why make it use more bandwidth by introducing totally superfluous FM
modulation??

I'm beginning to think you are a troll.

Stop wondering, he IS a troll, asking wrong,silly questions,

and crossposting all over the place, hoping to score from
people who think the questions are legit.

 

[Green Xenon [Radium]]

On Sep 25, 1:36 pm, "Brian Gregory [UK]" <n...@bgdsv.co.uk> wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/e85e65d92a479a00 :

" <gluceg...@excite.com> wrote in
messagenews:46f86fa7$0$9596$4c368faf@roadrunner.com...


Couldn’t the video signal first be
converted to QAM, multiple-level
quadrature modulation, and/or
constellation modulation and then
transmitted on a FM radio carrier?

AFAIK, the
QAM/multiple-level-QM/constellation-modulation
version of the
video signal won’t require as much
bandwidth as the original video signal.
The original video signal is first converted
to bits and symbols and then
transmitted on an FM radio carrier.
To make the best use of bandwidth,
limit the baud to only
1-symbol-per-second but pack as many
bits-per-symbol as feasible.

Why?????

Why make it use more bandwidth by
introducing totally superfluous FM
modulation??

I wish I could answer that question. It’s a matter of personal
preference. I’ve got this urge to get what I know I can’t have. FM video
is one of them. Hence, I want to do anything possible to transmit the
luminance component of video signals on FM without hogging excessive
bandwidth.

QAM/multiple-level-QM/constellation-modulation are examples of exotic
modulation techniques that allow you to transmit/receive the most amount
of information while using the least amount of bandwidth. To further
prevent excessive usage of bandwidth while maintaining signal
efficiency, the baud should be no more than 1-symbol-per-second while
the amounts of bits-per-symbol conveyed should be the most that is
physically and mathematically-possible.

Before being transmitted on the FM carrier, the luminance video signal
should be converted to QAM, multiple-level-QM, and/or
constellation-modulation. The
QAM/multiple-level-QM/constellation-modulation version of the video
signal won’t consume as much FM bandwidth as the original video signal.

If the original luma is transmitted on an FM carrier, the resulting
deviations in the frequency of the FM wave will be excessive. If the
QAM/multiple-level-QM/constellation-modulation equivalent of the luma is
transmitted, the resulting frequency-deviations will be significantly
smaller and hence use a lot less bandwidth.

I’ve got a neurological disorder which I would like to discuss briefly.
I am not trying to make excuses for any of my posts but I don’t want
readers to wrongly-assume that I troll/spam NGs just for attention. I am
really interested in the stuff I post about and wish that the readers
would not get upset at me.

I have a neurological disability called Asperger's Syndrome.

I would like to give you all some information about my disability. The
reason I am posting this message about Asperger's is to help avoid any
potential misunderstandings [though it's probably too late].

I have been diagnosed with Asperger's Syndrome (AS). AS is a
neurological condition that causes significant impairment in social
interactions. People with AS see the world differently and this can
often bring them in conflict with conventional ways of thinking. They
have difficulty in reading body language, and interpreting subtle cues.
In my situation, I have significant difficulty with natural
conversation, reading social cues, and maintaining eye contact. This can
lead to a great deal of misunderstanding about my intent or my behavior.
For example, I may not always know what to say in social situations, so
I may look away or may not say anything. I also may not always respond
quickly when asked direct questions, but if given time I am able express
my ideas.

On Usenet, the cyber-equivalent of my disability is probably noticed. I
do apologize profusely, for any inconvenience it causes.

Thank you very much in advance for your understanding, cooperation, and
assistance.


Regards,

Radium

 

[Dave Platt]

In article <46faa23a$0$7443$4c368faf@roadrunner.com>,
Green Xenon [Radium] <glucegen1@excite.com> wrote:

I wish I could answer that question. It’s a matter of personal
preference.

When your preferences are at odds with physical reality, guess which
wins?

QAM/multiple-level-QM/constellation-modulation are examples of exotic
modulation techniques that allow you to transmit/receive the most amount
of information while using the least amount of bandwidth. To further
prevent excessive usage of bandwidth while maintaining signal
efficiency, the baud should be no more than 1-symbol-per-second while
the amounts of bits-per-symbol conveyed should be the most that is
physically and mathematically-possible.

