cw@vaxwaller.UUCP (Carl Weidling) (01/25/85)
I'm thinking about getting a high-resolution color monitor that I can also use to watch TV (I have a video tuner and can run the sound part through my stereo). Sooner or later I'm going to break down and get some kind of home computer but I'm still pretty ignorant about what's out there. I assume that a high resolution color monitor can provide an 80 column by 24 line display, and therefore has a higher bandwidth than normal TV's, but are they "downwards compatible"? I happened to pick up the December '84 BYTE and read in the Chaos Manor column "the TI has the only color display (under $10,000 anyway) I know of that you could use day after day for word processing. All the other color systems are too fuzzy and will give you (or at least me) eyestrain after a few hours..." Is this a factor of the video board or the monitor itself? I'm posting this to two newsgroups, if people mail me replies I'll post a summary and hopefully not clog the net with a lot of redundant info. Thanks in advance, Carl Weidling
dsi@unccvax.UUCP (Dataspan Inc) (01/31/85)
Your problem will be in demodulating the NTSC composite colour video
signal if you want to derive any benefits. To get 80 * 24 characters on a
colour screen, the amplifiers driving the picture tube would have to do
13 mHz (approx). On the other hand, I doubt seriously if your TV tuner
is capable of providing any useable response at 4.2 mHz (due to the crudity
of sound traps used in such things) and only mediocre response at 3.58 mHz.
High resolution colour monitors, when operated in the computer graphic
mode, are almost always RGB. That is, there is a separate amplification
channel for red, green, and blue primaries. The output of your tuner is
probably not RGB but composite NTSC video which encodes the colour by
varying the amplitude and phase of a multiplexed subcarrier. You would
then require a demodulator, which are available but are rather expensive,
to convert NTSC to RGB signals.
If you were to do I/Q axis demodulation with the full bandwidth, you
would notice that NTSC really can produce beautiful colour pictures. The
fact that most "consumer" TV sets hack 66 percent of the I-channel bandwidth
(to save money) from 1.5 mc to 500 kc should disturb most people.
You are definitely on the right track, though. Assuming you could
get a "switchable" RGB-NTSC high res monitor, one benefit would be the
smaller dot pitch on the face of the CRT. Having smaller triads of dots
means better high frequency colour detail; virtually every consumer set
does not have enough dots even in the 19 inch size to prevent aliasing
at 4.2 mHz (the upper limit of NTSC). Even with "narrowband" NTSC decoding
(I have a professional monitor that is switchable, with fine pitch CRT)
the fine pitch CRT makes one whale of a difference.
I have long felt that video is very low-fi (well, a Conrac 5700 pro
monitor and Tektronix demodulator makes me rather biased...) and that
real high performance VIDEO COMPONENTS are required. These are NOT the
kinds of crap you see as good stuff in Video or Sterno Review. The tuners
used in a Zenith Z-TAC cable box are atrocious, mangling all the high
frequencies in both amplitude and phase. I CAN'T STAND DIFFERENTIAL
DISTORTION in a colour picture. You are SUPPOSED to be able to see what
colour shirts people are wearing in the stands while the camera is
set up to capture a basketball tip-off. Broadcasters go to great lengths
to transmit a distortion free image.
We won't even discuss colour under VCR's here. GAKKKKKKKKKKKKKKK!!!
By the time your RF (which comes down the cable or antenna in
reasonable shape) hits the 1) tuner in your cable box (sometimes) and
2) a modulator in your cable box (sometimes) and 3) the tuner in your
VCR and 4) the modulator in your VCR and 5) the tuner in your TV set
the video is ROTTEN, ROTTEN, ROTTEN, ROTTEN, and ROTTEN.
I have deviated somewhat. The point is, while there may be som
improvement, the high res monitor will suffer due to all the manglement
prior to the screen. It's as if you connected a pair of JBL 4311 studio
monitors to the amplifier in a Close-N-Play, thence to a pocket AM radio,
thence to your local AM station, with a compact disc player providing
the program material.
