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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 26th Sep 2019, 11:12 pm   #1
Richard_FM
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Default Analogue Teletext Generator

I was wondering what devices are available to generate an analogue teletext pages, as I wanted to make use of the text feature of the Toshiba I recently added to my collection.

After searching online I found a few references to the IMOgen, which sounds great but was only made in limited numbers & sold out quickly.

Is anything else available?
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Old 26th Sep 2019, 11:42 pm   #2
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Default Re: Analogue Teletext Generator

I looked into this for a slightly more specific reason, I had a HDD recorder box which had both analogue and DVB tuners, but since the ending of analogue transmissions its internal clock had no longer kept good time. This was because the unit synchronised its time from the analogue teletext only.

My plan, then, was to put together something which would obtain the real time and date somehow, generate a teletext page with the time and date kept updated, and feed that through a synthesised (therefore rock steady) analogue RF modulator and connect the output from that to the HDD box's analogue tuner input.

The idea was that the HDD box would periodically read the time from the analogue teletext signal just as it originally did from analogue BBC1, probably, and keep itself in sync with the real time.

The ideal platform for this was the Raspberry Pi - it can obtain the current time and date through its network / wifi connection, it has the option of composite video out, and there are a few projects which already do this.

Here's one, found at random

https://www.raspberrypi.org/magpi/teefax/

Having said all that, I never did do any of that. Various other factors forced me to buy a new HDD box instead, and of course that gets its time from DVB, or via its internet connection.
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Old 27th Sep 2019, 3:05 am   #3
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Default Re: Analogue Teletext Generator

I have tried a number of ways to bring back teletext, with some success.

It's possible to receive live teletext from some satellite TV channels. Last time I tried it, Eurosport and RTE (Ireland's national broadcaster) carried teletext. These channels are encrypted but surprisingly the teletext can be received without a subscription or viewing card, using an old non-HD Sky Digibox. RTE doesn't appear in the Sky TV guide and needs to be added manually to the 'Other Channels' menu, unless you have an Irish-registered Sky viewing card.

I posted my results here :

https://www.radios-tv.co.uk/communit.../2/#post-51326


The Raspberry Pi can generate teletext. It was a bit tricky to set up and install the software, especially since I didn't have much experience of Linux, but I got there in the end. See

https://www.radios-tv.co.uk/communit...-raspberry-pi/

Since writing that article, the teastop.co.uk website no longer hosts the files you need. This link still appears to be active: https://github.com/peterkvt80/vbit2/wiki

Also since then, another interesting device has been discovered that regenerates 5 analogue TV channels complete with teletext from a digital terrestrial signal. Called the Multiview T-35 , it was designed to make the digital switchover easier to deal with in hotels, nursing homes etc. where there were large numbers of existing analogue TVs. The Multiview box converts the Freeview EPG into a series of teletext pages, adding them to the analogue signal. More discussion here:

https://www.radios-tv.co.uk/communit...s-lives-again/
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Old 27th Sep 2019, 1:10 pm   #4
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Default Re: Analogue Teletext Generator

Thanks for the replies, I've heard the Raspberry Pi is a useful device for various things but hadn't investigated further.

Hamid, I found your posts on radios-tv & found the link to teastop is dead, but it's nice of you to get an alternative link.

I'll need to look into the Rasberry Pi & Multiview T-35.
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Old 27th Sep 2019, 6:04 pm   #5
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Default Re: Analogue Teletext Generator

Apparently old Betamax Tapes and Some VHS Players can hold teletext information on them- there is information on the web where a small group are trying to re-build old transmitted information, why not try hooking up to the appropriate player and trying some old VHS tapes ? ( Actually I might even have a multi-region VHS player in my Burnley lock up and some off air tapes you can have for free (for the tapes) and a bit of petrol- for the Player as I have to go digging for it !)
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Old 27th Sep 2019, 10:04 pm   #6
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Default Re: Analogue Teletext Generator

VHS tape can indeed hold teletext, but most of the time it is of too poor quality to be directly usable.

There is, however, software that can take this poor quality signal and "fix" it using modern computer hardware. I was successful in doing this with quite a few of my old home-recorded tapes until (a) I ran out of tapes and (b) my VHS machine developed head issues. So I still have everything setup except the player and the tapes!
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Old 27th Sep 2019, 11:21 pm   #7
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Default Re: Analogue Teletext Generator

A few times I've tried to get text of tapes but never seemed to get much if any images.

It looks like the Raspberry Pi method is the easiest & cheapest way to go.

The only Multiview T-35 I could see for sale was way over what I was willing to spend.
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Old 28th Sep 2019, 12:31 am   #8
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Default Re: Analogue Teletext Generator

There is no such thing as analogue teletext. Teletext is and always has been digital, even when added to an analogue TV channel. Itís proper name is world service teletext.
WST is alive and well in much of Europe and can easily be received with a cheap satellite receiver on Astra 1 at 19E. Try German or Italian RAI channels. To be authentic feed to a modulator then your Toshiba.
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Old 30th Sep 2019, 12:38 am   #9
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Default Re: Analogue Teletext Generator

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Originally Posted by winston_1 View Post
There is no such thing as analogue teletext. Teletext is and always has been digital, even when added to an analogue TV channel. It’s proper name is world service teletext.
WST is alive and well in much of Europe and can easily be received with a cheap satellite receiver on Astra 1 at 19E. Try German or Italian RAI channels. To be authentic feed to a modulator then your Toshiba.

You can make an argument that VBI teletext is digital or analogue, it depends on your viewpoint. I seem to remember that the specification defines a "raised cosine" waveform, the front-end of the decoder had a very analogue looking "slicer" to present a more truly digital signal to the decoder proper, and the quality of the VBI pulses was measured by a very analogue technique called "eye-height".

I suppose when people say "analogue text" they simply mean that which was carried on analogue TV as distinct from the MHEG text carried on digital.

The chip-set in old Sky boxes was capable of locally inserting VBI text into the CVBS waveform (not sure if it was present via RGB), but the last time I saw it in operation there was little more than 888 subtitles.
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Old 30th Sep 2019, 12:49 am   #10
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Default Re: Analogue Teletext Generator

Quote:
Originally Posted by rambo1152 View Post

I suppose when people say "analogue text" they simply mean that which was carried on analogue TV as distinct from the MHEG text carried on digital.
Of course that's what we mean, Teletext as broadcast on the analogue channels as distinct from anything Teletext-like broadcast on digital terrestrial channels, etc.
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Old 30th Sep 2019, 2:07 am   #11
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Default Re: Analogue Teletext Generator

Quote:
Of course that's what we mean, Teletext as broadcast on the analogue channels as distinct from anything Teletext-like broadcast on digital terrestrial channels, etc.
Exactly the same teletext that was broadcast on analogue channels in the UK is still broadcast on digital channels in Europe. Still want to call it analogue text?

The UK and later Ireland are the only European countries to use the (inferior and clumsy in my opinion) MHEG text. In the UK only the BBC still use and they have stated they will stop next year.
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Old 30th Sep 2019, 9:06 am   #12
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Default Re: Analogue Teletext Generator

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Originally Posted by rambo1152 View Post
I suppose when people say "analogue text" they simply mean that which was carried on analogue TV as distinct from the MHEG text carried on digital.
Indeed. I don't think this needs to be discussed further.
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