Visual "clipping"?
Radium
Clipping in an audio signal results when an audio device receives a
signal that is too loud. The audio signal distorts into square-waves
because the "tops" of the signal are flattened. The device cannot
handle power levels over a certain level. When this level is exceeded,
clipping occurs. Clipping is usually harsher in digital devices than
in analog devices. Analog clipping tends to be fuzzy and soft compared
to digital clipping.
What is the visual-equivalent of "clipping"? Is there a difference
between analog and digital in terms of visual-clipping? If so, what is
the difference?
Auditory-clipping can damage speakers. Can visual-"clipping" damage
monitors?
Thanks,
Radium
isw
Radium <gluc...@gmail.com> wrote:
> Hi:
>
> Clipping in an audio signal results when an audio device receives a
> signal that is too loud. The audio signal distorts into square-waves
> because the "tops" of the signal are flattened. The device cannot
> handle power levels over a certain level. When this level is exceeded,
> clipping occurs. Clipping is usually harsher in digital devices than
> in analog devices. Analog clipping tends to be fuzzy and soft compared
> to digital clipping.
>
> What is the visual-equivalent of "clipping"? Is there a difference
> between analog and digital in terms of visual-clipping? If so, what is
> the difference?
Clipping causes whites lose all texture -- very similar to overexposed
film.
> Auditory-clipping can damage speakers. Can visual-"clipping" damage
> monitors?
No. Prolonged blacks can damage television transmitters, however (video
is inverted for transmission, so black requires full power from the
transmitter).
Isaac
Radium
> In article <1188874984.222039.197...@y42g2000hsy.googlegroups.com>,
> Radium <gluceg...@gmail.com> wrote:
> > Hi:
> > Clipping in an audio signal results when an audio device receives a
> > signal that is too loud. The audio signal distorts into square-waves
> > because the "tops" of the signal are flattened. The device cannot
> > handle power levels over a certain level. When this level is exceeded,
> > clipping occurs. Clipping is usually harsher in digital devices than
> > in analog devices. Analog clipping tends to be fuzzy and soft compared
> > to digital clipping.
> > What is the visual-equivalent of "clipping"? Is there a difference
> > between analog and digital in terms of visual-clipping? If so, what is
> > the difference?
> Clipping causes whites lose all texture -- very similar to overexposed
> film.
What does this look like on a screen?
> > Auditory-clipping can damage speakers. Can visual-"clipping" damage
> > monitors?
> No. Prolonged blacks can damage television transmitters, however (video
> is inverted for transmission, so black requires full power from the
> transmitter).
Prolonged black can damage a monitor/screen? That's weird. White is
analogous to the loudest sound a loudspeaker can playback. Black is
analogous to a loudspeaker not being feed any signal.
When the power-supply of the monitor/screen is turned off, the monitor/
screen is black because it not receiving any voltage.
I would think that extremely-bright white would damage the screen
because the brightest white results from the highest voltage applied
to the Reds, Greens, and Blues [equal intensities of R, G, & B -- if
combined -- appear white to our eyes when emitted by an electronic
monitor] in a particular area of the monitor/screen. If the voltage
exceeds this for prolonged periods of time, that region of the screen
will burn out, much like forcing an extremely-high voltage audio
signal into a speaker will cause the speaker to short-circuit and the
diaphragm to pop and/or melt. Many instructions manual for speakers
give direction not to reach or go above the clipping point and
clipping damages the speakers. Wouldn't something similar happen to a
monitor/screen [whether it's a CRT, plasma, or LCD] if it was forced
to display light-intensities beyond its limits?
Richard Crowley
> Radium wrote:
>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>> monitors?
>
> No. Prolonged blacks can damage television transmitters, however (video
> is inverted for transmission, so black requires full power from the
> transmitter).
Prolonged bright areas (whether clipped or not) will damage CRT
monitors. I have two on the bench right now to have their CRTs
replaced because the image is burned-in. They came from a
security/survelience application and you can somewhat see the
hallway and the doors they were monitoring.
Matt Ion
> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
>
>> In article <1188874984.222039.197...@y42g2000hsy.googlegroups.com>,
>
>> Radium <gluceg...@gmail.com> wrote:
>
>>> Hi:
>
>>> Clipping in an audio signal results when an audio device receives a
>>> signal that is too loud. The audio signal distorts into square-waves
>>> because the "tops" of the signal are flattened. The device cannot
>>> handle power levels over a certain level. When this level is exceeded,
>>> clipping occurs. Clipping is usually harsher in digital devices than
>>> in analog devices. Analog clipping tends to be fuzzy and soft compared
>>> to digital clipping.
>
>>> What is the visual-equivalent of "clipping"? Is there a difference
>>> between analog and digital in terms of visual-clipping? If so, what is
>>> the difference?
>
>> Clipping causes whites lose all texture -- very similar to overexposed
>> film.
>
> What does this look like on a screen?
An area of just plain white.
>>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>>> monitors?
>
>> No. Prolonged blacks can damage television transmitters, however (video
>> is inverted for transmission, so black requires full power from the
>> transmitter).
>
> Prolonged black can damage a monitor/screen? That's weird.
TRANSMITTERS. HE SAID TRANSMITTERS.
> White is
> analogous to the loudest sound a loudspeaker can playback. Black is
> analogous to a loudspeaker not being feed any signal.
NOT ON A TRANSMITTER. Yeesh. Did you actually read that paragraph AT
ALL???
Matt Ion
ANY static image for a prolonged time will cause burn-in on a CRT or
plasma display. The brighter it is, the less time it takes, but it
doesn't have to be pure white for burn to occur. Simply displaying 100%
white won't cause instant death of a monitor, however, the way a clipped
signal can damage a speaker.
Radium
> Prolonged bright areas (whether clipped or not) will damage CRT
> monitors.
Can damage occur to a CRT/Plasma/LCD monitor from an area that is
extremely-bright for an extremely short time? Let's say one attempts
to force 2400 lumens of light-intensity out of an area of the monitor
for around 5 seconds. What damage would affect that region of the
screen?
Warning! Crazy scenarios are presented below. None-the-less I still
find them interesting:
Try to force 100,000,000 lumens out of a square-shaped, pinky-finger-
sized area of an LCD monitor. Now what would happen? Would the organic
material present in that area catch fire?
For an acoustic-analogy, let's say one tries to force a 400,000 Hz,
144 dB sine-wave tone out of a Bose loudspeaker. The result: a very
expensive fire. The plastics/paper in the speaker would likely ignite.
Matt Ion
> On Sep 3, 9:25 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote:
>
>> Prolonged bright areas (whether clipped or not) will damage CRT
>> monitors.
>
> Can damage occur to a CRT/Plasma/LCD monitor from an area that is
> extremely-bright for an extremely short time? Let's say one attempts
> to force 2400 lumens of light-intensity out of an area of the monitor
> for around 5 seconds. What damage would affect that region of the
> screen?
Ummm, probably none, as the output would be limited by the drive systems
of the display. The only thing you could "force" into it would be a
high-voltage video signal, which would fry the input circuitry, but
probably not a lot else.
To extend the analogy to audio, your speaker would have its own built-in
amp with limited output power; you can't "force" it to output more power
into the speaker.
> Warning! Crazy scenarios are presented below. None-the-less I still
> find them interesting:
>
> Try to force 100,000,000 lumens out of a square-shaped, pinky-finger-
> sized area of an LCD monitor. Now what would happen? Would the organic
> material present in that area catch fire?
And how exactly would one do that, since LCDs don't actually produce
light on their own?
Ron N.
> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
> > > What is the visual-equivalent of "clipping"? Is there a difference
> > > between analog and digital in terms of visual-clipping? If so, what is
> > > the difference?
> > Clipping causes whites lose all texture -- very similar to overexposed
> > film.
>
> What does this look like on a screen?
If you can find an old analog TV or monitor, just turn up the contrast
control way too high. All the greys darker than a certain level
become black, all the greys lighter than a certain level become
white. Information is lost.
Martin Heffels
>NOT ON A TRANSMITTER. Yeesh. Did you actually read that paragraph AT
>ALL???
Usually he only reads half. Get used to the phenomenon "Radium".
-m-
--
Official website "Jonah's Quid" http://www.jonahsquids.co.uk
Martin Heffels
>Clipping causes whites lose all texture -- very similar to overexposed
>film.
White clipping makes you loose the texture, and some other interesting
things occur, like the clipped area turning yellowish (solarization).
But it's not only white which can clip, with colour-correction you can
easily clip one of the three colour-channels. And of course you can clip
black as well, loosing shadow detail.
>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>> monitors?
>
>No. Prolonged blacks can damage television transmitters, however (video
>is inverted for transmission, so black requires full power from the
>transmitter).
I would say the transmitters would be resistant to that. Most run below
their designed maximum power anyway.
cheers
-martin-
isw
Radium <gluc...@gmail.com> wrote:
> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
>
> > In article <1188874984.222039.197...@y42g2000hsy.googlegroups.com>,
>
> > Radium <gluceg...@gmail.com> wrote:
>
> > > Hi:
>
> > > Clipping in an audio signal results when an audio device receives a
> > > signal that is too loud. The audio signal distorts into square-waves
> > > because the "tops" of the signal are flattened. The device cannot
> > > handle power levels over a certain level. When this level is exceeded,
> > > clipping occurs. Clipping is usually harsher in digital devices than
> > > in analog devices. Analog clipping tends to be fuzzy and soft compared
> > > to digital clipping.
