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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 8th Oct 2008, 2:10 am   #1
Kat Manton
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Default Providing signals for American TV sets

Hi,

As I've recently acquired three American TV sets, I needed to find a way of providing them with a signal.

A quick search of the 'net came up with a solution in the form of this STEREN Electronics 203-101 RF Modulator. They seem to be readily available from a number of suppliers for under $10; even with shipping to the UK, mine came to around £15 in total.

It's compact, has a built-in PSU (110V AC, naturally) and has stereo audio, composite video and S-Video inputs, with an aerial input and RF output on F connectors.

The last picture shows my Zenith portable set displaying the BBC News 24 Freeview channel, off-air, courtesy of my MythTV system's S-Video output.

I also connected the modulator to my Apple PowerBook's S-Video and audio outputs, configured the second display for 525-line 60Hz, and could watch video files and DVDs fullscreen on the TV using VLC for playback.

I'd expect that a PC running Windows and fitted with a graphics card with a TV output should also be configurable for 525-line. As it's a current standard (not for much longer, though) it's likely that other equipment (some DVD players, perhaps) may have an option for 525-line; it's a little easier than obtaining 405-line or 819-line

(I should also mention that to provide 110V AC to power the modulator and TV set a stepdown transformer is required. I have several, and with the growing number of bits of American equipment here also acquired a 6-way American power strip.)

So, provided you already have a step-down transformer and a source of a 525-line signal, this modulator provides a cheap and easy way to use an American set in the UK.

...Now I just need to get the other two sets working...

Cheers, Kat
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Old 8th Oct 2008, 8:22 am   #2
KeithsTV
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Default Re: Providing signals for American TV sets

Just a quick thought

Many digital cameras with video outputs can be switched between PAL and NTSC. These may provide a relatively cheap source of US signals.

Keith
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Old 8th Oct 2008, 8:57 am   #3
Patrick Dixon
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Default Re: Providing signals for American TV sets

I used to use VHS recorders with US sourced (NTSC) pre-recorded material. I don't know about the modulation though - is it the same in the US and UK?
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Old 8th Oct 2008, 9:35 am   #4
arjoll
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Default Re: Providing signals for American TV sets

Quote:
Originally Posted by Kat Manton View Post
I'd expect that a PC running Windows and fitted with a graphics card with a TV output should also be configurable for 525-line.
This shouldn't be a problem at all - all the ATI PCIE graphics cards I've tried in my Media Centre have had a jumper for PAL/NTSC that changes the output on S-Video or composite. (Unfortunately it doesn't change component video - that's always 525 line 60 Hz so nothing's quite as sharp as 'live' when watching through MCE).
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Old 8th Oct 2008, 4:18 pm   #5
Kat Manton
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Default Re: Providing signals for American TV sets

Quote:
Originally Posted by Patrick Dixon View Post
I don't know about the modulation though - is it the same in the US and UK?
No; otherwise I wouldn't have needed to buy an American modulator...

Both systems use negative vision modulation and FM sound, so they have something in common.

But, the sound/vision carrier spacing is 6 MHz for UK, 4.5 MHz for US.

Also, UK FM sound deviation is ±50kHz with 50µs pre-emphasis, while the US system is ±25kHz and 75µs respectively.

In other words, if you try to tune an American set into a British signal you get either a picture or poor sound, but not both at the same time.

While it's not particularly relevant to vintage sets, the US system uses Zweiton stereo (which means a low-cost modulator like the above can provide stereo audio; it's a relatively 'easy' analogue system) whereas the UK uses NICAM (a digital system which would need more circuitry.)

The CCIR Transmission Systems section of Alan Pemberton's site has full details. The UK uses CCIR System I, the US uses CCIR System M.

I should also have mentioned that the modulator's output is on VHF channel 3 or 4, so it would be usable with earlier American sets which lack a UHF tuner. (While we're comparing systems, UK modulators typically operate around channel 36 UHF.)

Cheers, Kat
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Old 8th Oct 2008, 6:56 pm   #6
Patrick Dixon
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Default Re: Providing signals for American TV sets

OK - I was only ever interested in the picture anyway, and I had no need to bother with RF!
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Old 8th Oct 2008, 7:28 pm   #7
Kat Manton
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Default Re: Providing signals for American TV sets

Hi,

It's a fair point, though

Finding something to view US-standard recordings on isn't usually much of a problem. Many 'non-vintage' TV sets and monitors sold in the UK will lock to the signal (fed in via composite input) and display a picture. Some are also capable of decoding NTSC colour; some may also accept 525-line, 60Hz RGB via SCART.

I'm solving a different problem; I have two seventies sets and one sixties set, all designed purely for off-air reception of System M on VHF and UHF. None have anything other than aerial inputs nor were intended for any other TV standard; so I needed to provide a compatible signal.

Cheers, Kat
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Old 8th Oct 2008, 10:38 pm   #8
chipp1968
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Default Re: Providing signals for American TV sets

is the 60s set working ?
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Old 10th Oct 2008, 9:30 am   #9
Mullard
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Default Re: Providing signals for American TV sets

For monochrome sets I have found that most US sets will frame lock on 50 Hz by adjusting the frame frequency and will line lock as the US line frequency is almost the same as the UK (60 x 525/2 = 15,750, 50 x 625/2 = 15,625). The problem is the sound which uses a 4.5 MHz carrier in the US and 6.00 MHz in the UK. I have retuned a couple of sets and they work OK. I haven't needed to bother to open up the video IF as sets pre-ICs seem to not be that fussy. I have done this as I collect portable TVs with CRTs, and dragging a US modulator and a UK receiver around defeats the point of a portable. I do have a US modulator and this works well.

No use for colour though.

You might like to look at a previous thread:
https://www.vintage-radio.net/forum/...ight=modulator

John
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Old 10th Oct 2008, 6:11 pm   #10
Kat Manton
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Default Re: Providing signals for American TV sets

Hi John,

I remember reading your thread and I'm aware that American sets could be fairly easily adjusted (maybe with slight modification) to receive UK broadcasts.

This thread's about providing signals for unmodified sets, not modifying sets for existing signals.

I collect sets which were designed for standards which are obsolete and/or were never used in the UK. For me, altering any of these sets to receive current UK broadcasts would defeat the point of having them.

For me, part of the fun is devising methods for generating different TV standards, so the sets can be operated without alteration.

It also means the various standard can be compared. I hadn't realised how obvious a 50Hz field rate was until I'd spent a week of evenings watching NTSC-M then switched back to PAL-I..!

Producing many standards with the Linux/MythTV PVR system has proven to be fairly straightforward. It takes me a few seconds to switch the TV system to match the set (when it's a system I've already worked out.)

Once I've generated a particular TV standard and have acquired an appropriate modulator, that's it. Any further sets which I acquire then need only the usual repair/restoration.

It just seems like less effort and a better long-term solution. I'd prefer to arrange generation of a particular standard just the once rather than adapt each and every set I acquire for a signal which isn't going to be around much longer anyway...

Quote:
Originally Posted by Mullard View Post
I have done this as I collect portable TVs with CRTs, and dragging a US modulator and a UK receiver around defeats the point of a portable.
I've considered this too. I'll probably obtain an American 'video sender' to try out at some point. Thus the portability of portable sets is preserved (and I get to choose from 30-odd channels, DVDs and a load of recordings.)

Cheers, Kat
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