Electronics Forums > CRT monitor query: Relationship between video input bandwidth and refresh rate/resolution settings possible...

# CRT monitor query: Relationship between video input bandwidth and refresh rate/resolution settings possible...

Ken Moiarty
Guest
Posts: n/a

 04-14-2006, 08:59 AM
Hi, I'm trying to search the web for 19" to 22" CRT monitors on the market
which provide the *highest refresh rates per a certain range of resolutions
(e.g. starting at 1024 x 768 thru to 1600 x 1200). In other words, I'm
looking for monitor product specs that show a list of resolutions and their
corresponding maximum refresh rates as would be presented in a table. This
is hard to tailor a Google search for.

Therefore for keyword terms, I'm turning my attention to "video input
bandwidth" (rated on the order of hundreds of mHz, rather than the mere tens
of Hz that apply to vertical refresh rates) as a search term/variable to use
in my searching. In my browsing I get the impression that the higher the
value of this "video input bandwidth" parameter, the higher the refresh rate
possible for a given resolution (when all other things being equal, of
course). But I seem unable to find anything to confirm this hunch.

If someone here, who is more knowledgeable than I on this subject, could
please enlighten (and/or correct) me here, or just point me towards a good
faq site on this topic, I'd appreciate it very much. For example, is there
any kind of linear mathematical relationship between a monitor's video input
bandwidth value, and it's refresh rate values relative to various possible
resolutions? Or perhaps you might just tell me what might be the upper
limit or ceiling in terms of the maximum "video input bandwidth" values
realistically obtainable (e.g. 300mHz?, 350mHz?, 900mHz?, what?). Then I
could have some idea of what range of values I might begin punching into my
Google search attempts (as in, 'try this and see what me comes up with',
etc...etc...) .

TIA,

Ken

--------------------------------------------------------------------------------------------

* FYI, for those who just may be curious: Because of local problem of 60 Hz
alternating magnetic-field interference emanating from a major high voltage
powerline corridor running right through part of my back yard, in order to
make good use of a CRT monitor I have to run it at refresh rates that are
multiples of 60 Hz (e.g. 60 Hz, 120 Hz, 180 Hz, etc.).

One might think the preferred alternative might be to just get an LCD
monitor (or if spending gobs of money for ugly aesthetics were somehow not
complicating factor here is however is for my purposes here an LCD monitor
won't do. (I have already invested in an LCD monitor for regular computer
use.) Here I'm looking for a monitor which I can use for viewing very
high-quality high-resolution Stereo 3-D video, and this can only be done
using a large CRT monitor.

Further necessitating the desire to search for a CRT monitor based on the
highest refresh rates available, not only must this monitor refresh at some
multiple of 60 Hz to avoid local electromagnetic interference as I just
mentioned, but because of the demands of high quality stereo 3-D viewing the
vertical refresh rate absolutely cannot be anything less than 120 Hz;
although in fact a somewhat higher refresh rate than 120 Hz (e.g. 135 Hz) is
preferable in order to avoid noticeable flicker during 3-D viewing. (This is
only because, although the monitor is refreshing at 120 Hz, stereo 3-D video
is using two vertical scans to produce one interlaced stereo 3-D frame,
meaning the actual stereo 3-D refresh rate rate is still a mere 60 Hz as far
as each eye is permitted to see (due to the stereo 3D shutter glasses).
This results in flicker just like that experienced with a monitor set to 60
Hz refresh rate for general use.) Therefore given the constraints imposed
by my powerline interference problem, to achieve a monitor refresh rate
above 120 Hz, I would have to leap to the next multiple of 60 Hz, which
would of course be 180 Hz refresh rate. And to achieve this refresh rate in
and of itself, it is not difficult to find a monitor capable of 180 Hz.
What is proving difficult however (for me at least) is finding a monitor
that can refresh at 180 Hz whilst display at 1024 x768 or higher resolution!

And btw, not even this is the end of the story: In addition to the above
requirement, the monitor's horizontal sync frequency must be no less than
126 kHz --ideally 130-140 kHz. Thus I must be sure to avoid any monitor in
which this parameter has been compromised by the manufacturer the interest
of competitive pricing, knowing that many monitor buyers will simply not be
aware in this regard. But this parameter simply is not mentioned or even
referred to in the specs provided for any of the CRT monitor models I've so
http://pymol.sourceforge.net/stereo3d.html , if anyone wants to see the
source of my info pertaining stereo 3-D video.)