Mathematically, there's essentially no problem. All you need to do is
use a symbol representation which has enough discrete states to carry
the desired amount of information.

The problem here is "physically". Your proposal is very far out
beyond the point of physical realizability.

Video-grade luminance carries a lot of information. Just for grins,
let's say that it's the equivalent of a megabit per second - you can
get tolerable video at that bit rate using MPEG-2 or MPEG-4
compression of typical images. [An uncompressed/uncoded analog video
image requires a *lot* more bandwidth than this... maybe the
equivalent of 20-50 megabits per second?]

So, if you want only one symbol per second (one baud) to keep the
bandwidth down, you have to be able to transmit 1 megabit of
information in that one symbol. That requires that the symbol
representation include

1,000,000
2

different states. That is, the sender has to be able to choose from
among 2-to-the-millionth-power different voltages or RF levels (or QAM
or other constellation states), and the recipient needs to be able to
successfully distinguish between all of these states in order to
recover the megabit of information.

If you look at this in terms of the voltage being transmitted, it
means that the difference in voltage between any two adjacent states
must be large enough to be measured reliably. That would mean that
the _maximum_ voltage needs to be 2-to-the-millionth times higher.

If we want to ease the problem somewhat, we could use a QAM encoding,
with 2^1000 different amplitudes and 2^1000 different phases.

Even if you do that, the signal resolution you need is incredibly far
beyond what's physically possible. If you ran the entire system in a
bath of liquid helium (to keep the thermal noise level of all the
components down to a minimum), and you set the minimum voltage
difference between two states to something just barely above the
remaining thermal noise level ...

.... then the maximum voltage level produced by your transmitter will
still be billions of billions of billions of billions times (billions
*of* billions, not billions *and* billions) higher. It wouldn't just
burn out the transmitter... it would (if physically realizable) blow
everything in the solar system into incandescent plasma as soon as you
turned it on.

If the original luma is transmitted on an FM carrier, the resulting
deviations in the frequency of the FM wave will be excessive. If the
QAM/multiple-level-QM/constellation-modulation equivalent of the luma is
transmitted, the resulting frequency-deviations will be significantly
smaller and hence use a lot less bandwidth.

Don't bet on it. Remember that the abrupt transitions between QAM
states create a sudden discontinuity in the signal... which introduces
higher-frequency components or sidebands in your encoded luma signal.
These luma sidebands, once FM-modulated onto the carrier, will cause
RF sidebands out quite some distance. That's one of the gotchas of
FM... it creates sidebands which appear *further* away from the
carrier frequency than the maximum carrier deviation!

In short, there's no free lunch. For *any* given baseband signal
(straight, QAM-encoded, or whatever), an FM-modulated carrier will
*always* produce sidebands which go out as broadly as an AM carrier or
further, and will *never* take up less spectrum than an AM carrier
with the same baseband information.

In other words, no matter what coding tricks you can think up to try
to make FM video narrower than AM, you'll lose, because you can apply
the same coding tricks to the input of an AM modulator.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Green Xenon [Radium]]

On Sep 26, 2:03 pm, dpl...@radagast.org (Dave Platt) wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/a9872fef8b5bfab4 :

In article <46faa23a$0$7443$4c368...@roadrunner.com>,
Green Xenon [Radium] <gluceg...@excite.com> wrote:

QAM/multiple-level-QM/constellation-modulation are examples of exotic
modulation techniques that allow you to
transmit/receive the most amount
of information while using the least amount of bandwidth. To further
prevent excessive usage of bandwidth while maintaining signal
efficiency, the baud should be no more than 1-symbol-per-second while
the amounts of bits-per-symbol conveyed should be the most that is
physically and mathematically-possible.

Mathematically, there's essentially no problem. All you need to do is
use a symbol representation which has enough discrete states to carry
the desired amount of information.

The problem here is "physically". Your proposal is very far out
beyond the point of physical realizability.

Video-grade luminance carries a lot of information. Just for grins,
let's say that it's the equivalent of a megabit per second - you can
get tolerable video at that bit rate using MPEG-2 or MPEG-4
compression of typical images. [An uncompressed/uncoded analog video
image requires a *lot* more bandwidth than this... maybe the
equivalent of 20-50 megabits per second?]

