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I want to see SHF FM video signals.

R

Robert Peffers.

Jan 1, 1970
0
dxAce said:
You paranoid schizo's must always be aware.
Now what does that say about you who thinks you live in either a democracy
or a republic?

Do you think the innocent South American guy gunned down by several armed
London Police officers though he too was living in a democracy?
So too was the guy who called in at his, "Local", while carrying a table leg
he was going to repair and got shot without any chance to prove his
innocence.
Both the USA and the UK are now among the most repressed countries in the
entire World. Our leaders do just what they want with us and do so with
impunity.
Only mentally blind folk like you think you are still free and your
oppressors play upon your fear of whatever bogeyman they have conned you
into believing in.

Were YOU one of those who believed Iraq was behind the attack on the WTO?
Were YOU one of those conned into fear of Saddam's WMD that he did not have
Are you one of those who think the war on Islam is actually a war against
terrorists?

And you call me, "You paranoid schizo", while you are cowering in fear of a
terror attack.
--

Robert Peffers,
Kelty,
Fife,
Scotland, (UK).
 
I

Ian Jackson

Jan 1, 1970
0
Robert Peffers. said:
As far as I know there are two definitions of, "Republic",
1. A state where supreme power is held by the people, or their elected
representatives, or by an elected or nominated president.
2. Literally it means a society with equality between its members.
Does it 'literally' not mean a 'public thing', or 'a thing of the
people' (from your actual Latin 'res publicae')?

Ian.
--
 
A

Anim8rFSK

Jan 1, 1970
0
Robert Peffers. said:
Is there anything to prevent a republic also being democratic?
Yes

As far as I know there are two definitions of, "Republic",
1. A state where supreme power is held by the people, or their elected
representatives, or by an elected or nominated president.
2. Literally it means a society with equality between its members.

Neither of which is the definition of Republic.
While a democracy is -
1. (a), a system of government by the whole population, usu. through elected
representatives. (b), a state so governed. (c), any organization governed on
democratic principles.
2. an egalitarian and tolerant form of society.

Well, you got that wrong as well.
Can any USAsian really believe that they live in a Republic, (in the literal
sense of the word)?

Sure. We do.
Can any USAsian really believe that they live in a "Democracy", (in the
literal sense of the word)?

Yes. Many many many people incorrectly believe that. The press insists
on getting it wrong every day.
In effect both the USA and the UK are now, "Oligarchies"-

Except for the part where we're not.
Oligarchy,
1 government by a small group of people.
2 a state governed in this way.
3 the members of such a government.

Just consider how Bush and Blair took our two countries into wars that the
public, by the large, did not want and you will see that neither state is
either democratic nor republican.

Even if your statement were true, your conclusion still wouldn't be.
We elect these people as our servants to carry out our democratic wishes and
they then become the masters and we the servants. It is long past time for
the people of both democracies to reassert themselves and demand their
appointed servants remain their servants rather than their leaders and/or
masters.

Will I now have to beware of black 'copters at dawn?

I'm sure your level of dishonesty and delusion requires it.
 
A

Anim8rFSK

Jan 1, 1970
0
Robert Peffers. said:
Now what does that say about you who thinks you live in either a democracy
or a republic?

That we're smarter than you.
 
B

Bob Myers

Jan 1, 1970
0
Radium said:
Hi:

Video signals for NTSC, PAL, and SECAM television are transmitted on
AM carriers.

No, they're not. And there's no such thing as an "AM carrier"
or "FM carrier" to begin with. The carriers themselves are simply
signals at a given frequency. "AM" or "FM" refers to the modulation
IMPOSED on those carriers - in other words, how the information
to be carried is used to modify some aspect of the carrier signal.

In TV, most systems employ a version of AM to carry the luminance
(Y) signal; the color (chroma) information is carried via a somwhat
different version of AM, and the audio is most commonly FM.
The French SECAM system as originally implemented carried the
chroma information on TWO frequency-modulated subcarriers.
My question is, let's say I have a television set that is capable of
receiving and demodulating FM video carrier waves. What would I see on
the TV? I am aware that no company uses FM video. Would I see sawtooth-
like patterns on the screen due to frequency-modulated electric fields
present in the environment?

No.

I'd really like buy a TV with a FM-video receiver; I want to find out
what FM-video disturbances in the SHF [Super High Frequency ]
frequency-range look like. I am sick n' tired of AM video.

AM should be used for analog audio. FM should be used for digital
video.

Nonsense. The choices of AM and FM within the original analog
standard definitions were made for some very, very good reasons.
Digital television is a completely different beast, and is presently
broadcast using two very different modulation schemes - the
U.S. standard (ATSC) using 8-VSB, while the rest of the world
(mostly) will be using COFDM under the DVB-T standard.

Bob M.
 