>
> > > What is the visual-equivalent of "clipping"? Is there a difference
> > > between analog and digital in terms of visual-clipping? If so, what is
> > > the difference?
>
> > Clipping causes whites lose all texture -- very similar to overexposed
> > film.
>
> What does this look like on a screen?
Just as I said: white areas with no texture.
> > > Auditory-clipping can damage speakers. Can visual-"clipping" damage
> > > monitors?
>
> > No. Prolonged blacks can damage television transmitters, however (video
> > is inverted for transmission, so black requires full power from the
> > transmitter).
>
> Prolonged black can damage a monitor/screen? That's weird. White is
> analogous to the loudest sound a loudspeaker can playback. Black is
> analogous to a loudspeaker not being feed any signal.
I did not say "monitor"; I said "transmitter". There *is* a difference.
> When the power-supply of the monitor/screen is turned off, the monitor/
> screen is black because it not receiving any voltage.
It's not voltage; it's current, that determines brightness during the
normal operation of a monitor.
> I would think that extremely-bright white would damage the screen
> because the brightest white results from the highest voltage applied
> to the Reds, Greens, and Blues [equal intensities of R, G, & B -- if
> combined -- appear white to our eyes when emitted by an electronic
> monitor] in a particular area of the monitor/screen.
Actually it's not voltage; it's current.
And it takes a long time for overdriving to cause damage to an ordinary
monitor.
> Wouldn't something similar happen to a
> monitor/screen [whether it's a CRT, plasma, or LCD] if it was forced
> to display light-intensities beyond its limits?
CRT's possibly, over a long period of time. LCDs, never. The LCD part is
just a bunch of "valves"; the light source is usually a fluorescent lamp
of some sort. No possibility of "burning anything out".
I have been involved with very special CRT-based imaging devices where
an uncontrolled momentary pulse would destroy the phosphor -- and in
fact, *drill a pit in the glass of the faceplate*. But that is unlikely
to ever happen to a CRT used as a video monitor.
Isaac
Paul Mitchum
[..]
> What is the visual-equivalent of "clipping"?
Blowouts.
> Is there a difference between analog and digital in terms of
> visual-clipping?
Yup.
> If so, what is the difference?
Google is your friend.
--
http://www.xoverboard.com/cartoons/2007/070416_argument.html
Matt Ion
Guess it's more of a THEORETICAL damage :)
I think the point is, the way they work, it's POSSIBLE, if unlikely.
Martin Heffels
>I think the point is, the way they work, it's POSSIBLE, if unlikely.
Yes of course :-) They would switch off with all the protections in place.
But it must have happened at one stage, otherwise it wouldn't be known.
-m-
glen herrmannsfeldt
(snip)
> What is the visual-equivalent of "clipping"? Is there a difference
> between analog and digital in terms of visual-clipping? If so, what is
> the difference?
Clipping results from the saturation of the system, analog or digital.
That should be true for audio or video.
> Auditory-clipping can damage speakers. Can visual-"clipping" damage
> monitors?
In general, audio clipping does not damage speakers. The usual
case that causes damage is the combination of a few things:
Using multiple drivers to cover a large frequency range, with
a crossover network to divide up the signal.
Musical audio has much more power at lower frequencies than higher
frequencies, so speakers are designed appropriately.
Clipping generates a lot of power at the higher harmonics of the
input frequencies that goes to drivers not designed for
those power levels.
In most video systems this combination doesn't exist. It might
in future video reproduction systems, though.
-- glen
Battleax
think far beyond it's capacity
ASAAR
>> Try to force 100,000,000 lumens out of a square-shaped, pinky-finger-
>> sized area of an LCD monitor. Now what would happen? Would the organic
>> material present in that area catch fire?
>
> And how exactly would one do that, since LCDs don't actually produce
> light on their own?
You and I couldn't, but an engineer/technician working for a
company such as GE, Westinghouse, Philips or Osram might go mad and
try something like that. If we suffered that same fate we might try
applying 240V A.C. to a 2.6v PR2 bulb to see "what would happen". :)
Don Stauffer in Minnesota
Yes, there IS a difference between analog and digital processing. The
analog effect depends on the stability of the analog signal
processing. This effect would appear on the horizontal trace of a TV
signal (part of the video path on today's TVs are still analog, even
with a "digital tuner". It can cause a ringing after the saturation,
and "artifacts" beyond the clipped area.
If certain types of processing are used, especially sharpening, in
digital signal processing, such artifacts can also end up surrounding
(in both directions) a clipped area.
Don Bowey
1188878846....@d55g2000hsg.googlegroups.com, "Radium"
<gluc...@gmail.com> wrote:
> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
>
snip
>
>> No. Prolonged blacks can damage television transmitters, however (video
>> is inverted for transmission, so black requires full power from the
>> transmitter).
>
> Prolonged black can damage a monitor/screen? That's weird. White is
> analogous to the loudest sound a loudspeaker can playback. Black is
> analogous to a loudspeaker not being feed any signal.
snip
More Trolling.
Exactly where did he say prolonged black can damage a monitor/screen
Michael A. Terrell
No, only the sync tips are at 100%.
--
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
Michael A. Terrell
Never worked at a TV transmitter site, have you? If they are
operating under the specified power, they are in violation of their
license, and no one is stupid enough to overbuy on the transmitter
requirements. The sync tips are at 100% power, and varies between full
white or black as required. Neither will damage the transmitter if left
continuously. In the early days of TV it was very common to fade to
black before and after a commercial, because everything was done by
hand. The black allowed switching sources without displaying any
glitches cause by the relay operated video switchers of the day. AFRTS
was still using relay type video switching in at least one TV station in
1974.
Martin Heffels
<mike.t...@earthlink.net> wrote:
> Never worked at a TV transmitter site, have you? If they are
>operating under the specified power, they are in violation of their
>license, and no one is stupid enough to overbuy on the transmitter
>requirements.
Help me here..... Since when would this be a violation? A
transmitter-license usually states the _maximum_ amount of power, so what
is different here? Stories are plenty of radio and television-stations
cutting down their power for power-saving reasons (money, money, money).
Michael A. Terrell
>
> On Tue, 04 Sep 2007 12:23:52 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
>
> > Never worked at a TV transmitter site, have you? If they are
> >operating under the specified power, they are in violation of their
> >license, and no one is stupid enough to overbuy on the transmitter
> >requirements.
>
> Help me here..... Since when would this be a violation? A
> transmitter-license usually states the _maximum_ amount of power, so what
> is different here? Stories are plenty of radio and television-stations
> cutting down their power for power-saving reasons (money, money, money).
In the US a station has to notify the FCC if they are not operating
at the power they are licensed for. It has to be logged on a set
schedule and kept in the station's permanent files for the FCC field
inspectors. If a station is operating below the level they are licensed
for, they are not serving the area they agreed to provide service to.
VERY few stations were ever allowed to differ from their rated power.
The only two I ever saw were on military bases where the transmitter
power was listed, with "Or as deemed necessary". These were in remote
locations and major repairs were consider as 'Depot Level' repairs.
Reduced or increased power was allowed, to stay on the air, but none of
these were high power stations. The license was deemed a 'Courtesy
License' by the FCC, which meant that they had little authority over a
military transmitter, but the 'Courtesy License' was granted to make
sure the frequency coordinators didn't assign a civilian station an
allocation that would interfere.
If your power level is too high, you can cause problems for other
stations, and if it's too low, your advertisers will demand refunds.
I was a broadcast engineer at one military and two civilian TV
stations over a 17 year period. I lost count of the AM radio stations I
did work for, or located parts and equipment to keep on the air.
Gene E. Bloch
However, the original remark was not about the *licensed* power, it was
about the *rated* power. I.e., the electrical or electronic limits, not
the legal limits.
--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")
Richard Crowley
> However, the original remark was not about the *licensed* power, it was
> about the *rated* power. I.e., the electrical or electronic limits, not
> the legal limits.
But as Mr. Terrell also observed, profit-making businesses don't
commonly waste money buying an over-powered transmitter.
They are frightfully expensive in any case.
Allen
a TV transmitter?
Allen
Michael A. Terrell
Are you kidding? The radium troll barely has enough neurons to pound
out his drivel.
Michael A. Terrell
Its obvious that you've never built a TV station from the ground up.
Even a spare 10% transmitter power capacity could cost a couple hundred
thousand dollars in capital assets. and its unlikely the governing
agency will allow you to use equipment capable of excess power, any more
than you can build whatever tower height you want. It costs millions of
dollars to build a full power commercial TV station.
Gene E. Bloch
Do you *really* think I've never built a TV station form the ground up?
Really?
Well, you're correct. It doesn't keep from speculating, however.
For example, it *might* be true that it's a good idea to spend extra
money to put in safety factors (although, to be fair, I *do* run my
100W lightbulbs at 100W). It could be cheaper in the long run than
fixing the reasult of not doing so.
The above has certinaly been true in civil construction for millennia.
Tim Wescott
on them?
Not.
Any system has to be designed with some sort of limits in mind. If the
broadcasters want to make decisions about how much of a screen can be
black and for how long, it's their decision to make.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Jerry Avins
> Richard Crowley wrote:
>> "isw" wrote ...
>>> Radium wrote:
>>>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>>>> monitors?
>>> No. Prolonged blacks can damage television transmitters, however (video
>>> is inverted for transmission, so black requires full power from the
>>> transmitter).
>>
>> replaced because the image is burned-in. They came from a
>> security/survelience application and you can somewhat see the
>> hallway and the doors they were monitoring.