So, if you want only one symbol per second (one baud) to keep the
bandwidth down, you have to be able to transmit 1 megabit of
information in that one symbol. That requires that the symbol
representation include

1,000,000
2

different states. That is, the sender has to be able to choose from
among 2-to-the-millionth-power different voltages or RF levels (or QAM
or other constellation states), and the recipient needs to be able to
successfully distinguish between all of these states in order to
recover the megabit of information.

If you look at this in terms of the voltage being transmitted, it
means that the difference in voltage between any two adjacent states
must be large enough to be measured reliably. That would mean that
the _maximum_ voltage needs to be 2-to-the-millionth times higher.

If we want to ease the problem somewhat, we could use a QAM encoding,
with 2^1000 different amplitudes and 2^1000 different phases.

Even if you do that, the signal resolution you need is incredibly far
beyond what's physically possible. If you ran the entire system in a
bath of liquid helium (to keep the thermal noise level of all the
components down to a minimum), and you set the minimum voltage
difference between two states to something just barely above the
remaining thermal noise level ...

... then the maximum voltage level produced by your transmitter will
still be billions of billions of billions of billions times (billions
*of* billions, not billions *and* billions) higher. It wouldn't just
burn out the transmitter... it would (if physically realizable) blow
everything in the solar system into incandescent plasma as soon as you
turned it on.

Can’t the maximum voltage be set to be low enough not to cause any
damage/injury to anyone/anything?

Also, couldn’t the temporal and spatial frequencies of the luminance
signal be downshifted prior to QM conversion so that not so many bits
are required?

It’s possible to downshift the frequencies of an audio signal without
low-pass-filtering or changing the speed at which it is played-back.
Couldn’t the equivalent be done with the temporal and spatial
frequencies of a luminance signal?

If the original luma is transmitted on an FM carrier, the resulting
deviations in the frequency of the FM wave will be excessive. If the
QAM/multiple-level-QM/constellation-modulation
equivalent of the luma is
transmitted, the resulting frequency-deviations will be significantly
smaller and hence use a lot less bandwidth.

Don't bet on it. Remember that the abrupt transitions between QAM
states create a sudden discontinuity in the signal... which introduces
higher-frequency components or sidebands in your encoded luma signal.
These luma sidebands, once FM-modulated onto the carrier, will cause
RF sidebands out quite some distance. That's one of the gotchas of
FM... it creates sidebands which appear *further* away from the
carrier frequency than the maximum carrier deviation!

In short, there's no free lunch. For *any* given baseband signal
(straight, QAM-encoded, or whatever), an FM-modulated carrier will
*always* produce sidebands which go out as broadly as an AM carrier or
further, and will *never* take up less spectrum than an AM carrier
with the same baseband information.

In other words, no matter what coding tricks you can think up to try
to make FM video narrower than AM, you'll lose, because you can apply
the same coding tricks to the input of an AM modulator.

Is there any thing that could be done to the QM signal so that the
resulting FM sidebands won’t be excessive?

In an FM carrier, the neutral frequency results when there is no
modulation signal. The FM carrier changes according to the modulator. If
the modulator voltage it positive, the FM carrier’s frequency increases.
When the modulator voltage becomes negative, the carrier’s frequency
decreases. On a graph of the modulator signal, the x-axis is where the
voltage is neutral. Above the x-axis, the voltage is positive. Below the
x-axis, the voltage is negative. The further from the x-axis the voltage
goes, the more broad the sidebands will be.

To prevent the sidebands from getting too broad, the QM signal needs to
have all to voltages shifted closer to the x-axis. This means the device
receiving the QM signals on the other end needs to be more sensitive to
differences in voltages.

Thus it would help if the physical voltage difference between what is
interpreted as 1 or 0 be much smaller. The smaller the change in
voltage, the less extreme the resulting FM sidebands.

 

[Dave Platt]

In article <46fc4458$0$16496$4c368faf@roadrunner.com>,
Green Xenon [Radium] <glucegen1@excite.com> wrote:

Can't the maximum voltage be set to be low enough not to cause any
damage/injury to anyone/anything?