R

Radium

Jan 1, 1970
0
Radium,

Some television is actually transmitted using FM modulation schemes, but not
for commercial broadcasting. Examples of FM TV are ham/amateur ATV/SSTV,
unlicensed 2.4 GHz surveillance links, and a number of point to point and
studio to transmitter systems. FM signaling provides benefits in noise
immunity and also permits better channel re-use, since it exploits one of
the best features of FM called "the FM capture effect", wherein nearly equal
strength signals which would otherwise interfere in AM systems will cause an
FM receiver to "capture" only the stronger signal and ignore the weaker,
even if differences of 1 dB of signal strength exists.

There is no specific answer to what you would see as far as video patterns,
and there is no reason whatsoever to expect to see sawtooth waveforms in
particular. The demodulated signal from FM will conform to the spectral
changes just as the demodulated signal from an AM detector would conform to
amplitude changes, and random noise would be considered "snow" in either
case. Unless a transmitted signal with a frequency ramp (sometimes called "a
chirp") is present, the video would have no sawtooth. A Doppler radar, for
example, could generate such a waveform, since some radars create chirped /
swept signals. The video scan rate(s) would additionally need to be in the
range of the chirp rate to create the appearance of a sawtooth.

FM disturbances in the SHF band are likely to be man-made and not
atmospheric, and thus only "viewable" if the "FM Video Receiver" you
envision had a demodulator / discriminator whose bandwidth was tailored to a
specific transmitted waveform, and even then only if sweep rates were
suitable. Absent a man-made transmitter, the SHF environment is mostly
thermal noise (both circuit and atmospheric) and only a radio telescope or
other enormous aperture / antenna will see beyond the atmosphere.

The choice of using AM versus FM is really way more complicated than "AM for
audio" or "FM for digital video". When designing communication systems of
any type, the engineer is faced with balancing many issues, and the channel,
media, noise environment, interference sources, power budget, multipath,
complexity, and cost are only a few of the considerations involved. A highly
reliable cable modem to transmit fast digital content may indeed by phase
modulated with an amplitude trellis; a secure and interference resistant
link may use spread-spectrum frequency hopping AM for digital signaling; and
FM winds up being used heavily in many voice communication systems mostly
because the capture effect reduces co-channel interference.

The closest I can suggest to what you might enjoy exploring would be a
satellite dish and receiver designed for L band which will see and decode
some broadcasting which is unprotected / unencrypted. It gets you into the
range of SHF, has true TV signaling for public viewing, and is a hobbyist
activity with others involved.

Smarty, big thanks for your detailed response. One big advantage [that
I could imagine] to using FM -- instead of AM -- to carry the
luminance (Y) signal, is that you can run on your treadmill without
seeing those lines on the screen mask your favorite shows. The
magnetic signals generated by the electronics in the treadmill causes
blinding interference on AM video. FM video is be immune to such
disruptions.
 
R

Radium

Jan 1, 1970
0
No, they're not. And there's no such thing as an "AM carrier"
or "FM carrier" to begin with. The carriers themselves are simply
signals at a given frequency. "AM" or "FM" refers to the modulation
IMPOSED on those carriers - in other words, how the information
to be carried is used to modify some aspect of the carrier signal.

Okay. Thanks for clearing this up.
In TV, most systems employ a version of AM to carry the luminance
(Y) signal; the color (chroma) information is carried via a somwhat
different version of AM, and the audio is most commonly FM.
The French SECAM system as originally implemented carried the
chroma information on TWO frequency-modulated subcarriers.

Why not carry the luminance-signal on FM and the audio-signal on AM?
I'd really like buy a TV with a FM-video receiver; I want to find out
what FM-video disturbances in the SHF [Super High Frequency ]
frequency-range look like. I am sick n' tired of AM video.
AM should be used for analog audio. FM should be used for digital
video.
Nonsense. The choices of AM and FM within the original analog
standard definitions were made for some very, very good reasons.
Digital television is a completely different beast, and is presently
broadcast using two very different modulation schemes - the
U.S. standard (ATSC) using 8-VSB, while the rest of the world
(mostly) will be using COFDM under the DVB-T standard.

Couldn't FSK [the digital equivalent of FM] be used for luminance [Y]
signal of the digital video?
 
B

Brenda Ann

Jan 1, 1970
0
Radium said:
Why not carry the luminance-signal on FM and the audio-signal on AM?

The reasons (primarily) behind using the AM visual and FM aural signals for
television are:

Visual: Bandwidth. Visual uses what is called 'vestigial sideband'. This
means that basically only one sideband carries the modulation, with only a
vestige of the other sideband remaining, thereby reducing the bandwidth
needed for the visual signal by a significant factor. If FM were used, the
entire symmetrical waveform would have to be used, and would use a lot more
bandwidth. (Analog satellite television does/did use FM modulation, on the
order of 36 MHz IIRC, but bandwidth in the GHz ranges isn't at as much of a
premium as on relatively crowded VHF and UHF frequencies

Aural: Coverage. The aural signal (which is sent separately from the visual)
is only about 10% of the power of the visual signal.
 
