Are there any Composite to UHF Multi-Modulators? - UK Vintage Radio Repair and Restoration Discussion Forum

Lantizia · 14th Apr 2025, 5:12 pm

Hey,

So I'm about to get an old TV delivered on Wednesday that will only have an aerial / UHF socket on the back for PAL reception only... no composite input or anything else. I know that I could possibly modify the TV to add composite... but it would loose its charm then!

I've spotted you can get TV UHF Modulators that take Composite input (e.g. 3 x RCA plugs for audio/video, or SCART, or S-Video) and BINGO you've got a frequency to tune into on your TV...

But this TV has 12 buttons on the front, for a max of 12 channels that you can tune into... and I want to be able to select what to watch from that

Basically I want to be click happy pressing buttons on the front of my TV!

There does seem to be some of these modulator devices with multiple inputs... but they've usually got a screen or buttons on the device itself to pick which thing to modulate... so therefore it only does one at a time.

I'm after something that has multiple modulators in one device, where each can operate on a different frequency.

Come up empty finding something at the moment, any ideas? Maybe I'm using the wrong terms?

Thanks

G6Tanuki · 14th Apr 2025, 8:05 pm

In times past there were devices intended for use in hotels and motels that took either RF PAL style audio or composite and remodulated them to be fed into the equivalent of a captive cable TV space.

The better ones had the ability to deliver a default "Hotel" channel with details of things like how to get room service.

And/or a path from the room TV back to the headend, so you could pay for access to a range of adult content or MTV.

These sort of systems were generally stripped out a couple of decades back when digital TV became the norm, but you might be able to find something legacy that would take a bunchof composite or SCART feeds and remodulate them on to UHF PAL.

SiriusHardware · 15th Apr 2025, 9:54 am

There are two stages to this question, one is how to generate / obtain the source material. Maybe the cheapest form of DVB TV tuner is one of these:-

https://www.amazon.co.uk/Melopero-Raspberry-DVB-TV-uHAT/dp/B07JKH36VR

..fitted to a Raspberry Pi Zero - they are probably cheap enough that you could parallel up three or four each tuned to a different DVB channel, and apply their individual composite video outputs to the inputs of a multi channel composite-to-analogue TV modulator. But then you'd have to find such a modulator, ex-hotel perhaps.

AndiiT · 15th Apr 2025, 7:05 pm

Hi, in the past I have used a Multiview T35 modulator, which receives Freeview channels and then re-transmits (user programmed) channels on five analogue frequencies.
I've had a search on eBay but can't find any for sale at the moment, however they do crop up occasionally. There's some more information here if you can access it.

Andrew

arjoll · 15th Apr 2025, 7:53 pm

It looks like there are a number on Aliexpress, up to 16 channels for around NZD$300. No idea how good they'd be, but the normal sources like Hills look to be all digital now.

Lantizia · 15th Apr 2025, 7:58 pm

For now I've gone ahead and bought a used SLX 27851HS which has... 2 x audio RCA inputs (for stereo), 1 x video composite input, and 1 x SCART. Although it'll only do one input/frequency at a time (which isn't what I was looking for really)... it'll do for now to test the TV. I could always use multiple of these and stack them together if needed (as it's got both UHF input and output).

I was thinking each input might be a different bit of retro kit I've got around the room (home computers, DVD players, old PC's, stuff like that).

SiriusHardware: It's interesting you mentioned the fun possibility of doing a multi-channel DVB-T to UHF solution... it wasn't actually part of my question! But it's a happy accident that you bring it up anyway, as I had also been considering this too.

Also... that Raspberry Pi HAT... that's incredibly cheap and I had no idea about that! Thanks for mentioning it.

AndiiT: I'll look out for that Multiview T35 that you mentioned... could be a nice way to simulate that 90's TV experience of 5 channels

Although part of me thinks it might be more interesting to find old footage on a loop instead

Currently the way we do DVB-T in our home is via a quad tuner HD HomeRun box that we just access via RTSP on the network. I guess I could make a device with 4 composite outputs (e.g. an old quad display graphics card) and have each screen playback a different RTSP stream with VLC or something

... but we'd still be back to needing 4 modulators or a multi-modulator with 4 inputs

arjoll: I'll try to see if I can see that... any makes/models to look for?

Maarten · 21st Apr 2025, 10:57 am

Stacking multiple modulators is how it was done in the past, really nothing wrong with that though it would be much more convenient to have multiple modulators in one device. I don't know which model to look for but surely something will turn up sooner or later.

G6Tanuki · 21st Apr 2025, 1:49 pm

If you do want to stack multiple modulators, don't simply link them in series through their RF in and out sockets.

Instead, use proper signal combiners (not the cheapest resistive types).

Many modulators, like old VHS players, have a little amplifier in the pass-through signal path, the effects of several strong signals building up through successive amplifiers and intermodulating along the way can result in a truly horrible spectral mess being presented to the TV.

SiriusHardware · 21st Apr 2025, 2:42 pm

For the modulators, could you just use multiple individual 'metal can' modulators of the type commonly found in home computers like the Sinclair Spectrum, like the ASTEC UM1233? 5V powered, composite colour video in, modulated UHF out.

If combining more than one, all but one would need to be retuned to different UHF output channels and ideally their RF output signals would need to be properly combined before being fed to the single aerial input of the TV. I don't know how much +/- channel tuning range modulators of this type had?

