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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 9th May 2022, 1:50 pm   #1
inaxeon
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Default Consumer NICAM Modulators. Did any exist?

Hi Folks

I've recently been working on a project to recreate an analogue TV transmission including NICAM audio - just for a laugh.

I bought this Philips PM5687 NICAM modulator to create the NICAM carrier. I've been able to demod its output successfully in software so I think it probably works. Some work to do before that's part of a full vision + FM audio carrier however.

Back to my question though - was there ever a consumer grade product which can create NICAM? Whether it be a VCR, standalone modulator, DVD player etc. I've been searching for hours and have come up with nothing! Just want to be sure I wasn't crazy buying this thing!
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Old 9th May 2022, 2:38 pm   #2
paulsherwin
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Default Re: Consumer NICAM Modulators. Did any exist?

I'm not aware of any such consumer product. There's no need to create a Nicam signal in something like a VCR, only to decode one.
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Old 9th May 2022, 2:48 pm   #3
inaxeon
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Default Re: Consumer NICAM Modulators. Did any exist?

Makes sense. Cheaper to tell people to hook up the SCART cable. It seems that NXP thought there was a need however, they apparently went to the trouble of designing this:

https://www.nxp.com/docs/en/data-sheet/MC44C404.pdf

But I can't find any evidence that it ever went into production...
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Old 9th May 2022, 5:16 pm   #4
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Default Re: Consumer NICAM Modulators. Did any exist?

There were a few devices manufactured by 'a2b Electronics' that were basically multi-tuner Freeview boxes (Multibox 3T and 6T). They could be set up to send a handful of selected Freeview channels out over an analogue UHF feed, for example, in a hotel distribution system.

They definitely had support for NICAM and A2 Stereo, along with some rudimentary Teletext support, such as subtitles and possibly 'Now & Next' info. I've never been able to get my hands on one, unfortunately!
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Old 9th May 2022, 5:25 pm   #5
inaxeon
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Default Re: Consumer NICAM Modulators. Did any exist?

I found that. There is a module from that system for sale on eBay at present, for quite a lot more than I paid for the Philips, granted it's a full solution where as I will have to do video + FM mono separately.
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Old 9th May 2022, 9:29 pm   #6
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Default Re: Consumer NICAM Modulators. Did any exist?

Yes, those modules require specific control software (available here) to set parameters via the serial port. The 'Multibox' units were a little more 'plug 'n' play' in that regard.
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Old 10th May 2022, 8:57 am   #7
Rubberfingers
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Default Re: Consumer NICAM Modulators. Did any exist?

I've no experience of using it, but the HackTV project, using the HackRF SDR appears to incorporate a Nicam 728 encoder https://github.com/fsphil/hacktv
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Old 10th May 2022, 12:01 pm   #8
hamid_1
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Default Re: Consumer NICAM Modulators. Did any exist?

The HackTV project looks interesting, however I do have a couple of commercial devices that can produce TV signals with NICAM audio.

The first is the a2b Multibox micro headend - link to instruction manual here

This is basically a Freeview box with RF modulator including a NICAM encoder. There was a 3-channel version and a 6-channel one. I have the 3-channel one, which receives 3 Freeview channels simultaneously from 2 different multiplexes (e.g. BBC1,BBC2,ITV) and converts them to analogue RF with optional NICAM as well as analogue audio. The a2b Multibox re-creates analogue TV broadcasts, allowing analogue TVs and video recorders to be used just like before the digital switchover. Their original remote controls can be used to change channels, and NICAM-equipped TVs and VCRs will be able to receive and record in stereo.

The a2b Multibox was rather awkward to set up, because by default, it is set to use VHF channel S11 for RF output which most British TVs can't tune in to. I had to find a multi-standard portable TV which could receive the Multibox, then go into the Multibox menu and change the RF output to a UHF channel, then re-tune the TV and select PAL-I & NICAM audio. Once set up, it works quite well.

The a2b Multibox can only receive DVB-T television signals. In the future, if there's a switch to DVB-T2 or some other system, it will become useless. It can't convert anything other than DVB-T to NICAM, so you can't input your own material unless you happen to have a DVB-T modulator.

The other device I have is the Philips PM5518TN TV pattern generator. The TN suffix indicates that it generates teletext and NICAM signals. The Philips PM5518TN produces video out and RF out from a built-in modulator. As well as using the built-in test cards, you can even input your own video and audio signals. Sadly the Philips PM5518TN RF modulator cannot encode analogue audio into NICAM. You can only hear the built-in NICAM test tones. However, I believe it's possible to input externally-encoded NICAM data.

If you just want to see the NICAM light come back on your old TV or VCR, either of the above solutions will work.
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Old 10th May 2022, 4:59 pm   #9
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Default Re: Consumer NICAM Modulators. Did any exist?

Quote:
Originally Posted by hamid_1 View Post
If you just want to see the NICAM light come back on your old TV or VCR, either of the above solutions will work.
Was wanting to do a bit more than that. Actually I don't even have a suitable TV or VCR. Don't really want to fill my lair with old AV gear if I can avoid it. I bought this board off eBay for 3. It's got DQPSK demod, codec, DAC etc. Most of the needed bits.

Was interested to see if I could make it work without whatever it came out of. Needed NICAM signal first though. I have a NICAM signal now, I just need to grapple with the difficulties of building the tuner/IF/AGC etc
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Old Yesterday, 7:38 pm   #10
patrickgnl
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Default Re: Consumer NICAM Modulators. Did any exist?

Quote:
Originally Posted by inaxeon View Post
Quote:
Originally Posted by hamid_1 View Post
If you just want to see the NICAM light come back on your old TV or VCR, either of the above solutions will work.
Was wanting to do a bit more than that. Actually I don't even have a suitable TV or VCR. Don't really want to fill my lair with old AV gear if I can avoid it. I bought this board off eBay for 3. It's got DQPSK demod, codec, DAC etc. Most of the needed bits.

Was interested to see if I could make it work without whatever it came out of. Needed NICAM signal first though. I have a NICAM signal now, I just need to grapple with the difficulties of building the tuner/IF/AGC etc
You may already have a suitable TV. I suspect most modern TV‘s have a NiCAM decoder built into there analogue tuner chipset. Most modern TVs have multistandard (B/G/D/H/I/K/L) analogue tuners, so I would assume can cope with Nicam and the German analogue stereo A2 Zweiton standard.

Agreed a bit hit and miss but worth a try if you can create a generator
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