R

Robert Peffers.

Jan 1, 1970
0
Ian Jackson said:
Does it 'literally' not mean a 'public thing', or 'a thing of the people'
(from your actual Latin 'res publicae')?

Ian.
republic / n.
1 a state in which supreme power is held by the people or their elected
representatives or by an elected or nominated president, not by a monarch
etc.
2 a society with equality between its members (the literary republic).
[French république from Latin respublica, from res 'concern' + publicus
public]

A, "Cut & Paste", from Concise Oxford Dictionary.
--

Robert Peffers,
Kelty,
Fife,
Scotland, (UK).
 
B

Bob Myers

Jan 1, 1970
0
Radium said:
Smarty, big thanks for your detailed response. One big advantage [that
I could imagine] to using FM -- instead of AM -- to carry the
luminance (Y) signal, is that you can run on your treadmill without
seeing those lines on the screen mask your favorite shows. The
magnetic signals generated by the electronics in the treadmill causes
blinding interference on AM video. FM video is be immune to such
disruptions.

Unless your treadmill is doing something very unusual, the interference
you are seeing is unlikely to be coming in via the RF "front end" of
the TV (where the video demodulation is taking place), and so switching
to FM from AM wouldn't help. (It's more than likely either magnetic
interference upsetting the deflection fields - assuming a CRT-type TV
- or the effects of noise coming in on the AC wiring.)

FM for standard "analog" TV is virtually impossible due to the bandwidth
requirements of typical FM itself. In the case of "digital" TV - well,
for the moment, let's just say that the modulation system used is
considerably different than anything we're talking about here, and
leave it at that, OK?

Bob M.
 
R

Robert Peffers.

Jan 1, 1970
0
Anim8rFSK said:
Neither of which is the definition of Republic.

Well, you got that wrong as well.

Sure. We do.

Yes. Many many many people incorrectly believe that. The press insists
on getting it wrong every day.

Except for the part where we're not.

Even if your statement were true, your conclusion still wouldn't be.

I'm sure your level of dishonesty and delusion requires it.

I'm so pleased to meet someone who considers themselves a much better
authority on the English language than the Oxford Dictionary.
Keep up the good work.

Perhaps you could also define for us the meaning of, "Extraordinary
Rendition", "Illegal Combatant", and, "Insurgent"?
--

Robert Peffers,
Kelty,
Fife,
Scotland, (UK).
 
B

Bob Myers

Jan 1, 1970
0
Why not carry the luminance-signal on FM and the audio-signal on AM?

See the previous post; it's basically a matter of the enormous bandwidth
requirements of FM (note that the standard "deviation" in FM *audio*
broadcast - a measure of how "wide" the overall signal will be - is +/-
75 kHz from the nominal carrier frequency, for a 15 kHz audio bandwidth.
The relationship between the transmitted signal bandwidth and the original
signal bandwidth in FM is not a simple one, but let's just leave it at the
point of noting that video signals are bandwidth hogs, and TV doesn't
even use regular-old-AM as a result of that. (The luminance signal is
actually sent via "vestigal sideband AM," one step removed from full
suppressed-carrier SSB.)

The audio is FM both to avoid the problems of interference bothering the
sound (just as in FM radio), AND to minimize the effects of the
video portions of the signal possibly interfering with the audio. A TV
channel, though, has relatively lots of room for audio.
Nonsense. The choices of AM and FM within the original analog
standard definitions were made for some very, very good reasons.
Digital television is a completely different beast, and is presently
broadcast using two very different modulation schemes - the
U.S. standard (ATSC) using 8-VSB, while the rest of the world
(mostly) will be using COFDM under the DVB-T standard.

Couldn't FSK [the digital equivalent of FM] be used for luminance [Y]
signal of the digital video?

FSK isn't exactly "the digital equivalent of FM" in the first place, and
the short form answer is no. Digital video is carried in a completely
difference manner, and there isn't exactly a readily-separable
luminance "signal" as such in the transmitted signal, at least not as
something you could identify on a scope as in analog TV - it's all just
bits, and it's all packetized.

Bob M.
 
R

Robert Peffers.

Jan 1, 1970
0
Rich Grise said:
None of this crap belongs in sci.electronics.basics. snip
..
I'm sure your post should not be top posted either nor cross-poster to,
"sci.electronics.basics,rec.video.desktop,rec.radio.shortwave,uk.radio.amateur,rec.arts.tv",
where you posted it too. Ever heard the expression, "Let he who is without
sin cast the first stone"?
--

Robert Peffers,
Kelty,
Fife,
Scotland, (UK).
 
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