Not if you want to actually be able to use the signal. That was my
point about "liquid helium". If you reduce the upper voltage enough
to be physically realizable, then the smallest voltage difference
you'd have to be able to distinguish is *far* less than the
inescapable amount of noise in the system, even at extremely cold
temperatures where thermal noise is minimized.

Also, couldn’t the temporal and spatial frequencies of the luminance
signal be downshifted prior to QM conversion so that not so many bits
are required?

Not enough to matter, by a factor of zillions to one.

It’s possible to downshift the frequencies of an audio signal without
low-pass-filtering or changing the speed at which it is played-back.
Couldn’t the equivalent be done with the temporal and spatial
frequencies of a luminance signal?

Once again, no, not enough to matter. If it was only a matter of 2:1
or 10:1, you might be able to do it. The one-baud scheme you propose
is off by a factor of 1,000,000,000,000,...,000 to 1 or so (*lots* of
zeros in there).

Go do as I said, and google "Shannon Limit". To sum it up: there's a
hard limit on the amount of information that you can send through a
communication channel which has (a) a finite bandwidth, and (2) a
finite signal-to-noise ratio.

Your goal of trying to pack video-grade information into small gaps in
the MW spectrum goes far beyond the Shannon limit.

Is there any thing that could be done to the QM signal so that the
resulting FM sidebands won’t be excessive?

In an FM carrier, the neutral frequency results when there is no
modulation signal. The FM carrier changes according to the modulator. If
the modulator voltage it positive, the FM carrier’s frequency increases.
When the modulator voltage becomes negative, the carrier’s frequency
decreases. On a graph of the modulator signal, the x-axis is where the
voltage is neutral. Above the x-axis, the voltage is positive. Below the
x-axis, the voltage is negative. The further from the x-axis the voltage
goes, the more broad the sidebands will be.

To prevent the sidebands from getting too broad, the QM signal needs to
have all to voltages shifted closer to the x-axis. This means the device
receiving the QM signals on the other end needs to be more sensitive to
differences in voltages.

Thus it would help if the physical voltage difference between what is
interpreted as 1 or 0 be much smaller. The smaller the change in
voltage, the less extreme the resulting FM sidebands.

Your understanding of FM modulation is incomplete, and it is leading
you astray. You're only looking at half of the picture. You need to
go back and hit the books again so that you understand the whole
situation.

Yes, it's true that the instantaneous carrier deviation depends only
on the amplitude of the modulation signal. However, that's only part
of the picture. Sidebands are created out *beyond* the maximum
carrier deviation frequency... and they are created at frequencies
which are at offset-multiples of the modulating frequency.

You *cannot* narrow an FM signal down to a width less than the
modulating frequency. If you want to carry (for example) an audio
signal with 20,000 Hz of audio bandwidth, then the modulated FM signal
will always have sidebands out as far as 20,000 Hz on either side of
the nominal carrier frequency. This is true NO MATTER HOW SMALL the
amplitude of the modulating signal, as long as there's any signal at
all.

If you FM-modulate a carrier with a very low-level 20 kHz tone, you
might be causing only 1 kHz of carrier deviation... but there will
still be sidebands 20 kHz above and below the nominal carrier
frequency. That may seem strange and counterintuitive, but it's how
the math works out, and how measurements confirm it works.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Dave Platt]

In article <46fc71d2$0$24285$4c368faf@roadrunner.com>,
Green Xenon [Radium] <glucegen1@excite.com> wrote:

Would 300:1 work?

Not for video, no.

The ULF is even lower-frequency than MW. If a baud of
20-symbols-per-second but 300 bits-per-symbol is used, can the luminance
signal have its temporal and spatial frequencies downshifted
sufficiently so that it can be on a ULF-frequency FM carrier? Will this
work even if the FM carrier’s center-frequency is 300 Hz?

No. No. And, no. You cannot possibly do this... for several reasons.

For one thing, trying to convey 300 bits of information per symbol is
still grossly optimistic. If you take a look at real-world modulation
systems (QAM64 and so forth) you'll find that they send much less
information per symbol... I don't have the best numbers available off
of the top of my head, but I'd be surprised if there's a system in
practical use which tries to send more than 16 bits per symbol. The
amount of noise on real-world communcation channels makes it
impractical-to-impossible to go much beyond that... and you are
proposing something *far* beyond that. Trust me - the laws of physics
in this universe won't permit you to do it.