Mark M
Guest
Posts: n/a

 04-14-2006, 10:07 AM
"Ken Moiarty" <(E-Mail Removed)> wrote in message news:(E-Mail Removed)...
> Hi, I'm trying to search the web for 19" to 22" CRT monitors on the market
> which provide the *highest refresh rates per a certain range of resolutions
> (e.g. starting at 1024 x 768 thru to 1600 x 1200). In other words, I'm
> looking for monitor product specs that show a list of resolutions and their
> corresponding maximum refresh rates as would be presented in a table. This
> is hard to tailor a Google search for.
>
> Therefore for keyword terms, I'm turning my attention to "video input
> bandwidth" (rated on the order of hundreds of mHz, rather than the mere tens
> of Hz that apply to vertical refresh rates) as a search term/variable to use
> in my searching. In my browsing I get the impression that the higher the
> value of this "video input bandwidth" parameter, the higher the refresh rate
> possible for a given resolution (when all other things being equal, of
> course). But I seem unable to find anything to confirm this hunch.
>
> If someone here, who is more knowledgeable than I on this subject, could
> please enlighten (and/or correct) me here, or just point me towards a good
> faq site on this topic, I'd appreciate it very much. For example, is there
> any kind of linear mathematical relationship between a monitor's video input
> bandwidth value, and it's refresh rate values relative to various possible
> resolutions? Or perhaps you might just tell me what might be the upper
> limit or ceiling in terms of the maximum "video input bandwidth" values
> realistically obtainable (e.g. 300mHz?, 350mHz?, 900mHz?, what?). Then I
> could have some idea of what range of values I might begin punching into my
> Google search attempts (as in, 'try this and see what me comes up with',
> etc...etc...) .
>
> TIA,
>
> Ken
>
>
>
> --------------------------------------------------------------------------------------------
>
>
> * FYI, for those who just may be curious: Because of local problem of 60 Hz
> alternating magnetic-field interference emanating from a major high voltage
> powerline corridor running right through part of my back yard, in order to
> make good use of a CRT monitor I have to run it at refresh rates that are
> multiples of 60 Hz (e.g. 60 Hz, 120 Hz, 180 Hz, etc.).
>
> One might think the preferred alternative might be to just get an LCD
> monitor (or if spending gobs of money for ugly aesthetics were somehow not
> complicating factor here is however is for my purposes here an LCD monitor
> won't do. (I have already invested in an LCD monitor for regular computer
> use.) Here I'm looking for a monitor which I can use for viewing very
> high-quality high-resolution Stereo 3-D video, and this can only be done
> using a large CRT monitor.
>
> Further necessitating the desire to search for a CRT monitor based on the
> highest refresh rates available, not only must this monitor refresh at some
> multiple of 60 Hz to avoid local electromagnetic interference as I just
> mentioned, but because of the demands of high quality stereo 3-D viewing the
> vertical refresh rate absolutely cannot be anything less than 120 Hz;
> although in fact a somewhat higher refresh rate than 120 Hz (e.g. 135 Hz) is
> preferable in order to avoid noticeable flicker during 3-D viewing. (This is
> only because, although the monitor is refreshing at 120 Hz, stereo 3-D video
> is using two vertical scans to produce one interlaced stereo 3-D frame,
> meaning the actual stereo 3-D refresh rate rate is still a mere 60 Hz as far
> as each eye is permitted to see (due to the stereo 3D shutter glasses).
> This results in flicker just like that experienced with a monitor set to 60
> Hz refresh rate for general use.) Therefore given the constraints imposed
> by my powerline interference problem, to achieve a monitor refresh rate
> above 120 Hz, I would have to leap to the next multiple of 60 Hz, which
> would of course be 180 Hz refresh rate. And to achieve this refresh rate in
> and of itself, it is not difficult to find a monitor capable of 180 Hz.
> What is proving difficult however (for me at least) is finding a monitor
> that can refresh at 180 Hz whilst display at 1024 x768 or higher resolution!
>
> And btw, not even this is the end of the story: In addition to the above
> requirement, the monitor's horizontal sync frequency must be no less than
> 126 kHz --ideally 130-140 kHz. Thus I must be sure to avoid any monitor in
> which this parameter has been compromised by the manufacturer the interest
> of competitive pricing, knowing that many monitor buyers will simply not be
> aware in this regard. But this parameter simply is not mentioned or even
> referred to in the specs provided for any of the CRT monitor models I've so
> http://pymol.sourceforge.net/stereo3d.html , if anyone wants to see the
> source of my info pertaining stereo 3-D video.)