>
> ANY static image for a prolonged time will cause burn-in on a CRT or
> plasma display. The brighter it is, the less time it takes, but it
> doesn't have to be pure white for burn to occur. Simply displaying 100%
> white won't cause instant death of a monitor, however, the way a clipped
> signal can damage a speaker.
Speaker damage occurs when the *speaker* clips. It's a result of the
voice coil hammering against the stops. Woofers and midranges are
protected from the high frequencies that clipping in the amplifier
generates by their crossover networks. If a tweeter isn't underrared as
tweeters often are, they won't be damaged by the acceleration forces.
When an amplifier clips, there's no longer feedback to lower its output
impedance, and the high output impedance also protects the speaker from
amplifier overload.
There are few speakers that can withstand the full output of a 500 W
amplifier even when the amplifier doesn't clip. Speaker ratings apply to
short bursts of power, not continuous abuse. A 10%-efficient speaker
driven at 500 watts is having 450 W of heat pumped into it. A two-slice
toaster runs about 800 W. How long before the voice coil smokes?
Transmitter and amplifier tubes have two ratings: CCS and ICAS*. There
is significant difference. Speakers are rated what I call MDFR**. What
will the salespeople tell you, that the rating is bogus or that clipping
burned it out?
Jerry
________________________________________
* "Continuous commercial service" and "intermittent commercial and
amateur service".
** "Market-driven fictitious rating"
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Richard Owlett
>[snip]
>
> Never worked at a TV transmitter site, have you? If they are
> operating under the specified power, they are in violation of their
*WHAT?*
Please quote a specific regulation that _prohibits_ operating at *LESS*
than authorized power. My commercial license (2nd class phone) may have
expired 40 years ago, but I never heard of such. We even had a backup
1Kw transmitter for when our 50Kw transmitter went down. There were
occasions (ice storms) when we switched to backup BEFORE primary went
down as it was more tolerant of bad SWR. [now this was an FM rather than
TV but don not see difference for this case]
Michael A. Terrell
>
> > On 9/04/2007, Michael A. Terrell posted this:
> >
> > Even a spare 10% transmitter power capacity could cost a couple hundred
> > thousand dollars in capital assets. and its unlikely the governing
> > agency will allow you to use equipment capable of excess power, any more
> > than you can build whatever tower height you want. It costs millions of
> > dollars to build a full power commercial TV station.
>
>
> Really?
>
> Well, you're correct.
I HAVE built a complete TV station, starting with an empty building
and no tower.
> It doesn't keep from speculating, however.
Speculate all you want, and let everyone see that you have absolutely
no grasp of the subject.
> For example, it *might* be true that it's a good idea to spend extra
> money to put in safety factors (although, to be fair, I *do* run my
> 100W lightbulbs at 100W). It could be cheaper in the long run than
> fixing the reasult of not doing so.
Do you know that a TV station's EIRP is transmitter power output,
multiplied by antenna gain?
> The above has certinaly been true in civil construction for millennia.
The only 'Civil' Engineering of a TV station is the buildings, and
the towers. The rest is Electronics, which is a different discipline,
with different rules.
Michael A. Terrell
That is an emergency situation, not normal operation. If any single
emergency lasted more than three days, the FCC required notification. If
a station is 'dark' more than a set number of days because of equipment
failure, they can lose their operating license, and have to fight anyone
else who wants that frequency allocation when they reapply for a
operating license. They may also be required to repalce any oldder, adn
all defective equipment that was grandfathered under the old operating
license.
All the FCC requlations are part of Title 47 CFR, so help yourself at
the link below. There are months of reading involvled to wade through
all of it.
http://www.gpoaccess.gov/cfr/index.html
Jerry Avins
At least at one time, a station's backup transmitter could have lower
power than it's main, and anything went if it was the only way to put a
station on the air at all. Nobody liked it, but it was considered better
than dead air.
Jerry
Jerry Avins
No engineer would design a 500 KW transmitter that would burn out 502.
Can you imagine a bus coming to a bridge so tightly rated that the
driver calls for three passengers to walk across after the bus makes the
far side in order not to overload the bridge? If you wanted to design a
bridge that would safely carry the unloaded bus but fail with the extra
three passengers on board, could you? TV transmitters have substantial
built-in safety factor.
Jerry Avins
...
> Its obvious that you've never built a TV station from the ground up.
> Even a spare 10% transmitter power capacity could cost a couple hundred
> thousand dollars in capital assets. and its unlikely the governing
> agency will allow you to use equipment capable of excess power, any more
> than you can build whatever tower height you want. It costs millions of
> dollars to build a full power commercial TV station.
You need to distinguish between rated capacity and transient overload
capacity.
My sewage plant is rated 20 million gallons a day. During periods of
heavy rain (and therefore groundwater infiltration) it regularly
processes 26 MGD without violating any discharge limits. After a few
days, however, effluent quality suffers.
Certain floors are required by code to carry 300 lb./sq.ft. If such a
floor fails catastrophically at 350 lb./sq.ft., the designer could well
lose his license.
Jerry Avins
Do we know that the final of a TV transmitter has the most dissipation
when it's outputting the most power? IIRC -- it was 1957 when I last had
to know -- those finals operate class B linear. Such amplifiers
experience maximum dissipation at well below full output.
J
Michael A. Terrell
Sure, but the backup was only intended for emergency operations. Some
AM stations operated at reduced power at night, so the secondary
transmitter shared both functions.
BTW, have you ever seen the pictures of the WLW 500 KW 700 KHz
transmitter in Cincinnati, Ohio? It also has one of the few remaining
Blaw Knox diamond towers.
http://hawkins.pair.com/wlw.shtml
I saw that transmitter around 1970, along with the bethany Ohio Voice
of America radio facility that was just down the road. The VOA station
is gone, torn down and turned into yet another golf course. :( It had
the original WWII Crosley transmitters when i toured it. The were being
replaced by custom designed transmitters built by National. They would
operate from the AM broadcast band, to 30 MHz, at any frequency in that
range. All of the transmitters were 50 KW, and could be run singly, in
pairs or whatever configuration they wanted. There was a huge, high
gain curtain antenna strung between three towers that fired East-West to
transmit to people behind the iron curtain. It would handle up to 500
kW from the ten transmitters one anything from one to ten frequencies at
once. I wasn't allowed to take any pictures, because it was a US
Government facility, and the military guards searched us for cameras
before we were allowed through the gates.
BobG
Eric Jacobsen
<mike.t...@earthlink.net> wrote:
>"Gene E. Bloch" wrote:
>>
>> > On 9/04/2007, Michael A. Terrell posted this:
>> >
>> > Its obvious that you've never built a TV station from the ground up.
>> > Even a spare 10% transmitter power capacity could cost a couple hundred
>> > thousand dollars in capital assets. and its unlikely the governing
>> > agency will allow you to use equipment capable of excess power, any more
>> > than you can build whatever tower height you want. It costs millions of
>> > dollars to build a full power commercial TV station.
>>
>> Do you *really* think I've never built a TV station from the ground up?
>>
>> Really?
>>
>> Well, you're correct.
>
>
> I HAVE built a complete TV station, starting with an empty building
>and no tower.
>
>
>> It doesn't keep from speculating, however.
>
>
> Speculate all you want, and let everyone see that you have absolutely
>no grasp of the subject.
>
>
>> For example, it *might* be true that it's a good idea to spend extra
>> money to put in safety factors (although, to be fair, I *do* run my
>> 100W lightbulbs at 100W). It could be cheaper in the long run than
>> fixing the reasult of not doing so.
>
>
> Do you know that a TV station's EIRP is transmitter power output,
>multiplied by antenna gain?
...less cable losses and backoff.
Cable loss is pretty substantial in most broadcast applications.
Nevertheless, transmitter headroom on broadcast amplifiers is pretty
expensive, as has been mentioned. So even getting a dB or two of
headroom can be not only a big NRE cost, but cost a lot of power
consumption during operation. The "black picture" thing is a real
concern in most NTSC transmitters, but it's pretty much just a typical
engineering concern of limiting the amount of black-picture time to
keep the thing from overheating or exceeding whatever spec is limited
by that particular design. And I've never run across an NTSC
transmitter, even a reasonably cheap one, that didn't have automatic
protection circuits that would keep the PA safe even if conditions
went wonky. i.e., it's tough to really damage one of those dude.
Not to say that I haven't done it. ;) A low-power NTSC transmitter
for which I used to be responsible went through a long string of PA
tubes, all covered by the manufacturer, before we figured out what was
wrong with it.
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
Martin Heffels
<mike.t...@earthlink.net> wrote:
> In the US a station has to notify the FCC if they are not operating
>at the power they are licensed for.
True, but §73.1560 of the FCC regulations says:
<quote>
(c) TV stations. (1) Except as provided in paragraph (d) of this section,
the visual output power of a TV or Class A TV transmitter, as determined by
the procedures specified in Sec. 73.664, must be maintained as near as is
practicable to the authorized transmitter output power and may not be less
than 80% nor more than 110% of the authorized power.
</quote>
So they could run at 80% theroretically, with the excuse that receivers
have improved, and people who live in the grade-B zones (or grade-Z ;-) ),
will probably have satellite-receivers by now anyway. Saving them a lot of
meny, and not actually violating the FCC-regulations.
Richard Owlett
NO WAY!!!
YOU claimed it was illegal to operate below rated power.
I challenged *YOU* to defend whacko claim!!!
Michael A. Terrell
The lowest power NTSC transmitter I ever used was a 90 Watt gates on
Ch 8 at an AFRTS TV station. It was a standby transmitter, but every
panel in it fit the exciter cabinet of the matching Gates main
transmitter. This was late '60s design, and I was using it in '73 &
'74. That station was intended to only cover the base. Some idiot ham
radio operator had the transmitter so screwed up, it wouldn't operate.
