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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions. |
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10th Sep 2021, 12:10 pm | #1 |
Tetrode
Join Date: Aug 2010
Location: Andalusia, Spain
Posts: 74
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UHF TV transmitter. (Micro UHF Analog TV transmitter).
Came across this novel idea which I thought might interest some restorers:
https://www.tomshardware.com/news/ra...uhf-to-crt-tvs |
10th Sep 2021, 2:33 pm | #2 |
Moderator
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Re: UHF transmitter
UHF TV transmitters are very illegal indeed in the UK. They're one of the very few items of transmission hardware that it's actually illegal to possess rather than use. I don't know if Ofcom are still as strict about the rules after analogue switchoff, but I wouldn't go down this road without a very good reason indeed.
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10th Sep 2021, 3:16 pm | #3 |
Tetrode
Join Date: Aug 2010
Location: Andalusia, Spain
Posts: 74
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Re: UHF transmitter
I have heard of the terms legal and illegal but not very illegal.
Aren't UHF modulators (which are transmitters lacking a radiator) used in vintage video recorders and computers? FM and AM transmitters are also illegal but used carefully and range limited to the locality of the receiver, do no harm to the radio environment |
10th Sep 2021, 3:48 pm | #4 |
Heptode
Join Date: Jun 2005
Location: Sunderland, Tyne and Wear, UK.
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Re: UHF transmitter
Here in the UK years ago you could buy a video sender it had 2 phono connectors 1 for video and 1 for audio the audio was pretty poor and it was not very stable it would drift off tune kind regards Bob
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10th Sep 2021, 4:07 pm | #5 | |
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Re: UHF transmitter
Quote:
The reason there are such strict rules about this is there was a political panic over UHF video senders in the early 80s. These weren't a bridge using non broadcast frequencies like modern examples, but simple UHF transmitters that you hooked up to your VCR or satellite box. Both VHS and Sky were just taking off at the time, and imported video senders were selling in large quantities from unregulated outlets such as market stalls. A full blown regulatory panic ensued, with emergency legislation passed in Parliament making it illegal to possess, never mind use, a UHF broadcast transmitter of any power. A vast range of dubious equipment can be owned in the UK - you can own a 500kW SW transmitter if you want to - but you only commit an offence if you use it without a suitable licence. |
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10th Sep 2021, 4:50 pm | #6 | ||
Heptode
Join Date: Jun 2005
Location: Sunderland, Tyne and Wear, UK.
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Re: UHF transmitter
Quote:
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10th Sep 2021, 5:00 pm | #7 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,483
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Re: UHF transmitter
Surely the important point here is the power output level and how it is conveyed to the set. UHF modulators are in effect very low power UHF transmitters, with good reason, they were intended to seem indistiguishable from any other off-air UHF analogue transmission so that they could be tuned in and 'received' by a set originally only designed to receive off-air broadcast signals.
I (and I'm sure many others) once attached something like a set-top Yagi to the output of a modulator on a home computer or game console out of curiosity, just to see how far it would go. As it turned out, quite far, given the gain supplied by a typical Yagi. I would imagine these Pi based units would be quite safe to use if the output was attenuated down to the level typically supplied by an analogue RF modulator and cabled, rather than transmitted, to the UHF input of the receiver in question. Given the potential cost of that TX board plus the Pi and plus any possible extras you might need such as a PSU and SD card, I would tend to solve this problem by using one of the relatively low cost synthesised AV to RF modulators available off the peg - designed for that job, nothing more, nothing less. You can feed one of those from a VCR or DVD player or yes, even the composite video + stereo audio output available on all of the larger Pis. |
10th Sep 2021, 5:49 pm | #8 |
Moderator
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Re: UHF transmitter
This is an open forum, and also one frequented by all sorts of people, with all sorts of involvement in radio regulatory matters. Not at all suitable for discussing forbidden stuff.
I took 'very illegal' to mean the sort of thing which would be assiduously pursued if it came to light. Assault and battery rather than prolonged parking... David
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10th Sep 2021, 7:56 pm | #9 |
Octode
Join Date: Jan 2007
Location: Dorridge, West Midlands, UK.
Posts: 1,475
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Re: UHF transmitter
As far as I can see it is only a low power modulator chip 200mW similar to what we have in Auroras and Hedghogs, used sensibly it should be possible to use legally to modulate the composite output from your Raspberry pi to feed your 625 line TVs etc the thing to avoid is a long unscreened lead. I think the article was written for an international audience where in many places it would be legal, we just have too be a little more careful to comply with UK rules.