Here's a relatively recent link (Jan 2006) that lists CRT models you'll
probably still be able to find:
http://pymol.sourceforge.net/stereo3d.html

pbdelete@spamnuke.ludd.luthdelete.se.invalid
Guest
Posts: n/a

 04-14-2006, 01:09 PM
In sci.electronics.basics Ken Moiarty <(E-Mail Removed)> wrote:
>Hi, I'm trying to search the web for 19" to 22" CRT monitors on the market
>which provide the *highest refresh rates per a certain range of resolutions
>(e.g. starting at 1024 x 768 thru to 1600 x 1200). In other words, I'm
>looking for monitor product specs that show a list of resolutions and their
>corresponding maximum refresh rates as would be presented in a table. This
>is hard to tailor a Google search for.

>Therefore for keyword terms, I'm turning my attention to "video input
>bandwidth" (rated on the order of hundreds of mHz, rather than the mere tens
>of Hz that apply to vertical refresh rates) as a search term/variable to use
>in my searching. In my browsing I get the impression that the higher the
>value of this "video input bandwidth" parameter, the higher the refresh rate
>possible for a given resolution (when all other things being equal, of
>course). But I seem unable to find anything to confirm this hunch.

>If someone here, who is more knowledgeable than I on this subject, could
>please enlighten (and/or correct) me here, or just point me towards a good
>faq site on this topic, I'd appreciate it very much. For example, is there
>any kind of linear mathematical relationship between a monitor's video input
>bandwidth value, and it's refresh rate values relative to various possible
>resolutions? Or perhaps you might just tell me what might be the upper
>limit or ceiling in terms of the maximum "video input bandwidth" values
>realistically obtainable (e.g. 300mHz?, 350mHz?, 900mHz?, what?). Then I

300 mHz = .3 Hz.. watch out with those suffixes.

Anyway:

X_pixels * Y_pixels * Vertical_refresh * Nth_harmonic = Bandwidth
(asfair)

One person mentioned one should have a monitor that manages 3rd harmonic
to get that "crisp" video. While you will get a picture at 1st harmonic

So for a 1600x1200 pixel @ 60 Hz:
1600*1200*60*3 = 345600000 Hz = 345.6 MHz

CWatters
Guest
Posts: n/a

 04-14-2006, 06:41 PM

<(E-Mail Removed)> wrote in message
news:443f9f0f\$0\$491\$(E-Mail Removed)...
> X_pixels * Y_pixels * Vertical_refresh * Nth_harmonic = Bandwidth
> (asfair)
>
> One person mentioned one should have a monitor that manages 3rd harmonic
> to get that "crisp" video. While you will get a picture at 1st harmonic

>
> So for a 1600x1200 pixel @ 60 Hz:
> 1600*1200*60*3 = 345600000 Hz = 345.6 MHz

There should be a a factor of 1/2 in there somewhere because the max
frequency occurs with alternate black and white pixels. Draw the square wave
and you can see the base frequency is half the pixel rate.

Ken
Guest
Posts: n/a

 04-15-2006, 03:34 AM
(E-Mail Removed)lid wrote:
>
> 300 mHz = .3 Hz.. watch out with those suffixes.
>

Whoops.

> Anyway:
>
> X_pixels * Y_pixels * Vertical_refresh * Nth_harmonic = Bandwidth
> (asfair)
>
> One person mentioned one should have a monitor that manages 3rd harmonic
> to get that "crisp" video. While you will get a picture at 1st harmonic

Being an electronics layperson I'm not sure what, "manages 3rd
harmonic", refers to. Would this have something to do with the role of
a "3-comb filter"?

>
> So for a 1600x1200 pixel @ 60 Hz:
> 1600*1200*60*3 = 345600000 Hz = 345.6 MHz

Terrific! Thank you.