For another thing, even if you *could* pack that much information into
a symbol, you'd still be capable of sending only 6000 bits per second.
That's far too little for anything resembling real video at real
resolutions... you couldn't even send one frame per second at that
rate.

For a third thing, the frequency content of a video luminance signal
starts just above DC, and goes up from there (to several MHz with
standard NTSC video). There really isn't any room for you to shift
the frequencies downwards by a useful amount... if you try, you end up
trying to shift real information down past DC. Either you lose it (if
you filter before shifting) or you *try* to shift it down past DC into
negative frequencies, and it aliases right back up into your passband
and distorts the rest of the signal.

To sum it up - what you're trying to do is fundamentally impossible.
It doesn't matter how you shift the luminance signal's frequencies
around. It doesn't matter how you modulate it. It doesn't matter
what tricks you play. You just don't have enough bandwidth available.
"You can't fool Mother Nature."

So there is no way to decrease how far the sidebands will go?

With FM? Nope, not in the way you're hoping. Modulate a carrier Fc
with a frequency Fm, and the first sidebands will be at Fc+Fm and
Fc-Fm, just as would be true with AM. That's the narrowest you can
get.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Richard Crowley]

"Dave Platt" wrote ...

No. No. And, no. You cannot possibly do this... for several reasons.

For one thing, trying to convey 300 bits of information per symbol is
still grossly optimistic. If you take a look at real-world modulation
systems (QAM64 and so forth) you'll find that they send much less
information per symbol... I don't have the best numbers available off
of the top of my head, but I'd be surprised if there's a system in
practical use which tries to send more than 16 bits per symbol. The
amount of noise on real-world communcation channels makes it
impractical-to-impossible to go much beyond that... and you are
proposing something *far* beyond that. Trust me - the laws of physics
in this universe won't permit you to do it.

Perhaps "Radium" should ask his questions over there in
that other universe where *his* laws of physics apply.

 

[Sjouke Burry]

Dave Platt wrote:

In article <46fc71d2$0$24285$4c368faf@roadrunner.com>,
Green Xenon [Radium] <glucegen1@excite.com> wrote:

Would 300:1 work?

Not for video, no.

The ULF is even lower-frequency than MW. If a baud of
20-symbols-per-second but 300 bits-per-symbol is used, can the luminance
signal have its temporal and spatial frequencies downshifted
sufficiently so that it can be on a ULF-frequency FM carrier? Will this
work even if the FM carrier’s center-frequency is 300 Hz?

No. No. And, no. You cannot possibly do this... for several reasons.

Yes he can.

As a known troll on many newsgroup he can do anything.
Eve hide under a bridge.

 

[Green Xenon [Radium]]

On Sep 29, 10:11 am, tonsofpcs <tonsof...@gmail.com> wrote
http://groups.google.com/group/uk.tech.digital-tv/msg/5d3083e46aff377a :

The only way I see of you getting something narrow in bandwidth to
transmit video luma would be to take it, and create a digital system
that has a very large number of discrete states, so large that the
lines between them seem to blur, and transmit it at a very high
frequency (or more, maybe even an ultra high frequency), with a large
number of bits per symbol (8 seems like a good number) but a very high
temporal resolution. You could even modulate a color subcarrier on
and add in chroma information on two axis, lets call them I and Q.
This will create a situation where the receiver will be receiving the
data with interference, but since you are only sending a small amount
of data at each temporal interval, any interference's effect within a
decent area will be negligible and the viewer's eye's will compensate.
On second thought, analog video is so much simpler (and exactly the
same, except it lacks discrete levels).

--
A confused Eric, wondering why you're trying to do this....

Well, my goal was to somehow receive QM video signal on a
frequency-modulated ULF [radio-frequency between 300 and 3,000 KHz]
carrier -- in which the QM uses only 1 baud but shoves as many
bits-per-symbol mathematically possible while setting the maximum
voltage of the discrete states low enough not to cause any harm to
anyone or anything [including the equipment itself] -- and with as many
discrete states [between the highest and lowest voltage] as
mathematically-possible. Unfortunately, reality does not want me doing
this and reality always has the last word as to what does and what
doesn’t occur.

