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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 7th May 2016, 1:39 pm   #1
deadvideo
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Default RF modulators region specific??

Hi. Complete newbie to forum and subject.

I bought a Radio Shack RF modulator from the US (Channels 3 or 4 operation) and would like to use it on a National TR-809F portable television (which has UHF / VHF connections) here in Japan. I can't seem to get anything on the screen when hooked up to a VHS or DVD player. Do I need to buy a RF modulator specifically for use in Japan or should the Radio Shack one be sufficient? Any info appreciated.
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Old 7th May 2016, 2:42 pm   #2
kan_turk
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Default Re: RF modulators region specific??

Hi
TV RF modulators are indeed region specific - the frequencies used by US channels 3 & 4 were not used for TV in Japan hence your lack of luck - it is sometimes possible to alter frequency range of modulators but this depends on the devices used and your familiarity with RF circuitry
It is also possible to operate on a harmonic of the marked channel but this is a matter for trial & error - you could try tuning the TV to higher freq channels (Jap ch 4 - 12) - sorry for not being more specific as I am not familiar with the actual kit you are using - hope this helps
Rgds
John
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Old 7th May 2016, 3:13 pm   #3
Jim_746
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Default Re: RF modulators region specific??

Hello,

Welcome to the forum.

John is indeed right about RF modulators being region specific.

This Wikipedia article may be of interest to you (https://en.wikipedia.org/wiki/Televi...el_frequencies). There is a graphic at the top of the article that shows the frequency allocations for channels in different countries. Plenty of tables too.

Regards,

Jim
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Old 7th May 2016, 10:27 pm   #4
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Default Re: RF modulators region specific??

A US UHF modulator should do the trick. Modulators designed for Europe/UK/Australia/China/Russia etc will have the wrong sound to vision spacing even though they may cover the correct frquencies. Japan however used the same TV system as the USA just on different frequencies, particularly in the VHF range; in the UHF part of the spectrum the US and Japanese allocations overlap.
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Old 8th May 2016, 1:34 am   #5
emeritus
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Default Re: RF modulators region specific??

In the UK, when camcorders were first introduced, many TVs did not have any AV inputs, and VHS-C camcorders often came with an RF modulator. Modulators were also available as accessories. You may be able to find one in Japan that would do the job.

JVC models came with a special 8 pin plug to fit their camcorders, and you would have to remove it and fit suitable connectors instead. The JVC modulator I have does not tune over the entire UK UHF range.
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Old 9th May 2016, 11:58 am   #6
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Default Re: RF modulators region specific??

I got a Radio Shack modulator for channels A3/A4, from the US many years ago ( I think it had been intended for use with a home computer). I noticed inside that there was a lot of RF filtering being do with coils and capacitors that were covered in sealant - so it would not have been easy to retune. I presume the filtering was to meet FCC regulations.

Unless you build a frequency shifter (VHF to UHF. Labgear sold some in the UK in the early days of UHF TV, for people who were on 625 line VHF TV cable systems but had a UHF only TV) then getting a Japanese modulator may be your best route.

Last edited by SteveCG; 9th May 2016 at 12:01 pm. Reason: extra information
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Old 9th May 2016, 4:15 pm   #7
Mike. Watterson
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Default Re: RF modulators region specific??

Quote:
Originally Posted by SteveCG View Post
Labgear sold some in the UK in the early days of UHF TV, for people who were on 625 line VHF TV cable systems but had a UHF only TV
Still was selling well in to 1980s as some TV TX in West & Midwest were VHF only 625 from 1962 or 1963 (later TV3 & TG4 was UHF, but RTE1 & RTE2 was VHF till 2012 analogue switch off).
UK CTVs and VHS imported to Ireland with UHF only was common.
All the cable networks had channels on Band I till Broadband came in.
They also used Band III and later 275Mhz to 470 MHz (Hyperband? Cable band) on MMDS and Cable. That was only an issue for un-encrypted analogue channels as the Setbox* did mostly did UHF and later SCART
So Labgear converters were common.

[*Chorus for many years till digital and UPC take over used nasty modified USA Jarrold analogue cable boxes, I think they needed a VHF tuner.]

Last edited by Mike. Watterson; 9th May 2016 at 4:25 pm.
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Old 16th Jun 2016, 2:28 pm   #8
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Default Re: RF modulators region specific??

I am a new member so bear with me..

USA channels 3/4 correspond to Vision Carrier M (3) 61.25 Audio 65.75 and (4) 67.25/71.75 ie Band I. Japanese UHF channels start at 171.25 (ie Band III), which as was stated by Kan_turk would be why it doesn't work.

There are modulators out there that can cope with all of the various analogue TV standards. I just bought a Maximum MT47 from a UK electronics dealer on the web in the UK. They also do the MT57 which can modulate A2 Zweiton stereo, which many new UK TV's can decode.

It can be readily programmed for B/G (W Europe), D/K (E Europe), Australia (B), I (UK, Eire, S Africa, HK), L (France), M & N. On this particular devices if you program it for M it outputs Japanese VHF/UHF frequencies and N North American frequencies VHF/UHF.

B/G/D/K/I/L it sets the VHF frequencies to legacy frequencies in Europe for that region and all of the standard European UHF 8Mhz frequencies. Australia is 7mhz UHF/VHF.

It cost about £31 which I didn't think was too bad.

As I get older I am very nostalgic of the old TV's available when I was younger and have always been interested in the multitude of analogue TV standards. I have bought a few working (small) TV's to start a collection, including an old US Sony TV-720U. The modulator will allow me to use them. You can of course get cheap PAL to NTSC converters in the usual places now. I now bitterly regret not having the technical knowledge to understand electronics and how these things work!

Anyway, I hope someone is interested in this!

Cheers


Patrick
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Old 17th Jun 2016, 11:22 am   #9
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Default Re: RF modulators region specific??

Patrick,

Are you aware that the French System L standard is only for VHF on Band III and UHF?

Band I transmissions in France used the L' standard (where the sound carrier is below the vision carrier in frequency).
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Old 19th Jun 2016, 11:13 am   #10
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Default Re: RF modulators region specific??

Hiya,

Yes I did know that (but had forgotten, thanks for reminding me!), the modulator I mentioned only supports L Band 3 not Band 1. I think I read somewhere that Band 1 in France was only used for Canal+ after the 819 had been switched off in 1982.

I bought a working 2001 French spec Sony VCR (SLV-SE810B) which has a programmable L/G UHF modulator from the bay and connected it to my little Panasonic TX-G10 multi-standard CRT. It all works, the audio seems noisy on L though, I suppose that was the use of AM for audio instead of FM. The French later adopted NICAM which would vastly improve things.

Cheers

Patrick
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Old 21st Jun 2016, 1:21 pm   #11
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Default Re: RF modulators region specific??

Patrick,

Yes, you read correctly, L' was used in Band I for Canal+. Most of the time there were scrambled programmes , but some were transmitted in the clear (the news I think was one such programme).
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Old 22nd Jun 2016, 7:27 pm   #12
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Default Re: RF modulators region specific??

I had a BSB Box (ie squarial) in the early 90's that I could use to pick up four french channels in D2-MAC, interesting stuff on Canal+! well in those days anyway.

I have a Fransat cam today on my Samsung TV and Canal + is usually in the clear early evening, discussion programmes and the like.

Patrick
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