Ken

Jasen Betts
Guest
Posts: n/a

 04-15-2006, 07:29 AM
On 2006-04-14, Ken Moiarty <(E-Mail Removed)> wrote:
> Hi, I'm trying to search the web for 19" to 22" CRT monitors on the market
> which provide the *highest refresh rates per a certain range of resolutions
> (e.g. starting at 1024 x 768 thru to 1600 x 1200). In other words, I'm
> looking for monitor product specs that show a list of resolutions and their
> corresponding maximum refresh rates as would be presented in a table. This
> is hard to tailor a Google search for.
>
> Therefore for keyword terms, I'm turning my attention to "video input
> bandwidth" (rated on the order of hundreds of mHz, rather than the mere tens
> of Hz that apply to vertical refresh rates) as a search term/variable to use
> in my searching. In my browsing I get the impression that the higher the
> value of this "video input bandwidth" parameter, the higher the refresh rate
> possible for a given resolution (when all other things being equal, of
> course). But I seem unable to find anything to confirm this hunch.

sounds right to me... basically if your source emits pixels at greater than
twice the bandwidth the display will not respond fast enough to distinguish
individual pixels. that's the "ceiling" thing start blurring out before that
point, somewhere above half the bandwidth the effect begins to become
noticable.

> If someone here, who is more knowledgeable than I on this subject, could
> please enlighten (and/or correct) me here, or just point me towards a good
> faq site on this topic, I'd appreciate it very much.

> For example, is there
> any kind of linear mathematical relationship between a monitor's video input
> bandwidth value, and it's refresh rate values relative to various possible
> resolutions?

no. the scan and video signals don't intterract inside the monitor
(until they both meet at the CRT)

> Or perhaps you might just tell me what might be the upper
> limit or ceiling in terms of the maximum "video input bandwidth" values
> realistically obtainable (e.g. 300mHz?, 350mHz?, 900mHz?, what?).

Define realisitic. tubes could be made with bandwiths in the low gigahertz
without too much trouble. if they aren't already like that.

> * FYI, for those who just may be curious: Because of local problem of 60 Hz
> alternating magnetic-field interference emanating from a major high voltage
> powerline corridor running right through part of my back yard, in order to
> make good use of a CRT monitor I have to run it at refresh rates that are
> multiples of 60 Hz (e.g. 60 Hz, 120 Hz, 180 Hz, etc.).

ah... TVs do that too...

but at 120Hz wouldn't 60Hz interferance deflect alternate scans in the
opposite direction?

> What is proving difficult however (for me at least) is finding a monitor
> that can refresh at 180 Hz whilst display at 1024 x768 or higher resolution!

the video bandwidth is proportional to the maximum number of pixels
times the refresh rate.

> And btw, not even this is the end of the story: In addition to the above
> requirement, the monitor's horizontal sync frequency must be no less than
> 126 kHz --ideally 130-140 kHz.

768*180 = 138240 Hz , if it can do 768 lines at 180 Hz the horizontal rate
will be over 138 kHz, probably over 140kHz.

> Thus I must be sure to avoid any monitor in
> which this parameter has been compromised by the manufacturer the interest
> of competitive pricing, knowing that many monitor buyers will simply not be
> aware in this regard. But this parameter simply is not mentioned or even
> referred to in the specs provided for any of the CRT monitor models I've so
> http://pymol.sourceforge.net/stereo3d.html , if anyone wants to see the
> source of my info pertaining stereo 3-D video.)

you will be able to use the product scanlines * refreshrate to approximate
the horizontal rate (add about 20 to scanlines to account for the vertical
retrace period)

eg: if aa display can do 1200 lines at 120Hz refresh rate it can do
800 lines at 180Hz, and to avchieve either it needs over 144Khz horizontal
rate.

Bye.
Jasen

CWatters
Guest
Posts: n/a

 04-15-2006, 08:31 AM

"Ken" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> (E-Mail Removed)lid wrote:
> Being an electronics layperson I'm not sure what, "manages 3rd
> harmonic", refers to. Would this have something to do with the role of
> a "3-comb filter"?

No. If you want nice sharp edges on your pixels you need to feed tham a
square wave not a sine wave. To make a square wave you need a mixture of
more than one sine wave. To make a square wave with infinitly steep edges
would need to use an infinite number of odd harmonics (multiples of
1,3,5,7,9...) of the base frequency. To make one with reasonably steep edges
you only need a few (perhaps only the third) harmonic.

http://hyperphysics.phy-astr.gsu.edu...dio/geowv.html

Mark M
Guest
Posts: n/a

 04-15-2006, 09:24 AM
"CWatters" <(E-Mail Removed)> wrote in message news:Ub20g.373321\$(E-Mail Removed)-ops.be...
>
> "Ken" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) oups.com...
> > (E-Mail Removed)lid wrote:
> > Being an electronics layperson I'm not sure what, "manages 3rd
> > harmonic", refers to. Would this have something to do with the role of
> > a "3-comb filter"?