Now, is there interest in a product which would recover 100 % of
the colour signal ( to 4.2 mc) with both composite and RGB outputs? A
real tuner? (Seriously??) Send me some mail -- how much would you spend
to get all 5 packets of the Multiburst signal ruler flat ?
David Anthony
Senior Analog Engineer
DataSpan Corporationcw@vaxwaller.UUCP (Carl Weidling) (02/06/85)
__
A while back I posted a question about using Hi-res monitors
as TV sets if one already had a video tuner. I'd like to thank everyone
who responded and here is a summary of the answers that came back:
----------------------
to my knowledge, almost all commercially available tuners do not have a
high enough bandwidth to deliver the resolution in the monitor. you
may be able to get one of the 'high definition' units in the near
future which makes all of this redundant. in addition, the broadcast
system itself (NTSC) has an upper limit which the highest quality home
units usually reach. until high definition TV broadcasts become
available, i think that you may have a much better unit, but will
deliver almost identically the same picture because of broadcast
limitations. this has been true of FM tuners for quite a while.
of course, your computer games will look fantastic.
Herb Chong...
UUCP: {decvax|utzoo|ihnp4|allegra|clyde}!watmath!water!watdcsu!herbie
CSNET: herbie%watdcsu@waterloo.csnet
ARPA: herbie%watdcsu%waterloo.csnet@csnet-relay.arpa
NETNORTH, BITNET, EARN: herbie@watdcs, herbie@watdcsu
--------------------------
From: Victor Frank <ihnp4!ucbvax!FRANK@CRVAX.ARPA>
[]
Yes, the bandwidth of a VDT is much greater than a home TV. They are down
wards compatible. That is, if you get a wideband color display you can use
it for TV provided you have the proper drivers/interface. There are special
TV tuners for this purpose that put out RGB (red-green-blue) output instead
of the composite video used on the cheaper monitors.
It is a matter of opinion whether a high-res color display is too fuzzy. I
can read my medium-res display (probably around 12 MHz bandwidth), but am not
comfortable with it. The Polo color monitor is available locally for under
$400. It is high res--with one color (usually green) it is quite satisfactory
in my opinion for reading text (80 col x 24 lines).
You should, of course, try to view the display before plunking down your
money; or buy two, green 22 MHz monitors are under $100, one monochrome and
one color.
-----------------------
A lot of the bad quality of color displays is indeed the monitor.
Really good color monitors are **EXPENSIVE**.
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henry
-------------------------
I'm using a TV/Monitor that you can get from the Sears catalog. It costs around
$360, but you get a 13" (?) Color TV and it has RGB and COmposite video
inputs. It works just fine for 80x25 text and you can watch TV while your
compiling programs!
It also has a Green display switch in case your software uses colors you
don't like. And it has a Screen compression button to compress
characters vertically -- I like that mode best.
Problems:
The tuner lets you preset 12 channels, so it's not cable ready
completely. Also, the color adjustment is under a little door on the side of the TV,
and the automatic color adjustment is rigged to disbale itself when you
open the door. This makes it hard to adjust the color -- you gotta do
it by trial and error (or binary search).
I use it with an IBM PC. Works just fine for me.
Gunnar P. Seaburg
Engineering Psychology Research Lab
University of Illinois at Urbana-Champaign
...{ihnp4,pur-ee}!uiucdcs!seaburg
(217) 333-7116
--------------------------------------
Zenith makes a very nice color monitor that can be used with the IBM PC or
clones, as well as any RPG source, or with an NTSC (i.e. TV) source. The
resolution is in exces of 640 horiz x 250 vert, and can be used in interlace
mode if you don't mind some flicker in order to get over 500 lines horiz.