He was trying to tune it, like he did his beat up old Swan SSB mobile.
Both transmitters were damaged when i arrived. It took the better part
of a week to find the problems, only to discover that replacements for
the damaged parts had been ordered 18 months earlier and were still on
backorder. So they had 90 watts of Visual power, from the standby
transmitter and over 250 Watts of Aural power from the main
transmitter. I did some scrounging and found the needed parts and
repaired both transmitters. After a full alignment of the 500 W
transmitter, the output was 756 watts. I backed it down to an even 600
and ran it that way for the year I was in charge.
The biggest transmitter I maintained was a 130 KW Comark (Thales) on
Ch 55, with a 5 MW EIRP and a 1749 foot tower.
Martin Heffels
wrote:
>I challenged *YOU* to defend whacko claim!!!
Funny how every thread started by Radium, quickly turns into a slapfest.
-m-
stra...@yahoo.com
We were required to be between 80 and 110% of licensed power -
commercial low band VHF TV. Any deviation from that required log
entries for the day it happened. I'm not certain of the procedure if
it was going to be for any length of time but I'm certain there would
be exchanges with the local FCC office. As for a low power backup
transmitter, it was licensed at that power and certainly required log
entries when it is on line. If the main transmitter is going to be off
line for a while, I'm sure that would also require contact with the
FCC.
GG
Michael A. Terrell
>
> On Tue, 04 Sep 2007 12:56:25 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
>
> > In the US a station has to notify the FCC if they are not operating
> >at the power they are licensed for.
>
> True, but §73.1560 of the FCC regulations says:
>
> <quote>
> (c) TV stations. (1) Except as provided in paragraph (d) of this section,
> the visual output power of a TV or Class A TV transmitter, as determined by
> the procedures specified in Sec. 73.664, must be maintained as near as is
> practicable to the authorized transmitter output power and may not be less
> than 80% nor more than 110% of the authorized power.
> </quote>
Not one engineer worth his paycheck would try to run that close to
the bone. The 80% figure was the lower limit for aging final tubes. If
you were at 80% and the line voltage dropped a couple percent, you are
automatically operating out of spec. The 110% upper limit was to allow
for power line fluctuations in the other direction. Not many TV
transmitters were run from a Sola Adjust-A-Volt stepping regulator.
I kept to within +/- 3% of the rated power for civilian operations.
> So they could run at 80% theroretically, with the excuse that receivers
> have improved, and people who live in the grade-B zones (or grade-Z ;-) ),
> will probably have satellite-receivers by now anyway. Saving them a lot of
> meny, and not actually violating the FCC-regulations.
Theoretically, aliens could have built the station to be self
repairing, and powered it with a ZPM. TV is a competitive business, and
reducing power to save money is a sign they are going bankrupt. The 5
MW UHF station I engineered at paid out a little over $45,000 US dollars
a month to power the transmitter. that was less than half the monthly
operating budget for the station. if they wanted to save money, they
reduced the cost of heating and cooling the offices and studios, or laid
off a couple people, but they NEVER reduced power.
Michael A. Terrell
I don't chat with screaming idiots. Goodbye.
Michael A. Terrell
>
> On Tue, 04 Sep 2007 17:06:52 -0500, Richard Owlett <row...@atlascomm.net>
> wrote:
>
> >I challenged *YOU* to defend whacko claim!!!
>
> Funny how every thread started by Radium, quickly turns into a slapfest.
Hear that sound? I just flushed 'Slappy' down the toilet.
Don Bowey
Owlett" <row...@atlascomm.net> wrote:
As I recall all broadcast stations had to file a report if they needed to
run at reduced power.
Gene E. Bloch
> "Gene E. Bloch" wrote:
>>
>>> On 9/04/2007, Michael A. Terrell posted this:
>>>
>>> Its obvious that you've never built a TV station from the ground up.
>>> Even a spare 10% transmitter power capacity could cost a couple hundred
>>> thousand dollars in capital assets. and its unlikely the governing
>>> agency will allow you to use equipment capable of excess power, any more
>>> than you can build whatever tower height you want. It costs millions of
>>> dollars to build a full power commercial TV station.
>>
>> Do you *really* think I've never built a TV station from the ground up?
>>
>> Really?
>>
>> Well, you're correct.
> I HAVE built a complete TV station, starting with an empty building
> and no tower.
Immune to humor, are we?
<SNIP>
Gene E. Bloch
OK. So?
> Any system has to be designed with some sort of limits in mind.
I seem to have said that already.
> If the
> broadcasters want to make decisions about how much of a screen can be black
> and for how long, it's their decision to make.
Yes. They almost certainly would not follow my advice. In fact I'd
recommend *very* strongly that they ignore my advice :-)
glen herrmannsfeldt
(snip)
> Do we know that the final of a TV transmitter has the most dissipation
> when it's outputting the most power? IIRC -- it was 1957 when I last had
> to know -- those finals operate class B linear. Such amplifiers
> experience maximum dissipation at well below full output.
But with the sinc tips at peak output most of the signal will be
well below full output. That, and the sine shape should get close
to maximum dissipation at full output.
-- glen
stra...@yahoo.com
Where exactly _was_ the humor?
GG
Jerry Avins
> Martin Heffels wrote:
>> On Tue, 04 Sep 2007 17:06:52 -0500, Richard Owlett <row...@atlascomm.net>
>> wrote:
>>
>>> I challenged *YOU* to defend whacko claim!!!
>> Funny how every thread started by Radium, quickly turns into a slapfest.
>
>
> Hear that sound? I just flushed 'Slappy' down the toilet.
Question for the savvy: At what fraction of full output do ideal class A
and class B amplifiers sustain maximum internal dissipation? Hint:
blacker-than-black (synch level) is maximum output. Assuming that that
level is 100% modulation, the dissipation is then less than it is at
some lower level.
Jerry
Jerry Avins
The input to a class A amplifier doesn't depend on output power, so
dissipation is maximum at zero output and minimum at full. I leave it to
you to work out the maximum for an ideal class B. By ideal, I mean zero
voltage at maximum instantaneous current and double the supply rail
(inductive load) at zero current.
Jerry
Matt Ion
> Matt Ion wrote:
>> Richard Crowley wrote:
>>> "isw" wrote ...
>>>> Radium wrote:
>>>>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>>>>> monitors?
>>>> No. Prolonged blacks can damage television transmitters, however (video
>>>> is inverted for transmission, so black requires full power from the
>>>> transmitter).
>>>
>>> Prolonged bright areas (whether clipped or not) will damage CRT
>>> monitors. I have two on the bench right now to have their CRTs
>>> replaced because the image is burned-in. They came from a
>>> security/survelience application and you can somewhat see the
>>> hallway and the doors they were monitoring.
>>
>> ANY static image for a prolonged time will cause burn-in on a CRT or
>> plasma display. The brighter it is, the less time it takes, but it
>> doesn't have to be pure white for burn to occur. Simply displaying
>> 100% white won't cause instant death of a monitor, however, the way a
>> clipped signal can damage a speaker.
>
> Speaker damage occurs when the *speaker* clips.
You're right, of course... poor wording on my part.
isw
"Michael A. Terrell" <mike.t...@earthlink.net> wrote:
> isw wrote:
> >
> > In article <1188874984.2...@y42g2000hsy.googlegroups.com>,
> > Radium <gluc...@gmail.com> wrote:
> >
> > > Hi:
> > >
> > > Clipping in an audio signal results when an audio device receives a
> > > signal that is too loud. The audio signal distorts into square-waves
> > > because the "tops" of the signal are flattened. The device cannot
> > > handle power levels over a certain level. When this level is exceeded,
> > > clipping occurs. Clipping is usually harsher in digital devices than
> > > in analog devices. Analog clipping tends to be fuzzy and soft compared
> > > to digital clipping.
> > >
> > > What is the visual-equivalent of "clipping"? Is there a difference
> > > between analog and digital in terms of visual-clipping? If so, what is
> > > the difference?
> >
> > Clipping causes whites lose all texture -- very similar to overexposed
> > film.
> >
> > > Auditory-clipping can damage speakers. Can visual-"clipping" damage
> > > monitors?
> >
> > No. Prolonged blacks can damage television transmitters, however (video
> > is inverted for transmission, so black requires full power from the
> > transmitter).
> >
> > Isaac
>
>
>
> No, only the sync tips are at 100%.
Picky, picky.
Yeah, but by themselves, they represent a fairly low duty cycle; plus,
of course, the transmitter expects sync pulses. A black image is
"nearly" full power all the time. It's the high average that kills the
transmitter finals.
Isaac
isw
Martin Heffels <goo...@flikken.net> wrote:
> On Mon, 03 Sep 2007 20:27:43 -0700, isw <i...@witzend.com> wrote:
>
> >Clipping causes whites lose all texture -- very similar to overexposed
> >film.
>
> White clipping makes you loose the texture, and some other interesting
> things occur, like the clipped area turning yellowish (solarization).
> But it's not only white which can clip, with colour-correction you can
> easily clip one of the three colour-channels. And of course you can clip
> black as well, loosing shadow detail.
>
> >> Auditory-clipping can damage speakers. Can visual-"clipping" damage
> >> monitors?
> >
> >No. Prolonged blacks can damage television transmitters, however (video
> >is inverted for transmission, so black requires full power from the
> >transmitter).
