|
Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
|
Thread Tools |
11th Aug 2017, 3:13 am | #1 |
Hexode
Join Date: Jun 2012
Location: Aabenraa, Denmark.
Posts: 262
|
Analogue TV signal with teletext?
I was wondering if there's some kind of way to have multiple signals converted into analogue for TV's to receive as individual channels like back in the analogue days. Is that possible?
|
11th Aug 2017, 9:08 am | #2 |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,814
|
Re: Analog tv signal with teletext?
The only way I can think of would be multiple Freeview boxes, either with built in modulators, or feeding stand-alone modulators, then combine all the outputs into one. There would be no teletext though. If you want to generate some Teletext, it can be done with a raspberry Pi, but would have to be on a separate channel.
Regards, Lloyd |
11th Aug 2017, 10:23 am | #3 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
|
Re: Analogue TV signal with teletext?
Something similar to what you're suggesting was used in hotels/motels back in the analog-TV days: they had a number of sources that were then modulated on to locally generated RF carriers and combined for distribution throughout the building.
This would include a specific "Hotel channel" giving information about services and prices: the other locally-provided content was usually of an adult nature and the modulator for *that* was only turned on late at night.... I've not come across the ability to locally-generate teletext in such a system though: the 'hotel information' pages were a straightforward static-image. Didn't some VCRs also record the teletext part of a PAL stream? If so, you may be able to find some old videotapes and see what was listed on Oracle during a typical 1980s bank-holiday afternoon alongside the inevitable James Bond movie. |
11th Aug 2017, 11:19 am | #4 |
Hexode
Join Date: Jun 2012
Location: Aabenraa, Denmark.
Posts: 262
|
Re: Analogue TV signal with teletext?
How would that 'local' rf generating work in the concept?
|
11th Aug 2017, 11:55 am | #5 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
|
Re: Analogue TV signal with teletext?
The "Hotel channel" systems used a computer whose baseband video output was fed to a 'modulator' - this modulated the computer output and made it appear as a static image on one of the UHF TV channels. BBC Micros and Atari home-computers were often used for this.
https://www.blake-uk.com/uhf-av-modu...n-promod1.html The better ones let you program a number of 'pages' of hotel-information into the computer, which then cycled through them automatically. OK it's not 'teletext' as in the old Oracle/Ceefax we had in the UK, but it was quite satisfactory in a hotel - the people preparing the rooms were told to tune the TVs to channel-1 [the hotel-info channel] and turn the volume down so guests would be presented with the info-channel when they turned the TV on. There's nothing to stop you doing the same today - using a computer to generate pseudo-teletext page content and modulating it on to a UHF carrier so you can have a 'Teletext channel' on your TV. |
11th Aug 2017, 12:28 pm | #6 |
Hexode
Join Date: Sep 2010
Location: Stourbridge, West Midlands, UK.
Posts: 434
|
Re: Analogue TV signal with teletext?
Using multiple freeview boxes will work, but keep the RF outputs well spaced, for example, use channels say, 21, 31, 41, 51, 61 etc for channels instead of say 21, 24, 27, 31, 35 as interference will probably be experienced due to the close proximity of the adjacent channels, the broadcasters managed this OK as they used filters to prevent it.
|
11th Aug 2017, 6:35 pm | #7 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
|
Re: Analogue TV signal with teletext?
SVHS and ordinary Betamax (and I think the Philips recorders, but no personal experience of them) would record enough of the signal to allow substantially error-free Teletext to be viewed. My first VHS recorder, an excellent Mitsubishi B15 single speed model that was really easy to program, would sometimes record teletext, usually with a certain amount of errors, but this depended on the tape used. Some cheap tapes (Comet own brand) would work, whereas some expensive ones (premium TDK) would not, most odd. My understanding is that copyright law prevented manufacturers from drawing attention to the fact that SVHS would record teletext, as that would have been encouraging users to deliberately commit copyright infringement. There was usually an obscure teletext page that stated that teletext pages were protected by copyright and should not be copied. I got my (very deaf) mother a SVHS recorder so that she could use the 888 teletext subtitles when viewing her recordings.
Last edited by emeritus; 11th Aug 2017 at 6:41 pm. |
11th Aug 2017, 11:51 pm | #8 |
No Longer a Member
Join Date: Oct 2015
Location: Middlesex, UK.
Posts: 198
|
Re: Analogue TV signal with teletext?
As others have dealt with how to sort out the pictures/sound, I will stick to the teletext aspect.
As mentioned in a previous post, you can generate teletext with a Raspberry Pi, but it does then end up on it's own channel as it works as a complete raster generator, rather than a VBI inserter. In other words, it has no live video feed through to combine you digital TV box output with analogue teletext. An easy way to do this is to look out for ex broadcast equipment being offered following studio upgrades. In particular, you need to look out for teletext databridges or inserters. These were made by several companies, but I have some by MRG Systems (see attached picture). They rarely fetch more than scrap value when sold on the secondhand market. You can then use one, or more, of these units between your digital set top box's output and a UHF modulator to add a live analogue text service. Of course, you need to produce some content via a PC to send to the inserter, but it is a proper, fully fledged teletext signal that you end up with. With the right inserter you can also produce 888 subtitles. I've previously posted some info on how a news service can be created, and how the kit is set-up, in another thread in a different section. You can find that thread here, more specifically see posts #7 and #8 |
12th Aug 2017, 12:23 am | #9 |
Hexode
Join Date: Oct 2012
Location: London, UK.
Posts: 497
|
Re: Analogue TV signal with teletext?
Teletext is easy. Many European countries still add standard teletext to their digital broadcasts. Get a satellite receiver on one of those channels and put the output into a modulator and on to your TV. Most countries have fastext or flof, Germany uses a different standard called toptext. Most modern TVs will decode either.
|
14th Aug 2017, 1:44 am | #10 |
Hexode
Join Date: Jun 2012
Location: Aabenraa, Denmark.
Posts: 262
|
Re: Analogue TV signal with teletext?
I was thinking on buing a single device called a 'multibox' I've heard those give out a few amount of YV channels that are analog for the TV to decode.
|