Anyways, my next question. Is it possible to split the symbol of a 1
baud, 8-bit-per-symbol signal into 8 bits? I.e. in this case, a single
symbol would be split into 8 different parts each carrying one of the
bits. Is this possible? If so, would this be of any assistance to me?

 

[Richard Crowley]

"Green Xenon [Radium]" wrote ...

Anyways, my next question. Is it possible to split the symbol of a 1
baud, 8-bit-per-symbol signal into 8 bits? I.e. in this case, a single
symbol would be split into 8 different parts each carrying one of the
bits. Is this possible? If so, would this be of any assistance to me?

Sure it is possible. It won't be of any assistance to you (or to
anyone else since you can't put 8 pounds in a 1-pound sack.
Bandwidth is bandwidth, no matter how you slice it. Do you
really think that nobody has thought of various methods of
transmitting video over low-bandwidth paths? If so, you need
to study not only science and engineering but the HISTORY
of science and engineering.

 

[Green Xenon [Radium]]

On Sep 29, 5:20 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote in
http://groups.google.com/group/uk.tech.digital-tv/msg/88f1401cb2a43810 :

" wrote ...

Anyways, my next question. Is it possible to split the symbol of a 1
baud, 8-bit-per-symbol signal
into 8 bits? I.e. in this case, a single
symbol would be split into 8 different
parts each carrying one of the
bits. Is this possible? If so, would
this be of any assistance to me?

Sure it is possible. It won't be of any assistance to you (or to
anyone else since you can't put 8 pounds in a 1-pound sack.
Bandwidth is bandwidth, no matter how you slice it. Do you
really think that nobody has thought of various methods of
transmitting video over low-bandwidth paths? If so, you need
to study not only science and engineering but the HISTORY
of science and engineering.

There are 8-bits-per-symbol, only 1 baud. The symbol is split into 8
parts. Each part is 1-bit.

How is this “putting 8 pounds in a 1-pound sack?”

It’s more like “putting 1 pound in a 1-pound sack”

 

[Dave Platt]

In article <46fefb70$0$7493$4c368faf@roadrunner.com>,
Green Xenon [Radium] <glucegen1@excite.com> wrote:

Sure it is possible. It won't be of any assistance to you (or to
anyone else since you can't put 8 pounds in a 1-pound sack.
Bandwidth is bandwidth, no matter how you slice it. Do you
really think that nobody has thought of various methods of
transmitting video over low-bandwidth paths? If so, you need
to study not only science and engineering but the HISTORY
of science and engineering.

There are 8-bits-per-symbol, only 1 baud. The symbol is split into 8
parts. Each part is 1-bit.

How is this “putting 8 pounds in a 1-pound sack?”

It’s more like “putting 1 pound in a 1-pound sack”

You are using the word "split" without defining what you are meaning,
and I think you may be using the word "bit" in two different ways (as
in "a single binary digit's worth of information" and "a part")...
maybe I'm wrong about the latter.

Sure, you can carry 8 bits of information per symbol, at a rate of one
baud. That's an information rate of 8 bits per second, which isn't a
terribly useful amount of information.

What I *think* you are saying is something along the lines of

"If there's no way to carry N bits of information per symbol (where
N is a large number) at a rate of 1 symbol per second, in a
specified bandwidth, over a channel having a certain amount of
dynamic range / signal-to-noise ratio available, then I'd
like to somehow divide each symbol into eight sub-symbols which
each carry N/8 of the information, but which still make up only one
symbol per second. My hope is that these eight sub-symbols could
be easier to transmit, somehow, than a single symbol carrying N
bits, and that I could thus transmit them more easily but without
using any more bandwidth. Can I do that?"

If that's what you're asking, the answer is "no".

Once you hit the theoretical information limit of the communication
channel (which is set by the bandwidth you use and by the amount of
noise on the channel) you can't do any better than that. No matter
how you modulate (changing the baud rate, the amount of information
per symbol, etc.) you can't do better than this.

And, as we've been trying to make clear, your goal is quite far beyond
the theoretical limit. You just can't get there. You're trying to
put all of Lake Erie in a water-glass.

Let it go, Radium.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!