>
> I would say the transmitters would be resistant to that. Most run below
> their designed maximum power anyway.
Well, when I was in the business, ten seconds of black would *guarantee*
a phone call from a very irate chief engineer, from whose budget the
replacement final amplifiers would be purchased.
Isaac
Michael A. Terrell
>
> On 9/04/2007, Michael A. Terrell posted this:
> > "Gene E. Bloch" wrote:
> >>
> >>> On 9/04/2007, Michael A. Terrell posted this:
> >>>
> >>> Its obvious that you've never built a TV station from the ground up.
> >>> Even a spare 10% transmitter power capacity could cost a couple hundred
> >>> thousand dollars in capital assets. and its unlikely the governing
> >>> agency will allow you to use equipment capable of excess power, any more
> >>> than you can build whatever tower height you want. It costs millions of
> >>> dollars to build a full power commercial TV station.
> >>
> >> Do you *really* think I've never built a TV station from the ground up?
> >>
> >> Really?
> >>
> >> Well, you're correct.
>
> > I HAVE built a complete TV station, starting with an empty building
> > and no tower.
>
> Immune to humor, are we?
No, I'm not, but I saw no humor in your posts. There is enough
misinformation posted on tech newsgroups, and too many idiots that will
believe it.
Michael A. Terrell
>
> Michael A. Terrell wrote:
> > Martin Heffels wrote:
> >> On Tue, 04 Sep 2007 17:06:52 -0500, Richard Owlett <row...@atlascomm.net>
> >> wrote:
> >>
> >>> I challenged *YOU* to defend whacko claim!!!
> >> Funny how every thread started by Radium, quickly turns into a slapfest.
> >
> >
> > Hear that sound? I just flushed 'Slappy' down the toilet.
>
> Question for the savvy: At what fraction of full output do ideal class A
> and class B amplifiers sustain maximum internal dissipation? Hint:
> blacker-than-black (synch level) is maximum output. Assuming that that
> level is 100% modulation, the dissipation is then less than it is at
> some lower level.
http://download.harris.com/app/public_download.asp?fid=723
Harris used to have a lot more information on analog TV transmission,
but they have been replaced with subjects dealing with digital TV.
Michael A. Terrell
That's what I stated in another post.
If the problems persisted, the FCC would step in and decided if the
station could stay on the air. It is like the C.P. phase, where you
have a set time to build the station and pass the initial proof of
performance. If you are not ready on time, you MIGHT get an extension.
RF allocations are considered assets, and if you mishandle them, you
lose them.
I left the business 10 years ago, but a friend that was still doing
contract broadcast engineering was always calling to let me know the
latest fiasco that some station was trying to cover up. Several
stations have gone dark, and lost their license because they were too
cheap to maintain critical equipment, and the FCC stepped in. Add the
cost of fines to bringing a station up to specs, and fly by night owners
just pull the plug. Some are so run down that they can't even sell any
equipment.
I was in Ft. Walton Beach, Florida when their AM rock station pulled
the plug. I was building WRMX, Ch 58 in Destin at the time, and drove
over to see what equipment they had. They tried to tell me that they
had sold their 35 year old AM transmitter for $25K, and had an offer of
$50K for the rest of the equipment, which was two turntables, three cart
machines an eight channel board and one microphone. I've seen better
equipment, in better condition tossed in the trash, after a large
hamfest. I told the chief engineer of Ch 35 in Ft Walton Beach about
their delusional claims, and we both had a good laugh.
Their tower was cheap guyed home TV antenna tower with three pieces
of 8 AWG bare copper run down the legs because the joints were rusting
out. That tower probably cost less than $750 to buy and put up when it
was new. From the looks of the station, they spent less than $5k on
equipment when they built the mess.
Mr.T
"Battleax" <unava...@thistime.net> wrote in message
news:a962d$46dd4827$d1d94bc8$27...@PRIMUS.CA...
> Radium seems to be a good example of mental clipping. Brain attempting to
> think far beyond it's capacity
Given that capacity is so close to zero, then it seems inevitable :-)
MrT.
Donald Reay
> No engineer would design a 500 KW transmitter that would burn out 502.
> Can you imagine a bus coming to a bridge so tightly rated that the
> driver calls for three passengers to walk across after the bus makes the
> far side in order not to overload the bridge? If you wanted to design a
> bridge that would safely carry the unloaded bus but fail with the extra
> three passengers on board, could you? TV transmitters have substantial
> built-in safety factor.
I once arrived at the airport well before the departure of the flight
I was booked on and was denied a seat on an earlier flight. The reason
given was the load that the aircraft could safely carry. I was told
that either I (150lbs) or my luggage (25lbs) but not both could travel
on the earlier flight.
PS I do realise that they were basically telling me to £%*& off!
Martin Heffels
>I once arrived at the airport well before the departure of the flight
>I was booked on and was denied a seat on an earlier flight. The reason
>given was the load that the aircraft could safely carry. I was told
>that either I (150lbs) or my luggage (25lbs) but not both could travel
>on the earlier flight.
>
>PS I do realise that they were basically telling me to £%*& off!
It's getting quite OT now, but you should try inter-island flights in for
instance Tonga. You and your luggage get weighed, and if the plane gets too
heavy, you can choose which to go first to the net island (better to travel
on the Orange Vomit there ;-) ).
cheers
-martin-
Arny Krueger
"Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
news:46DD95F2...@earthlink.net...
> Its obvious that you've never built a TV station from the ground up.
> Even a spare 10% transmitter power capacity could cost a couple hundred
> thousand dollars in capital assets. and its unlikely the governing
> agency will allow you to use equipment capable of excess power, any more
> than you can build whatever tower height you want. It costs millions of
> dollars to build a full power commercial TV station.
Agreed. Of course some reserve capacity is built in so that the equipment
lasts under normal use. It just might not take the form of vastly increased
steady-state capacity.
I may have missed this when it was covered elsewhere:
Is there anything in the signal chain besides humans that keeps a commercial
TV station from broadcasting pure black video for an indefinate period of
time?
Bob Myers
has actually answered our boy Radium's original question,
which had to do with VISUAL clipping. Everyone's been
talking about what happens when a video signal is clipped,
or when a video transmitter overloads, but the way Radium
asked the question, I can only assume he's worried about
what happens when you shine a really bright light into your
eyes.....;-)
Bob M.
Martin Heffels
<nospam...@address.invalid> wrote:
>I can only assume he's worried about
>what happens when you shine a really bright light into your
>eyes.....;-)
I suggest that Radium has a 5 minute look into the sun with bare eyes.
That should give a good hint what will happen.
-m-
glen herrmannsfeldt
(snip)
> Question for the savvy: At what fraction of full output do ideal class A
> and class B amplifiers sustain maximum internal dissipation? Hint:
> blacker-than-black (synch level) is maximum output. Assuming that that
> level is 100% modulation, the dissipation is then less than it is at
> some lower level.
For a class B amplifier, instantaneous maximum dissipation is at half
the maximum output. Averaged over a sine, it is at 2/pi of a
maximum amplitude sine.
For NTSC video, with sinc at 100%, black at 92.5%, and white at 0%,
it would seem that 50% is 42.5/92.5 of the way from black to white,
or about 46% gray.
http://www.maxim-ic.com/appnotes.cfm/an_pk/734
(The first google hits for "sync tips" are related to PDAs.)
-- glen
Michael A. Terrell
>
> "Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
> news:46DD95F2...@earthlink.net...
>
> > Its obvious that you've never built a TV station from the ground up.
> > Even a spare 10% transmitter power capacity could cost a couple hundred
> > thousand dollars in capital assets. and its unlikely the governing
> > agency will allow you to use equipment capable of excess power, any more
> > than you can build whatever tower height you want. It costs millions of
> > dollars to build a full power commercial TV station.
>
> Agreed. Of course some reserve capacity is built in so that the equipment
> lasts under normal use. It just might not take the form of vastly increased
> steady-state capacity.
No one in their right mind would build a transmitter with every
component pushed to the limit. It would fail daily. The goal is to
reduce downtime to scheduled maintenance periods. To reduce that to
cleaning of air filters, and annual flush of the cooling system, other
than the occasional rebuild of a final tube. The new Harris High power
solid state TV transmitters are modular, so that a bad RF tray can be
replaced without going off the air. I haven't seen the solid state TV
transmitter in person, but I have seen several 5 KW Harris SS AM
transmitters, and the damage lightening can do when a tower is hit.
> I may have missed this when it was covered elsewhere:
>
> Is there anything in the signal chain besides humans that keeps a commercial
> TV station from broadcasting pure black video for an indefinate period of
> time?
I have seen TV stations transmit a 1 KHz tone and black for over a
half hour during weekly maintenance. If the transmitter can handle
that, it can handle anything.
Michael A. Terrell
I never see his posts, because Supernews drops massively cross posted
messages from 'Google Groups', and I'm not going to waste time looking
them up on GG..
Gene E. Bloch
Gene E. Bloch
> "Gene E. Bloch" wrote:
>>
>> On 9/04/2007, Michael A. Terrell posted this:
>>> "Gene E. Bloch" wrote:
>>>>
>>>>> On 9/04/2007, Michael A. Terrell posted this:
>>>>>
>>>>> Its obvious that you've never built a TV station from the ground up.
>>>>> Even a spare 10% transmitter power capacity could cost a couple hundred
>>>>> thousand dollars in capital assets. and its unlikely the governing
>>>>> agency will allow you to use equipment capable of excess power, any more
>>>>> than you can build whatever tower height you want. It costs millions of
>>>>> dollars to build a full power commercial TV station.
