magnetic field

[Ant]

On Tue, 12 Aug 2003 12:31:38 GMT, Doug Smith W9WI
<w9wi@invalid.invalid> wrote:

Didn't TBS broadcast a WST text service for quite a while?

Yes. There was another major broadcast group that was pushing WST - I
can't remember who. Setmaker Zenith was also behind it.

This page is rather helpful:

http://teletext.mb21.co.uk/gallery/world/usa/index.shtml

 

[Michael Liebman]

Doug Smith W9WI <w9wi@invalid.invalid> wrote in
news:3F38DE28.7020501@invalid.invalid:

I don't think NABTS stood for
"North American Broadcast Text Service but sure don't recall what it
*did* stand for!

It's EIA-256/ITU-R BT.653, if that helps. Norpak
(http://www.norpak.ca/throo.htm) says it's "North American Basic Teletext
Specification." Video Demystified (http://www.video-demystified.com/,
click glossary) says it's "North American Broadcast Teletext
Specification." Tomato? Tomahto? Big juicy red thing to throw at bad
entertainers?

That's a good point. The most popular stations do relay a national
network roughly half the broadcast day, and would relay the national
teletext service during that period.

One thing to keep in mind, is that most U.S. national networks already
uses a pretty decent sized chunk of the VBI for stuff already. Between
CC, XDS, VITS and Nielsen you are already reducing the datarate of NABTS
by 1/4. Then when you consider that the networks use another 3 or 4 lines
for proprietary data and if you throw in another measurement tool (Sigma
or AMOL), that doesn't leave very much bandwidth for NABTS at all.

When you factor in all of the other interactive type services (Wink,
EPGs, other datacasting, etc.), how is a local broadcaster supposed to
decide what services to provide and where to spend money? How is the
consumer supposed to know how to spend there money on decoding tools?
Fragment the early adopters enough and you'll never reach enough market
penetration to be successful.

Michael

--
Michael Liebman
"I sig, therefore I am."

To reply via email, remove "-DO-REI-ME" from my address.

 

[Jean-Michel Friedt]

I am completely stumped on how to get 10MHZ down to 64 Hurtz using binary
ripple counters I tried to find a 32.768KHZ watch crystal with wire leads
but All I can find is SMC SOIC SOT devices they are so small I can barely
see them

The 10MHZ part I used two pull down 22pF caps tatium film. The resistor I
used on the 4069 out put to the second 22pF cap was 340K The Feedback
(hooked between the in/out of the 4069) resistor I used was 10Meg 1% metal
film.

seems good to me (especially if the whole thing is oscillating).
The point of 32.768 kHz xtal is that it is very easy to divide !
You will find small tin-can shaped fork-resonators on most older
motherboards. They are easy to unsolder and re-use. I have a
drawer full of such salvaged resonators from all kind of borken
appliances, and mostly motherboards, so I'm sure you should manage
to find one as well.

Now concerning you division question, 10.153e6/60=1.6922e+05 so you
feed your 10 MHz output to an 17 bit binary counter and every time
the output reaches 84610=1.6922e+05/2, you toggle the output. Doing
so with discrete components is a bit time consuming and prone to
errors, so I would advise to use a monolithic counter designed for
such purposes (one of the ICM series should do the trick, but I
havent used them for a while so I don't remember which one would suit
your needs -- check for example
http://www.et-info.com/08/types/dt-08-10-icm.htm)

Jean-Michel

 

[Matthew Cook]

Ted Hartson WA8ULG wrote:

3) Some truth here too. Most consumer were only interested in
watching TV. Those who wanted information found bulletin board
services much more powerful. The personal computer provide better
displays than the TV for text and graphics. By the time the Internet
came along, the capacity of Teletext could not compete.

And yet Teletext went ok in France, which had the comprehensive Minitel
system.

 

[The Technical Manager]

Doug Smith W9WI wrote:

The Technical Manager wrote:
1. A law was passed making it a requirement for TV broadcaster to use
some system of captioning and TV manufacturers to incorporate decoding
circuits for captioning before Teletext took off in Europe. The US
closed captioning system predated Teletext and it was a technical
impossibility for a TV channel to incorporate both closed captioning and
Teletext simultaneously. If the broadcaster decided to incorporate
Teletext then all captioning would have to be on a Teletext page and
that would mean owners of an existing closed captioning only TV would
have to buy a Teletext TV if they wanted captions.

The US captioning system is NOT incompatible with teletext. Captioning
uses only line 21; teletext (at least as implemented here) used a
variable number of lines higher in the vertical interval - I want to say
13-18 but it's been a LONG time & my memory is probably wrong.