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10th Sep 2021, 8:41 pm | #10 |
Heptode
Join Date: Jun 2005
Location: Sunderland, Tyne and Wear, UK.
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Re: UHF transmitter
Hi Chris as Paulsherwin had said in post it is illegal to own a UHF transmitter dont know if a Aurora or Hedghog converters come in to that category if used transmitter as it was designed as a converter not a transmitter Paul will know better than me. But if the signal radiates outside your property thats a different matter could you get a licence from Ofcom to transmit low power 405 VHF for experimental purpose ? kind regards Bob
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10th Sep 2021, 9:27 pm | #11 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: UHF transmitter
If you were a manufacturer you could get a test and development licence for a specific
frequency or band. Some years back a defective Freeview box radiated a signal that lead to a search and rescue op, probably was on the uhf distress beacon channel. There are licence free video links available at 5.8 GHz for drones and these could be used to transmit TV (analogue 405, 625, or whatever) over a limited range. |
10th Sep 2021, 10:02 pm | #12 | |
Heptode
Join Date: Jun 2005
Location: Sunderland, Tyne and Wear, UK.
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Re: UHF transmitter
Quote:
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10th Sep 2021, 10:30 pm | #13 |
Moderator
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Re: UHF transmitter
Wouldn't it have been so much better if an innocuous name like 'Test signal source' had been used rather than transmitter or sender?
David
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11th Sep 2021, 8:18 am | #14 |
Hexode
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
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Re: UHF transmitter
Hello Paul,
In Post #2, you said: << UHF TV transmitters are very illegal indeed in the UK. They're one of the very few items of transmission hardware that it's actually illegal to possess rather than use >> Are you sure about that? Illegal to sell might be closer? I don't know and I would be keen to understand the actual legal position. What about analogue amateur 70cm TV transmitters? I have several in my 'collection', two of which I built from scratch (and used) as G6AOE/T many years ago? Then there's the Marconi drives in the collection from UHF TV transmitters. They are complex units (such as B7400) and are capable in their own right of about 1W output of VSB on frequency. Definitely more than a modulator. Also a Barco UHF VSB drive for 'local' transmission over cable capable of several hundred mW. A transmitter in all but name. Even if is the law to not own them, it's unenforceable. I would have thought that 'illegal to sell' was more likely? Best regards, Paul M |
11th Sep 2021, 9:14 am | #15 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
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Re: UHF transmitter
I don't have the relevant legislation in front of me and am not a lawyer, so I can't quote chapter and verse. The objective was clearly to make it impossible to sell video senders by any means, including privately and at car boot sales. I don't think it was envisaged that the police would be smashing down people's front doors in the dead of night, or raiding genuine museums. Nevertheless, the powers are substantial and did criminalise possession rather than use.
Although the legislation seemed excessive at the time and still does, it was very effective - dodgy imported video senders disappeared from market stalls and independent shops overnight, and have never reappeared. |
11th Sep 2021, 9:33 am | #16 |
Hexode
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
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Re: UHF transmitter
It would be interesting to see the actual legislation and a professional interpretation.
If 'illegal to own', there would have been many exceptions - too many. 'Illegal to sell' is much simpler and the 'to own' interpretation may have come from media reports at the time - their own interpretation which would likely be more sensational. Best regards, Paul M |
11th Sep 2021, 10:38 am | #17 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
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Re: UHF transmitter
It is either Illegal or not, if it is indeed Illegal , than do not even think of using.
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11th Sep 2021, 11:07 am | #18 |
Hexode
Join Date: Nov 2006
Location: Near Lincoln, UK.
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Re: UHF transmitter
Unless the 'to own' legislation was carefully drafted, amateur TV operations on 70 cms would be illegal (they're UHF for sure). Similarly, many large, powerful MATV/CATV installations would likely be illegal too. Neither application is illegal to do - although you need to be a licensed amateur for the former, of course.
I'm very secptical that the law says 'to own' because there's so many potential legitimate uses and users of equipment at least capable of transmission to air. If it is 'to own', it would have to have been a very carefully drafted piece of legislation. Best regards, Paul M |
11th Sep 2021, 11:17 am | #19 |
Moderator
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Re: UHF TV transmitter.
The "proposed" ban gets a mention here:-
https://books.google.co.uk/books?id=...SENDER&f=false This was back in 1988.
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11th Sep 2021, 11:24 am | #20 |
Hexode
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
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Re: UHF TV transmitter.
The law is here:
https://www.legislation.gov.uk/uksi/1998/722/made Specifies 'video sender' - one class of device, I would wager. Best regards, Paul M |