>>>>
>>>> Do you *really* think I've never built a TV station from the ground up?
>>>>
>>>> Really?
>>>>
>>>> Well, you're correct.
>>
>>> I HAVE built a complete TV station, starting with an empty building
>>> and no tower.
>>
>> Immune to humor, are we?
>
>
> No, I'm not, but I saw no humor in your posts. There is enough
> misinformation posted on tech newsgroups, and too many idiots that will
> believe it.
QED
glen herrmannsfeldt
If it is bright enough, you will get to the non-linear region
of the sensing dyes and sense the harmonics of the light
source. Non-linear optics is a big field.
-- glen
dizzy
>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>> monitors?
>
>In general, audio clipping does not damage speakers. The usual
>case that causes damage is the combination of a few things:
>
>Using multiple drivers to cover a large frequency range, with
>a crossover network to divide up the signal.
>
>Musical audio has much more power at lower frequencies than higher
>frequencies, so speakers are designed appropriately.
>
>Clipping generates a lot of power at the higher harmonics of the
>input frequencies that goes to drivers not designed for
>those power levels.
>
>In most video systems this combination doesn't exist. It might
>in future video reproduction systems, though.
This is the correct answer, that everyone else missed.
Jerry Avins
...
> I have seen TV stations transmit a 1 KHz tone and black for over a
> half hour during weekly maintenance. If the transmitter can handle
> that, it can handle anything.
Why the emphasis on black level? Maximum internal dissipation peaks at a
power output less than maximum for all linear amplifiers. The input
power of a class A amplifier is independent of output, so maximum power
output corresponds to minimum dissipation.
Richard Crowley
> Michael A. Terrell wrote:
>> I have seen TV stations transmit a 1 KHz tone and black for over a
>> half hour during weekly maintenance. If the transmitter can handle
>> that, it can handle anything.
>
> Why the emphasis on black level? Maximum internal dissipation peaks at a
> power output less than maximum for all linear amplifiers. The input power
> of a class A amplifier is independent of output, so maximum power output
> corresponds to minimum dissipation.
But: 1) it *is* a linear system and maximum amplitude still stresses
the amplifiers, etc. and 2) maximum amplitude also stresses the
downstream circuit: waveguide, switches, impedance matching and
phasing circuits, and even antennas. Remembering that the visual
signal is AM. OTOH, the aural signal is FM and should be running
at a constant amplitude/power regardless of modulation (or not).
Arny Krueger
"glen herrmannsfeldt" <g...@ugcs.caltech.edu> wrote in message
news:I9ydnaAys6XypEDb...@comcast.com...
> Musical audio has much more power at lower frequencies than higher
> frequencies, so speakers are designed appropriately.
So far so good.
> Clipping generates a lot of power at the higher harmonics of the
> input frequencies that goes to drivers not designed for
> those power levels.
Actually, when you clip a sine wave you get a square wave. It only has odd
harmonics and the amplitude of the harmonics is inversely proportional to
frequency. This is actually quite a rapid roll-off. Most music has an
energy distribution that is far more taxing to the upper range drivers.
Clipping is a way for an amplifier to continue to provide increasing amounts
of power to a speaker as the input increases, even though the amplifier has
reached its voltage and/or current limits on the peaks. It is usually
simply the additional power that breaks the drivers.
Jerry Avins
Do you mean that the waveguide or transmission cable is the weak link in
the transmitter? Somehow, I don't think so. Maximum output indeed
stresses the system, but somewhat less than maximum stresses the output
stage more. The math is pretty simple.
Mr.T
"Arny Krueger" <ar...@hotpop.com> wrote in message
news:1ZOdncMIyMyQbULb...@comcast.com...
> > Clipping generates a lot of power at the higher harmonics of the
> > input frequencies that goes to drivers not designed for
> > those power levels.
A common misconception for a simple overloading problem.
> Actually, when you clip a sine wave you get a square wave.
Actually you get a clipped sine wave, it will not have the straight sides of
a square wave.
Only if the clipping is astronomically severe will it approach a true square
wave.
> It only has odd harmonics
True for a square wave, not quite so true for a clipped sine wave.
> Clipping is a way for an amplifier to continue to provide increasing
amounts
> of power to a speaker as the input increases, even though the amplifier
has
> reached its voltage and/or current limits on the peaks. It is usually
> simply the additional power that breaks the drivers.
Agreed.
MrT.
Al in Dallas
wrote:
>On 9/3/07 9:07 PM, in article
>1188878846....@d55g2000hsg.googlegroups.com, "Radium"
><gluc...@gmail.com> wrote:
>
>> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
>>
>snip
>>
>>> No. Prolonged blacks can damage television transmitters, however (video
>>> is inverted for transmission, so black requires full power from the
>>> transmitter).
>>
>> Prolonged black can damage a monitor/screen? That's weird. White is
>> analogous to the loudest sound a loudspeaker can playback. Black is
>> analogous to a loudspeaker not being feed any signal.
>
>snip
>
>More Trolling.
>
>Exactly where did he say prolonged black can damage a monitor/screen
But is it trolling or is Radium just inattentive to details because
he's too excited about the conversation?
--
Al in St. Lou
Al in Dallas
<spam...@nobody.invalid> wrote:
>On 9/04/2007, Michael A. Terrell posted this:
>> "Gene E. Bloch" wrote:
>>>
>>> On 9/04/2007, Michael A. Terrell posted this:
>>>> "Gene E. Bloch" wrote:
>>>>>
>>>>>> On 9/04/2007, Michael A. Terrell posted this:
>>>>>>
>>>>>> Its obvious that you've never built a TV station from the ground up.
>>>>>> Even a spare 10% transmitter power capacity could cost a couple hundred
>>>>>> thousand dollars in capital assets. and its unlikely the governing
>>>>>> agency will allow you to use equipment capable of excess power, any more
>>>>>> than you can build whatever tower height you want. It costs millions of
>>>>>> dollars to build a full power commercial TV station.
>>>>>
>>>>> Do you *really* think I've never built a TV station from the ground up?
>>>>>
>>>>> Really?
>>>>>
>>>>> Well, you're correct.
>>>
>>>> I HAVE built a complete TV station, starting with an empty building
>>>> and no tower.
>>>
>>> Immune to humor, are we?
>>
>>
>> No, I'm not, but I saw no humor in your posts. There is enough
>> misinformation posted on tech newsgroups, and too many idiots that will
>> believe it.
>
>QED
I've been an engineer for 25 years. Many of my colleagues have lacked
much in the way of a normal sense of humor. Non-engineers seem to rate
us as second place for being strange, overly literal, and humorless.
Accountants take first place.
The engineering student went home for vacation to his rural town. When
relatives insisted on an example of what he'd learned, he said
"pi-R-squared." Someone replied, "Gah, you got that wrong; cornbread
are square; pie are round!"
Michael A. Terrell
>
> I've been an engineer for 25 years. Many of my colleagues have lacked
> much in the way of a normal sense of humor. Non-engineers seem to rate
> us as second place for being strange, overly literal, and humorless.
> Accountants take first place.
Al, the uninformed just don't get our humor, even if we try to
explain it to them. I was an engineer at an AFRTS TV station at Ft
Greely in the '70s. I had a problem with a couple of the talking heads
on our live newscast. They wouldn't stay in their seats, or even on set
during actualities, so I rewired their off air monitor. The next
newscast they got up and were shadow boxing in front of the news desk
when the sound went dead, and they thought that they were on air, in
their dress uniform jackets, and underwear. (No air conditioning at the
station). Needless to say, they freaked out! The next time they got
out of line was a Saturday noon newscast, where a fishing program from a
station in Fairbanks was on their off air monitors. :)
My best pranks at the station? One of the staff was a drunk and he
was always bragging that he was too smart to get caught. The late night
DJ had relatives that worked at a NOAA weather station nearby, and a lot
of nights they would bring him supper. They had brought the bottle with
the food, and it might have had a quarter of a cup. I was going to make
a bank out of the bottle, but I couldn't carry it back to the barracks
that night, so I hid the empty wine bottle inside the console, behind a
rack mount CCU power supply. The station manager found it, and raised
bloody hell. The guy drank so much that he truly couldn't remember if
it was his bottle, so I just stood back and enjoyed the floor show.
before it was over, he admitted to drinking on duty, and apologized for
leaving the empty bottle. The manager pulled him from engineering
rotation, then put him on day shift in the film library.
Another time we had a general from the Pentagon visiting the base. He
called the station and didn't identify himself. He ordered me to run
something else, because he had seen the movie the week before, in DC. I
replied, Sorry sir, but I haven't seen it, and hung up. He called right
back, and started yelling that he was a general, and that if I didn't
obey his order, he was calling my commanding general. I laughed and
said, "Tell him that Michael said 'Hello'." He snarled "What the hell
does that mean?" I laughed and told him, "My General will explain it to
you, if you're stupid enough to call him". He proceeded to brag about
all his friends in DC, so I reminded him that he wasn't in DC, but at
the US Army cold weather test site, 105 miles from the nearest real
town. Then I told him all the places that I had friends. He grumbled,
"One damn phone call and I'm out of here!" I asked him how he would
find a working outside phone line, or mail a letter if word spread that
he was trying to disrupt our only entertainment. Then I twisted the
knife a little more and said, In fact, if you piss off the wrong people,
they will lose your orders, and report you as AWOL and last seen heading
for the Bering Straits, and Russia. Your Pentagon friends wouldn't help
you if they think you're a commie, will they? He never called back.