So it is possible for a broadcaster to transmit both Teletext and closed
captioning simultaneously and for a TV to have decoding circuits for both
Teletext and closed captioning.

The teletext transmission standard is still used for private data
transmission in the U.S.. The Canadian firm Norpak
(http://www.norpak.ca) sells encoding and decoding equipment.

The law requiring caption decoders wasn't enacted until long after
teletext failed as a consumer service. (but again that doesn't matter
as it's possible to caption and run teletext at the same time)

2. The fragmented nature of the broadcasting industry compared to that
of Europe gave little incentive for broadcasters to add Teletext pages
to their channels unless there was a large enough audience with Teletext
TVs. At the same time TV manufacturers were reluctant to add Teletext
decoder circuits to all but their top of the range models because it
would force up consumer prices. A catch 22 situation in other words and
the government did not stick their fingers in to promote Teletext in any
way.

That's probably the biggest reason.

3. Teletext was seen as pointless in the US because of the proliferation
of dial up BBSs that emerged in the 80s prior to the internet. The BBSs
offered a two way communications facility rather than the one way system
of Teletext.

That's probably a significant reason too. Most U.S. telephone
subscribers have unlimited local calling - a single monthly charge
allows making as many calls in the local area as you want, and allows
staying on the line as long as you want. I suspect this made BBSs more
practical here than in Europe.

4. Teletext was developed for 625 line PAL systems and there was no
standard developed for 525 line NTSC systems because of disagreements
between various parties involved. The lack of a standard meant that
broadcasters and TV manufacturers did not know how to proceed if they
wanted to offer Teletext services.

There were two incompatible technical standards for teletext in the USA
at that time. One was similar to that used for 625 PAL, the other
claimed to have several improvements over the European system. (far
better graphics, for one thing.)

Was that the same as the Teletext system used in Japan ?

One American TV manufacturer fitted Teletext decoders in their TVs almost as
standard features. Which system did they support ?

The government made no effort to set a single standard. (Stereo AM/MW
radio was introduced at about the same time - and it's widely believed
the failure of the US government to set a single standard led to the
failure of this innovation too.)

So it was a result of the Reagan administration that liked to keeps its hands
off business and let standards come about from the free market rather than
from government intervention that led to the demise of Teletext as both
systems killed each other.

 

[Doug Smith W9WI]

gmccx wrote:

Although a bit off topic here (OK, way off topic)... I just have to
ask. Are you by any chance originally from Chattanooga? (there was
someone by that name I knew many years ago)

For better or worse there are a LOT of people by this name<grin>.

Nope, I'm originally from Milwaukee.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

 

[Doug Smith W9WI]

The Technical Manager wrote:

So it is possible for a broadcaster to transmit both Teletext and closed
captioning simultaneously and for a TV to have decoding circuits for both
Teletext and closed captioning.

Yes, and in the first case it was commonly done. (actually still is done)

I don't know as a fact that any TVs were ever built that had both
teletext and caption decoders but there's no reason it couldn't be done.

Was that the same as the Teletext system used in Japan ?

I have no idea.

One American TV manufacturer fitted Teletext decoders in their TVs almost as
standard features. Which system did they support ?

That's beyond my memory, but my bet would be it was Zenith in which case
the system would be WST.

So it was a result of the Reagan administration that liked to keeps its hands
off business and let standards come about from the free market rather than
from government intervention that led to the demise of Teletext as both
systems killed each other.

That's probably a fair statement. Though it's probably not fair to tag
the blame on specific parties/individuals, as the Democrats in Congress
didn't really oppose Reagan's plans.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

 

[H. Dziardziel]

On Tue, 12 Aug 2003 19:35:40 -0700, "Howard Henry Schlunder"
<howard_hs@yahoo.com> wrote:

That transformer was not saturating and it is perfectly normal for big
transformers to draw significant current from the mains without any load
attached. The ideal transformer would have an infinite reactance and allow
no current to flow when none is needed. In truth though, they have a large
impedance but still finite. They also have parasitic inductance which means
they will store some energy and have an imperfect power factor.

The reason the transformer got hot was mainly because of core loss and
partially because of resistive loss from the (mostly reactive) 3A on the
primary. Core loss comes about due to magnetic hysterises of a particular
core material and eddy currents and is always present no matter if a load is
attached or not. The core may have been disspating around 80W because of
this reason. Even normal wall bricks will give you an above ambient warm
sensation when touched without a load attached. I believe they dissipate
somewhere around 4W when not in use, so it behoofs you to unplug them if you
don't use them for months at a time. Microwave ovens disconnect the primary
when not in use so they don't waste power unnecessarily.