>
> No. If you want nice sharp edges on your pixels you need to feed tham a
> square wave not a sine wave. To make a square wave you need a mixture of
> more than one sine wave. To make a square wave with infinitly steep edges
> would need to use an infinite number of odd harmonics (multiples of
> 1,3,5,7,9...) of the base frequency. To make one with reasonably steep edges
> you only need a few (perhaps only the third) harmonic.
>
> http://hyperphysics.phy-astr.gsu.edu...dio/geowv.html

Yes, but there's a practical consideration as well. If you operate
a CRT monitor at or even near its bandwidth limit, image quality
will suffer terribly. Quite a bit of headroom is required to avoid
this issue.

Gene E. Bloch
Guest
Posts: n/a

 04-16-2006, 12:10 AM
On 4/15/2006, CWatters posted this:
> "Ken" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) oups.com...
>> (E-Mail Removed)lid wrote:
>> Being an electronics layperson I'm not sure what, "manages 3rd
>> harmonic", refers to. Would this have something to do with the role of
>> a "3-comb filter"?

>
> No. If you want nice sharp edges on your pixels you need to feed tham a
> square wave not a sine wave. To make a square wave you need a mixture of
> more than one sine wave. To make a square wave with infinitly steep edges
> would need to use an infinite number of odd harmonics (multiples of
> 1,3,5,7,9...) of the base frequency. To make one with reasonably steep edges
> you only need a few (perhaps only the third) harmonic.
>
> http://hyperphysics.phy-astr.gsu.edu...dio/geowv.html

And to clarify for Ken, the self-confessed "electronics layperson", a
periodic wave is composed of a fundamental frequency, which is the
frequency we associate with the wave, and various integer multiples of
that frequency. These are called harmonics or overtones.

The first harmonic is the base frequency. The second harmonic is twice
that frequency, the third three times that, and so on. Other important
factors are the amplitudes and phases of these harmonics, which
determine the exact wave shape.

Computing all the phases and amplitudes will be left as an exercise for

The first overtone is the same as the second harmonic, and so on. The
fundamental would be the zeroth overtone, but it's not conventional to
use that term.

Gino

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

Tom MacIntyre
Guest
Posts: n/a

 04-16-2006, 06:33 PM
On Sat, 15 Apr 2006 17:10:16 -0700, Gene E. Bloch
<(E-Mail Removed)> wrote:

>On 4/15/2006, CWatters posted this:
>> "Ken" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed) oups.com...
>>> (E-Mail Removed)lid wrote:
>>> Being an electronics layperson I'm not sure what, "manages 3rd
>>> harmonic", refers to. Would this have something to do with the role of
>>> a "3-comb filter"?

>>
>> No. If you want nice sharp edges on your pixels you need to feed tham a
>> square wave not a sine wave. To make a square wave you need a mixture of
>> more than one sine wave. To make a square wave with infinitly steep edges
>> would need to use an infinite number of odd harmonics (multiples of
>> 1,3,5,7,9...) of the base frequency. To make one with reasonably steep edges
>> you only need a few (perhaps only the third) harmonic.
>>
>> http://hyperphysics.phy-astr.gsu.edu...dio/geowv.html

>
>And to clarify for Ken, the self-confessed "electronics layperson", a
>periodic wave is composed of a fundamental frequency, which is the
>frequency we associate with the wave, and various integer multiples of
>that frequency. These are called harmonics or overtones.
>
>The first harmonic is the base frequency. The second harmonic is twice
>that frequency, the third three times that, and so on. Other important
>factors are the amplitudes and phases of these harmonics, which
>determine the exact wave shape.

Some would argue that what you refer to as the first harmonic is the
fundamental, with the first harmonic being twice that of the
fundamental.

Tom

>
>Computing all the phases and amplitudes will be left as an exercise for
>
>The first overtone is the same as the second harmonic, and so on. The
>fundamental would be the zeroth overtone, but it's not conventional to
>use that term.
>
>Gino

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