Was it something I said? ;-)
My all time favorite was running a station ID in color, on a B&W only
'60 RCA and Gates plant. The Base Information Officer was telling
everyone that the station could not be converted to color. I don't know
about you, but I have never let the 'unwashed' tell me what I CAN'T do.
I borrowed a Heathkit color bar generator, made a custom 35 mm ID slide
with parts from the slide repair kit, and dry transfer lettering from
the leftover bin in the newspaper office. I used the very basic video
keyer in the '60 vintage RCA video switcher to invert the video from the
film chain to display:
AFRTS
CH8
in bold colors on a black background. Boy, did the excrement hit the
rotary oscillator! The shit hit the fan, too! ;-)
Five seconds later, the control room's private phone line was
ringing. The base information officer was screaming, "Soldier, you've
just made a fool of me!" I replied, "But Sir!, You've always bragged of
being a self made man!". He never spoke to me again, or bothered
anything in the radio or TV station. I know he called my commanding
general, and was told to leave me alone, and stay out of the transmitter
and control room, for his own good. :)
I had an ongoing problem with the base power plant. They
intentionally caused brownouts, and used us as a power dump. I was less
than five minutes into the first of three reels of kinescope of the '74
world series when my line voltage dropped from 120 VAC to 25 VAC, shot
up over 210 VAC (the upper limit of the AC line meter), and was tripping
circuit breakers all over the complex. That was the final straw! After
I picked up all the pieces of shredded film, I had one of the DJs cut a
custom 30 second cart with "AFRTS CH8 will return to the air as soon as
the AC power problems are resolved. If you have any questions call:
XXX-XXXX" The phone number was an unlisted line into the power plat
manager's office. He got several *hundred* phone calls, and I never saw
the line voltage vary more than 5 volts after that. ;-)
In spite of all this, I had turned a station that could barely sign
on each day, into one that ran over seven months without an on air
failure. I made E4 at around 20 months and received a letter of
commendation from my commanding General.
A few weeks after I left that station, the two chief engineers from
the Fairbanks TV stations paid a visit to "Help out the poor dumb GIs at
that crappy little military TV station" They were pissed off at how
well the station was running, and admitted to the other engineer that it
was in better shape that either of their stations. My friend Neeley "The
Hoop" asked them, "Do you remember the soldier that you refused to give
the nickel tour of your stations"? He did all the work.
Michael A. Terrell
>
> Richard Crowley wrote:
> > "Jerry Avins" wrote ...
> >> Michael A. Terrell wrote:
> >>> I have seen TV stations transmit a 1 KHz tone and black for over a
> >>> half hour during weekly maintenance. If the transmitter can handle
> >>> that, it can handle anything.
>
> >> Why the emphasis on black level? Maximum internal dissipation peaks at a
> >> power output less than maximum for all linear amplifiers. The input power
> >> of a class A amplifier is independent of output, so maximum power output
> >> corresponds to minimum dissipation.
> >
> > But: 1) it *is* a linear system and maximum amplitude still stresses
> > the amplifiers, etc. and 2) maximum amplitude also stresses the
> > downstream circuit: waveguide, switches, impedance matching and
> > phasing circuits, and even antennas. Remembering that the visual
> > signal is AM. OTOH, the aural signal is FM and should be running
> > at a constant amplitude/power regardless of modulation (or not).
>
> Do you mean that the waveguide or transmission cable is the weak link in
> the transmitter? Somehow, I don't think so. Maximum output indeed
> stresses the system, but somewhat less than maximum stresses the output
> stage more. The math is pretty simple.
No, unless the waveguide is damaged. A tower worker found a hairline
crack in our waveguide when he leaned against the corner, and received a
six inch long RF burn. We had a slow nitrogen leak we couldn't find,
but he did. The crack was invisible, but it cause the pressure to
change, with temperature. There was approx. 195 KW of UHF RF in that
rectangular waveguide, all 1800 feet of it. If the pressure was low, it
changed the dielectric characteristics, which caused sync clipping.
Matt Ion
> Five seconds later, the control room's private phone line was
> ringing. The base information officer was screaming, "Soldier, you've
> just made a fool of me!" I replied, "But Sir!, You've always bragged of
> being a self made man!". He never spoke to me again, or bothered
> anything in the radio or TV station.
Now THAT is CLASSIC! :)
Jerry Avins
Just curious: how did you fix it?
Michael A. Terrell
Its too bad that I STILL can't tell the really good stories. :(
Michael A. Terrell
>
> Michael A. Terrell wrote:
> >
> > crack in our waveguide when he leaned against the corner, and received a
> > six inch long RF burn. We had a slow nitrogen leak we couldn't find,
> > but he did. The crack was invisible, but it cause the pressure to
> > change, with temperature. There was approx. 195 KW of UHF RF in that
> > rectangular waveguide, all 1800 feet of it. If the pressure was low, it
> > changed the dielectric characteristics, which caused sync clipping.
>
> Just curious: how did you fix it?
"I" didn't. The defect was about 1000 feet above ground, and was
probably damaged when they worked on the FM curtain antenna for five of
the 'Orlando' FM radio stations.
The waveguide was custom made and under warranty, so the OEM had to
build and ship a replacement. The tower crew was called to replace it,
then the defective brass was shipped back for their inspection, and to
be scrapped. The same guy was on the second crew and had no trouble
remembering the spot where he got a second degree burn on his ass, so it
didn't take very long to swap out. Remove all the flange bolts, free up
the hanger hardware and slide it out. CAREFUlLY slip the new piece into
place and replace all the brass bolds. They did it one Sunday night
between midnight and 6:00 AM when the transmitter was off line for
weekly maintenance. The Chief engineer was there that night, instead of
me. The next weekend it was time to flush the coolant, and replace it
so four of us worked our asses off to drain the system, clean it, flush
it twice, then refill it with distilled water and antifreeze. It took
almost seven hours so we were late signing on, Monday morning. The rest
of the week it was in operation 24/7.
Matt Ion
> Jerry Avins wrote:
>> Michael A. Terrell wrote:
>>> No, unless the waveguide is damaged. A tower worker found a hairline
>>> crack in our waveguide when he leaned against the corner, and received a
>>> six inch long RF burn. We had a slow nitrogen leak we couldn't find,
>>> but he did. The crack was invisible, but it cause the pressure to
>>> change, with temperature. There was approx. 195 KW of UHF RF in that
>>> rectangular waveguide, all 1800 feet of it. If the pressure was low, it
>>> changed the dielectric characteristics, which caused sync clipping.
>> Just curious: how did you fix it?
Duct tape, of course :)
> then the defective brass was shipped back for their inspection,
Would that defective brass be the aforementioned "self-made" officer?
Hehehehe!
dmaster
> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
>
> > Radium <gluceg...@gmail.com> wrote:
> > > Hi:
> > > Clipping in an audio signal results when an audio device receives a
> > > signal that is too loud. The audio signal distorts into square-waves
> > > because the "tops" of the signal are flattened. The device cannot
> > > handle power levels over a certain level. When this level is exceeded,
> > > clipping occurs. Clipping is usually harsher in digital devices than
> > > in analog devices. Analog clipping tends to be fuzzy and soft compared
> > > to digital clipping.
> > > What is the visual-equivalent of "clipping"? Is there a difference
> > > between analog and digital in terms of visual-clipping? If so, what is
> > > the difference?
The similarity is probably in the realm of "loss of information". The
difference is that the speaker system you are probably thinking about
receives both frequency (which sound) and power from an external
source: your amplifier. In video systems, no "power" is delivered to
the display device; only information that defines the color and
brightness.
> > Clipping causes whites lose all texture -- very similar to overexposed
> > film.
>
> What does this look like on a screen?
Simple: at the white end, near whites all become white. At the black
end, near blacks all become black. The result is loss of detail.
Near white areas look like a single patch of white with no detail.
Near black areas look like a single patch of black with no detail.
>
> > > Auditory-clipping can damage speakers. Can visual-"clipping" damage
> > > monitors?
No. While long term display of the *same* image can damage some
monitor technologies, there is no picture/color you can display that
can damage the display device.
> > No. Prolonged blacks can damage television transmitters, however (video
> > is inverted for transmission, so black requires full power from the
> > transmitter).
>
> Prolonged black can damage a monitor/screen? That's weird. White is
> analogous to the loudest sound a loudspeaker can playback. Black is
> analogous to a loudspeaker not being feed any signal.
>
> When the power-supply of the monitor/screen is turned off, the monitor/
> screen is black because it not receiving any voltage.
>
> I would think that extremely-bright white would damage the screen
> because the brightest white results from the highest voltage applied
> to the Reds, Greens, and Blues [equal intensities of R, G, & B -- if
> combined -- appear white to our eyes when emitted by an electronic
> monitor] in a particular area of the monitor/screen. If the voltage
> exceeds this for prolonged periods of time, that region of the screen
> will burn out, much like forcing an extremely-high voltage audio
> signal into a speaker will cause the speaker to short-circuit and the
> diaphragm to pop and/or melt. Many instructions manual for speakers
> give direction not to reach or go above the clipping point and
> clipping damages the speakers. Wouldn't something similar happen to a
> monitor/screen [whether it's a CRT, plasma, or LCD] if it was forced
> to display light-intensities beyond its limits?
No, because the "amplifier" is integral to the display and won't
produce something which would damage the display device. (You need to
learn something about display technologies.) Let's just look at LCDs
(each technology is unique so you'll need to read about the others).