Howard Henry Schlunder

"Bill Bowden" wrote in message
news:401eed4d.0308121747.5c94b87@posting.google.com...
So, why does a microwave oven power transformer go into
saturation with no load? I tried one awhile back and it
drew over 3 amps from the line with no load. I assume it
was running into saturation since it was getting hot.

-Bill

Adding a bit to that if I may:
Microwave transformers only operate at full load for short
periods. Under full load the core losses are negligible. Nearly
all real power is coupled through the windings' magnetic fields.
And the heating, primarily due to resistive loss, is only short
term.

So, to save money, the transformer primary can be of low
inductance. This also keeps loaded resistive losses low. But,
that causes high unloaded primary current and thus high core loss
along with the unavoidable primary resistive loss.. .

Transformers operating continuously or under varying loads must
have enough primary inductance to keep unloaded current.low enough
to keep core losses acceptable for all load conditions.

 

[Mark Zenier]

In article <3F37BD34.A68B016C@yahoo.co.uk>,
The Technical Manager <techman@yahoo.co.uk> wrote:

What exactly was the real reason why Teletext failed in the US ? I have
had several explanations from the past but is there any truth to them or
are they just rumours ?

1. A law was passed making it a requirement for TV broadcaster to use
some system of captioning and TV manufacturers to incorporate decoding
circuits for captioning before Teletext took off in Europe.

No. Closed captioning, developed by PBS, was early, but the legal
requirement only came after Sears ceased to have the exclusive sales
rights. The FCC mandate started in 1993, I think.

2. The fragmented nature of the broadcasting industry compared to that
of Europe gave little incentive for broadcasters to add Teletext pages
to their channels unless there was a large enough audience with Teletext
TVs. At the same time TV manufacturers were reluctant to add Teletext
decoder circuits to all but their top of the range models because it
would force up consumer prices. A catch 22 situation in other words and
the government did not stick their fingers in to promote Teletext in any
way.

As other posters said, there were two systems, a reformated version
of the PAL system using fixed sized text frames, and the Canadian
system, Telidon (later NABTS), that used variable sized records and had
graphics primitives and needed a microprocessor to decode it. Which
at that time, late 70's, was still some serious bucks.

But there were more reasons.

1. Teletext didn't work with VCRs, which got REALLY BIG during the
critical time frame. The typical consumer VCR only has 1.5 to 2.5 MHz
of video bandwidth and couldn't record it.

2. Cable TV companies got in the way. Some of the big cable companies
claimed that they only agreed to distribute the video and sound and that
they had the right to strip out any network teletext and replace it with
their own data. That meant that about a third of the market could be
cut off.

Besides, the bandwidth sucked. The channel was only about 60 kBps and
all of that was used for page refresh. Remember that it was developed
back in the days before microprocessors and designed to be stupid (no
local mass storage) and low cost. One last use of it that I know of was
some C Band satellite channels where they used all the scan lines, without
any viewable picture.

Mark Zenier mzenier@eskimo.com Washington State resident

 

[Fred Abse]

On Wed, 13 Aug 2003 03:43:40 +0100, Scott Wiper wrote:

64 Hurtz

Yes, it does, doesn't it?



--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Stephen Neal]

On 13/8/03 11:04 am, in article
bhd56t$1058dg$4@ID-182032.news.uni-berlin.de, "Matthew Cook"
<mattax@yahoo.com> wrote:

Ted Hartson WA8ULG wrote:
3) Some truth here too. Most consumer were only interested in
watching TV. Those who wanted information found bulletin board
services much more powerful. The personal computer provide better
displays than the TV for text and graphics. By the time the Internet
came along, the capacity of Teletext could not compete.

And yet Teletext went ok in France, which had the comprehensive Minitel
system

Yep - though there was originally a non-World Systems Text service in use in
France called "Antiope" (Or "TeleAntiope"?) was there not? ISTR that it was
phased out and replaced by VBI WST text relatively recently?

(Was this something to do with the move from Vertical SECAM colour sync
using "bottles" to the horizontal chroma sync more commonly used today?)

Steve

 

[Ivor Jones]

"Mark Zenier" <mzenier@eskimo.com> wrote in message
news:bhggja$7co$1@eskinews.eskimo.com...