It has a built in speaker and small amplifier. The really nice thing about it
is that it has a switch that turns off the red and blue guns so that you have
a monochromatic green screen for word processing use. It is also available
from Heathkit dealers. The number is something like ZVM-135. Lower
resolution monitors are also available, as well as one high-resolution color
monitor with a long-persistence phosphor so interlaced mode doesn't flicker at
all (this one doesn't work from a TV, I suspect).
Dan T. McGillicuddy
Mitre Corp. - no connection with Zenith or Heath - just like the monitor!
-----------------------------------------
From: amd!nbires!hao!ben (Ben Domenico)
I've been using the Sears Proformance monitor/tv which has inputs for
75ohm, 300ohm antennas, video, audio and rgb. It works fine as a monitor
for the IBM pc color graphics adapter within the limits of that adapter.
It does handle 80 by 25 characters, but it's not up to the standards of
the monochrome because of the inherent limitations in the color adapter.
IBM has now come out with an Enhanced adapter, but the Sears won't be
able to take advantage of the increased resolution of that adapter.
----------------------------------------------
I have a Zenith RGB monitor which I use with a PC-AT. I ones
hooked it to the video output jack of my VCR, and the picture looked
great. If you can get a composite signal from your tuner, I don't see
why it wouldn't work. The resolution of a monitor is infinitely better
than that of a TV. (Incidentally, the Zenith, their top of the line, I
think, has a built-in speaker & amp.) I wonder how Star Trek would
look on a green-screen, though...
ARPA: BRAIL@RU-BLUE.ARPA
UUCP: ...sunrise!allegra!ru-blue!brail
----------------------------
Yes, a high-resolution monitor can be used as a TV just fine - in fact there
is at least one outfit (name escapes me...) that sells a monitor and a TV
tuner separately. Their advertising pitch is that their monitor is smarter
than the average monitor: it's smart enough to be a TV, too. A TV requires
o bandwidth of 6 MHz; an 80-column display needs more like 15 MHz. A monitor
with insufficient bandwidth will produce a fuzzy picture, to the extent of
its being totally unreadable if the bandwidth is too narrow. It's just like
stereo sound - the better the bandwidth of the set, the clearer the sound.
For all-day word processing, it's a good idea to have a monitor with at least
18 MHz bandwidth, and then I'd still avoid a cheap one. Personally, I prefer
monochrome for text applications - there's ALWAYS some fuzz with a colour
monitor - it's inherent in the way the colour image is produced by blending
the effects of the red, blue, and green sub-pixels to produce a white (or
other colour) pixel.
Hope this helps.
Cheers,
Dick Binder (The Stainless Steel Rat)
-----------------------------------------
From: ihnp4!houxm!houxa!jhs
The high resolution (higher bandwidth) causes no downwards
compatability problems but many (most?) of the hi-res color
monitors need a RGB rather than a composite input and the
video output from your VCR (or elsewhere) is composite.
---------------------------------------------
Your problem will be in demodulating the NTSC composite colour video
signal if you want to derive any benefits. To get 80 * 24 characters on a
colour screen, the amplifiers driving the picture tube would have to do
13 mHz (approx). On the other hand, I doubt seriously if your TV tuner
is capable of providing any useable response at 4.2 mHz (due to the crudity
of sound traps used in such things) and only mediocre response at 3.58 mHz.
High resolution colour monitors, when operated in the computer graphic
mode, are almost always RGB. That is, there is a separate amplification
channel for red, green, and blue primaries. The output of your tuner is
probably not RGB but composite NTSC video which encodes the colour by
varying the amplitude and phase of a multiplexed subcarrier. You would
then require a demodulator, which are available but are rather expensive,
to convert NTSC to RGB signals.
If you were to do I/Q axis demodulation with the full bandwidth, you
would notice that NTSC really can produce beautiful colour pictures. The
fact that most "consumer" TV sets hack 66 percent of the I-channel bandwidth
(to save money) from 1.5 mc to 500 kc should disturb most people.