An LCD display can be thought of a large array of red, green, and blue
doors in front of a light bulb. The light bulb is always on. The
video signal tells the display which of the red/green/blue doors to
open at each location on the screen. If all three doors are open, the
white light from the bulb is visible. If only the red door is
*closed*, the light is colored red. If all three doors are closed,
the light is blocked and the location looks black. There is no such
thing as "too much light" because the information source doesn't
control the light bulb, only the doors.
Dan (Woj...)
Michael A. Terrell
>
> Michael A. Terrell wrote:
> > Jerry Avins wrote:
> >> Michael A. Terrell wrote:
> >>> No, unless the waveguide is damaged. A tower worker found a hairline
> >>> crack in our waveguide when he leaned against the corner, and received a
> >>> six inch long RF burn. We had a slow nitrogen leak we couldn't find,
> >>> but he did. The crack was invisible, but it cause the pressure to
> >>> change, with temperature. There was approx. 195 KW of UHF RF in that
> >>> rectangular waveguide, all 1800 feet of it. If the pressure was low, it
> >>> changed the dielectric characteristics, which caused sync clipping.
> >> Just curious: how did you fix it?
>
> Duct tape, of course :)
You never use duct tape on a tower. It holds moisture, which leads
to rust, then to a tower collapse.
> > then the defective brass was shipped back for their inspection,
>
> Would that defective brass be the aforementioned "self-made" officer?
> Hehehehe!
No, he was in Alaska, the bad waveguide was near Daytona Beach,
Florida
Jerry Avins
> Matt Ion wrote:
>> Michael A. Terrell wrote:
>>> Jerry Avins wrote:
>>>> Michael A. Terrell wrote:
>>>>> No, unless the waveguide is damaged. A tower worker found a hairline
>>>>> crack in our waveguide when he leaned against the corner, and received a
>>>>> six inch long RF burn. We had a slow nitrogen leak we couldn't find,
>>>>> but he did. The crack was invisible, but it cause the pressure to
>>>>> change, with temperature. There was approx. 195 KW of UHF RF in that
>>>>> rectangular waveguide, all 1800 feet of it. If the pressure was low, it
>>>>> changed the dielectric characteristics, which caused sync clipping.
>>>> Just curious: how did you fix it?
>> Duct tape, of course :)
>
>
> You never use duct tape on a tower. It holds moisture, which leads
> to rust, then to a tower collapse.
I once patched a waveguide with an acetylene torch, borax, and a piece
of low-melting (silver-bearing) brass. I'm sure it played havoc with the
internal silver plating, but that's life, one does what one can. Of
course, X-band guide is easier to heat locally that TV guide.
Michael A. Terrell
>
> I once patched a waveguide with an acetylene torch, borax, and a piece
> of low-melting (silver-bearing) brass. I'm sure it played havoc with the
> internal silver plating, but that's life, one does what one can. Of
> course, X-band guide is easier to heat locally that TV guide.
This was at least 1/4" brass plate, so the torch would have likely
burnt a hole before brazing properly. If the weld isn't clean on the
inside, it will turn a lot of RF into heat. That is probably what
cracked the weld in the first place. A tiny bit of flux, or oxide that
didn't burn away during the machine welding process. Imagine something
stuck into a 195 KW microwave oven. :)
Jerry Avins
> Jerry Avins wrote:
>> I once patched a waveguide with an acetylene torch, borax, and a piece
>> of low-melting (silver-bearing) brass. I'm sure it played havoc with the
>> internal silver plating, but that's life, one does what one can. Of
>> course, X-band guide is easier to heat locally that TV guide.
>
>
> This was at least 1/4" brass plate, so the torch would have likely
> burnt a hole before brazing properly. If the weld isn't clean on the
> inside, it will turn a lot of RF into heat. That is probably what
> cracked the weld in the first place. A tiny bit of flux, or oxide that
> didn't burn away during the machine welding process. Imagine something
> stuck into a 195 KW microwave oven. :)
You don't burn holes before a lower-melting brass liquefies. I wrote
"acetylene" -- Prestolite -- not oxycetylene. Brass is what is called
"hot short", i.e., more brittle hot than cold. The wetting ability of
some brazing rod is amazing. I have seen it wick through and along
cracks that weren't noticed on casual inspection. (But I wouldn't depend
on it.)
Apropos nothing: There are some pretty marvelous alloys around.
Cerrosafe melts at a low enough temperature (165F) so that you can, with
some discomfort, hold a puddle in the palm of your hand. It shrinks upon
solidifying to facilitate removal from the mold, then expands at room
temperature to exactly the size of the mold it froze in. Gunsmiths use
it to gauge size and roundness of cartridge chambers. Ain't technology
grand?
Michael A. Terrell
>
> Michael A. Terrell wrote:
> > Jerry Avins wrote:
> >> I once patched a waveguide with an acetylene torch, borax, and a piece
> >> of low-melting (silver-bearing) brass. I'm sure it played havoc with the
> >> internal silver plating, but that's life, one does what one can. Of
> >> course, X-band guide is easier to heat locally that TV guide.
> >
> >
> > This was at least 1/4" brass plate, so the torch would have likely
> > burnt a hole before brazing properly. If the weld isn't clean on the
> > inside, it will turn a lot of RF into heat. That is probably what
> > cracked the weld in the first place. A tiny bit of flux, or oxide that
> > didn't burn away during the machine welding process. Imagine something
> > stuck into a 195 KW microwave oven. :)
>
> You don't burn holes before a lower-melting brass liquefies. I wrote
> "acetylene" -- Prestolite -- not oxycetylene. Brass is what is called
> "hot short", i.e., more brittle hot than cold. The wetting ability of
> some brazing rod is amazing. I have seen it wick through and along
> cracks that weren't noticed on casual inspection. (But I wouldn't depend
> on it.)
How do you propose to control what flows into the waveguide? I have
never heard of anyone even attempting to repair high power waveguide in
the field. Also, since it is pressurized, what is to stop you from
making the crack worse?
>
> Apropos nothing: There are some pretty marvelous alloys around.
> Cerrosafe melts at a low enough temperature (165F) so that you can, with
> some discomfort, hold a puddle in the palm of your hand. It shrinks upon
> solidifying to facilitate removal from the mold, then expands at room
> temperature to exactly the size of the mold it froze in. Gunsmiths use
> it to gauge size and roundness of cartridge chambers. Ain't technology
> grand?
Are YOU willing to make repairs over 1000 feet in the air, while
hanging from a harness? There are some pretty nasty winds at that
level, so close to the ocean. Some people don't try to get by with half
assed repairs. This is a straight vertical run, other than the
flanges. As I stated earlier, the waveguide was under warranty and the
tower lease included all required repairs. IOW, WE were not allowed to
even attempt a repair, even though the tower was on the TV station's
property.
Grouchy
> Hi:
>
> Clipping in an audio signal results when an audio device receives a
> signal that is too loud. The audio signal distorts into square-waves
> because the "tops" of the signal are flattened. The device cannot
> handle power levels over a certain level. When this level is exceeded,
> clipping occurs. Clipping is usually harsher in digital devices than
> in analog devices. Analog clipping tends to be fuzzy and soft compared
> to digital clipping.
>
> What is the visual-equivalent of "clipping"? Is there a difference
> between analog and digital in terms of visual-clipping? If so, what is
> the difference?
>
> monitors?
>
>
> Radium
Sir,
I suggest you begin here regarding video 'clipping'... it's the NTSC
site and has links to more in depth sites if it doesn't answer your
question:
http://www.ntsc-tv.com/index.html
In a manner of speaking, digital compression methods are all sort of
"clipping" in a certain sense of the term... Maybe you're thinking of
'clamping' circuits, rather than clipping networks?
Best,
Grouchy
Arny Krueger
"Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
news:46E66841...@earthlink.net...
> Are YOU willing to make repairs over 1000 feet in the air, while
> hanging from a harness?
I always liked the time I spent in a climbing harness attached to something
firm. It was the unclipping to take up some new position or the time that
had to be spent high unclipped that bothered me.
I've never worked on towers higher than about 80 feet, but as they say, its
the first 40 feet that kills you. :-(
In fact a tech at another battery in our batallion did fall off a tower
during my tour in Fla. and suffered the expected fate. :-(
The worst thing that ever happened to me was a mild head injury due loosing
my balance and ending up too close to a slewing radar. Towers in Homestead
were covered with about an inch of water due to condensation from the
everglades and the ocean, in the morning. I was approaching the safety
switch at the time!
> There are some pretty nasty winds at that
> level, so close to the ocean. Some people don't try to get by with half
> assed repairs. This is a straight vertical run, other than the
> flanges. As I stated earlier, the waveguide was under warranty and the
> tower lease included all required repairs. IOW, WE were not allowed to
> even attempt a repair, even though the tower was on the TV station's
> property.
The anecdote reveals the context with the mention of X-band. It was likely a
military radar, and the brazing was probably done with the piece of
waveguide removed from the radar and sitting on a bench.
The part about the story that I don't get is that we had ionization
detectors on our waveguides, and they always seemed to shut things down
before the situation got too far out of hand.
dpi...@cartchunk.org
> "Michael A. Terrell" <mike.terr...@earthlink.net> wrote in messagenews:46E66841...@earthlink.net...
>
> Are YOU willing to make repairs over 1000 feet in the air, while
> > hanging from a harness?
>
> the first 40 feet that kills you. :-(
Actually, no, it's the last couple of inches.
I doubt that many people ever died of falling. They
pretty much all died of the sudden stop at the end.
> The worst thing that ever happened to me was a mild
> head injury due loosing my balance and ending up too
> close to a slewing radar.
Suggesting ... ?