[snip]

1. Teletext didn't work with VCRs, which got REALLY BIG during the
critical time frame. The typical consumer VCR only has 1.5 to 2.5 MHz
of video bandwidth and couldn't record it.

I've got a VCR that can record teletext. (Before anyone asks, ex-Radio
Rentals Baird brand, model VC152LX).

Ivor

 

[Ivor Jones]

"Ivor Jones" <this.address@is.invalid> wrote in message
news:bhgl7u$8vl$1@newsg3.svr.pol.co.uk...

"Mark Zenier" <mzenier@eskimo.com> wrote in message
news:bhggja$7co$1@eskinews.eskimo.com...

[snip]

1. Teletext didn't work with VCRs, which got REALLY BIG during the
critical time frame. The typical consumer VCR only has 1.5 to 2.5 MHz
of video bandwidth and couldn't record it.

I've got a VCR that can record teletext. (Before anyone asks, ex-Radio
Rentals Baird brand, model VC152LX).

Ivor

Sorry, I sent the above before I read the post fully, I'm always doing
it..! What I meant to say was my VCR will record subtitling from page 888,
which is probably of more use anyway <grin&gt

Ivor

 

[Ed Ellers]

Doug Smith, W9WI wrote:

"There was another major broadcast group that was pushing WST - I can't
remember who."

Taft Broadcasting, which provided the Keyfax service that common carrier SSS
was piggybacking on the VBI of WTBS. (Turner had nothing to do with it, and
cable viewers around Atlanta couldn't get Keyfax because the cable systems
were taking WTBS off air rather than by satellite.) The same service was
available OTA on Taft's WKRC-TV in Cincinnati, and Zenith offered set-top
WST decoders there on a limited basis before the Digital System 3 chassis
was introduced in 1986; Zenith also sold cable set-tops with WST decoders to
cable operators who wanted to offer Keyfax as a pay service.

 

[Ed Ellers]

Doug Smith, W9WI wrote.

"I don't know as a fact that any TVs were ever built that had both teletext
and caption decoders but there's no reason it couldn't be done."

ITT Semiconductor offered just such a chip to TV makers in time for the 1993
line-21 mandate.

 

[Allan Adler]

Herbert Ross writes:

This how to do it.
http://www.computronics.com.au/kinsten/

It is a nice site. I'd like it better if it also included information
on environmentally responsible ways to dispose of the used chemicals
and maybe also sold stuff to facilitate doing so.

Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Allan Adler]

There is also a free offering by Andreas Weber at
http://www.tech-chat.de/ Follow the AACircuit link.
The site is in German but the "language" is electronics so you'll be
able to follow it. The program itself is available in German- and
English-language versions.

I took a look at the site and I do read German. I didn't see where it
said explicitly what platform(s) the software is intended to run on.

Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[PeterW]

"Ed Ellers" <edellers@mis.net> wrote in
news:R%Y_a.115388$It4.50080@rwcrnsc51.ops.asp.att.net:

Doug Smith, W9WI wrote:

"There was another major broadcast group that was pushing WST - I
can't remember who."

Taft Broadcasting, which provided the Keyfax service that common
carrier SSS was piggybacking on the VBI of WTBS. (Turner had nothing
to do with it, and cable viewers around Atlanta couldn't get Keyfax
because the cable systems were taking WTBS off air rather than by
satellite.) The same service was available OTA on Taft's WKRC-TV in
Cincinnati, and Zenith offered set-top WST decoders there on a limited
basis before the Digital System 3 chassis was introduced in 1986;
Zenith also sold cable set-tops with WST decoders to cable operators
who wanted to offer Keyfax as a pay service.

I Installed this Ceefax-like system in WKRC on PDP 11/24s IIRC. I also
updated the system at one of the Chicago stations. That was back in the
early 1980's. Those were the days.

Peter Whisker
Logica (now LogicaCMG).

 

[PeterW]

[posted and mailed]

PeterW <peterw_no-spam_@freenet.co.uk> wrote in
news:Xns93D8A5B2099D2PeterWpublic@158.234.25.2:

I Installed this Ceefax-like system in WKRC on PDP 11/24s IIRC. I
:also
updated the system at one of the Chicago stations. That was back in
the early 1980's. Those were the days.

Peter Whisker
Logica (now LogicaCMG).

The Chicago station was WFLD btw. I don't think Logica did any other
American systems. The French were trying to get Antiope into the states at
the time with similar poor results I think.

Peter

 

[JeffM]

I took a look at the site and I do read German. I didn't see where it
said explicitly what platform(s) the software is intended to run on.
Allan Adler

The screenshots show it to be a Windows app.