You are definitely on the right track, though. Assuming you could
get a "switchable" RGB-NTSC high res monitor, one benefit would be the
smaller dot pitch on the face of the CRT. Having smaller triads of dots
means better high frequency colour detail; virtually every consumer set
does not have enough dots even in the 19 inch size to prevent aliasing
at 4.2 mHz (the upper limit of NTSC). Even with "narrowband" NTSC decoding
(I have a professional monitor that is switchable, with fine pitch CRT)
the fine pitch CRT makes one whale of a difference.
I have long felt that video is very low-fi (well, a Conrac 5700 pro
monitor and Tektronix demodulator makes me rather biased...) and that
real high performance VIDEO COMPONENTS are required. These are NOT the
kinds of crap you see as good stuff in Video or Sterno Review. The tuners
used in a Zenith Z-TAC cable box are atrocious, mangling all the high
frequencies in both amplitude and phase. I CAN'T STAND DIFFERENTIAL
DISTORTION in a colour picture. You are SUPPOSED to be able to see what
colour shirts people are wearing in the stands while the camera is
set up to capture a basketball tip-off. Broadcasters go to great lengths
to transmit a distortion free image.
We won't even discuss colour under VCR's here. GAKKKKKKKKKKKKKKK!!!
By the time your RF (which comes down the cable or antenna in
reasonable shape) hits the 1) tuner in your cable box (sometimes) and
2) a modulator in your cable box (sometimes) and 3) the tuner in your
VCR and 4) the modulator in your VCR and 5) the tuner in your TV set
the video is ROTTEN, ROTTEN, ROTTEN, ROTTEN, and ROTTEN.
I have deviated somewhat. The point is, while there may be som
improvement, the high res monitor will suffer due to all the manglement
prior to the screen. It's as if you connected a pair of JBL 4311 studio
monitors to the amplifier in a Close-N-Play, thence to a pocket AM radio,
thence to your local AM station, with a compact disc player providing
the program material.
Now, is there interest in a product which would recover 100 % of
the colour signal ( to 4.2 mc) with both composite and RGB outputs? A
real tuner? (Seriously??) Send me some mail -- how much would you spend
to get all 5 packets of the Multiburst signal ruler flat ?
David Anthony
Senior Analog Engineer
DataSpan Corporationlef@nlm-vax.ARPA (Larry Fitzpatrick) (02/07/85)
Although I missed the beginning of this discussion, there are some points raised in this article which are of interest to me. I have been considering getting a monitor (without tuner) as a TV set and using the tuner to a VCR (other?). The implications are not all that clear to me. In article <unccvax.128> dsi@unccvax.UUCP (Dataspan Inc) writes: > > If you were to do I/Q axis demodulation with the full bandwidth, you >would notice that NTSC really can produce beautiful colour pictures. The >fact that most "consumer" TV sets hack 66 percent of the I-channel bandwidth >(to save money) from 1.5 mc to 500 kc should disturb most people. > What does this mean ? What is the I/Q axis ? What is the I-channel? and what units are `mc's ? > You are definitely on the right track, though. Assuming you could >get a "switchable" RGB-NTSC high res monitor, one benefit would be the... I recently saw a NEC hi-res monitor (don't remember the model), sans tuner, with RGB, NTSC and VTR(?) inputs for $425. After watching some local TV on that for a while, I was very disappointed in the picture on the high-dollar Mitsubishi TV's. I don't know what they were using for a TV tuner. Would one get as good a picture using a VCR tuner to supply the input ? (The next pt in this referenced article seems to hint "no"). > We won't even discuss colour under VCR's here. GAKKKKKKKKKKKKKKK!!! Could you please ? > ..., the high res monitor will suffer due to all the manglement >prior to the screen. It's as if you connected a pair of JBL 4311 studio >monitors to the amplifier in a Close-N-Play, thence to a pocket AM radio, >thence to your local AM station, with a compact disc player providing >the program material. > Is it really this bad ? How much does a fine TV/tuner amplifier cost ? I would appreciate any help here. -fitz lef@nlm-vax