SiriusHardware · 22nd Apr 2025, 7:01 pm

Lantizia, you mentioned 'clicking buttons' by which I took you to mean that the TV does not have a remote.

If it does have a remote that allows for the possibility of a single DVB tuner with composite output, plus a single composite to RF modulator PLUS an I/R receiver / translator / retransmitter unit

The idea would be that you first tune all of the TV's analogue channels to the frequency of the single UHF modulator, so no matter which channel you choose on the TV using the TV's remote, the TV sees whatever is coming out of the DVB receiver.

But then you also introduce a device which 'knows' the remote commands of the original TV remote and retransmits them as the equivalent commands for the DVB receiver.

So you press '1' on the TV's remote, it changes the TV to channel 1, which is tuned to the output of the single modulator. The '1' keypress is also picked up by the I/R translator which retransmits it, once you let go of the button on the remote, in the DVB receiver's expected remote format for a '1' keypress, so the DVB receiver also changes to its channel 1, which might typically be tuned to BBC1.

Press '2' on the TV remote, the TV changes to channel 2 which is also tuned to the output of the modulator, but the command is picked up by the translator which then changes the channel on the DVB receiver to channel '2', which might be tuned to BBC2, so now BBC2 appears on channel 2 on the TV.

You get the idea - this might seem complicated but if you dabble in Arduino there is a very good 'IR' library which I've used in the past which makes receiving and sending IR codes pretty easy, you just need to be able to write a little bit of code to implement the translator functionality - On receiving one specific I/R code, transmit another specific I/R code.

Part of the I/R library's function is to identify the format and content / code of any I/R signals being received and you just need to wire a self contained three-terminal I/R receiver to the Arduino to get that part working.

Of course if the TV is so primitive that it doesn't have a remote, then none of the above applies.

Lantizia · 23rd Apr 2025, 5:46 pm

Nah no remote... doesn't even have an IR receiver on the front.

So it'd have to be a multi-modulator which can do them simultaneously. Tbh I'm not sure if I care about DVB-T... but id instead try to "create" 5 TV channels from old footage instead.

SiriusHardware · 23rd Apr 2025, 8:35 pm

Raspberry Pi Zeros, although they don't have a video-out connector by default, do have a composite output - it's on two unpopulated pads on the PCB - so they could be pretty cheap video file player sources for the inputs of your hypothetical multi-channel modulator.

I might be behind the times and maybe there are even cheaper purpose made video player 'podules' with an SD card slot, a rudimentary user interface and composite-out?

14th Apr 2025, 5:12 pm	#1
Lantizia Triode Join Date: Dec 2022 Location: Newcastle-under-Lyme, Staffordshire, UK. Posts: 10	Are there any Composite to UHF Multi-Modulators? Hey, So I'm about to get an old TV delivered on Wednesday that will only have an aerial / UHF socket on the back for PAL reception only... no composite input or anything else. I know that I could possibly modify the TV to add composite... but it would loose its charm then! I've spotted you can get TV UHF Modulators that take Composite input (e.g. 3 x RCA plugs for audio/video, or SCART, or S-Video) and BINGO you've got a frequency to tune into on your TV... But this TV has 12 buttons on the front, for a max of 12 channels that you can tune into... and I want to be able to select what to watch from that Basically I want to be click happy pressing buttons on the front of my TV! There does seem to be some of these modulator devices with multiple inputs... but they've usually got a screen or buttons on the device itself to pick which thing to modulate... so therefore it only does one at a time. I'm after something that has multiple modulators in one device, where each can operate on a different frequency. Come up empty finding something at the moment, any ideas? Maybe I'm using the wrong terms? Thanks

14th Apr 2025, 8:05 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 15,904	Re: Are there any Composite to UHF Multi-Modulators? In times past there were devices intended for use in hotels and motels that took either RF PAL style audio or composite and remodulated them to be fed into the equivalent of a captive cable TV space. The better ones had the ability to deliver a default "Hotel" channel with details of things like how to get room service. And/or a path from the room TV back to the headend, so you could pay for access to a range of adult content or MTV. These sort of systems were generally stripped out a couple of decades back when digital TV became the norm, but you might be able to find something legacy that would take a bunchof composite or SCART feeds and remodulate them on to UHF PAL. __________________ Let's Degauss.

15th Apr 2025, 9:54 am	#3
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 13,872	Re: Are there any Composite to UHF Multi-Modulators? There are two stages to this question, one is how to generate / obtain the source material. Maybe the cheapest form of DVB TV tuner is one of these:- https://www.amazon.co.uk/Melopero-Raspberry-DVB-TV-uHAT/dp/B07JKH36VR ..fitted to a Raspberry Pi Zero - they are probably cheap enough that you could parallel up three or four each tuned to a different DVB channel, and apply their individual composite video outputs to the inputs of a multi channel composite-to-analogue TV modulator. But then you'd have to find such a modulator, ex-hotel perhaps.

15th Apr 2025, 7:05 pm	#4
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,828	Re: Are there any Composite to UHF Multi-Modulators? Hi, in the past I have used a Multiview T35 modulator, which receives Freeview channels and then re-transmits (user programmed) channels on five analogue frequencies. I've had a search on eBay but can't find any for sale at the moment, however they do crop up occasionally. There's some more information here if you can access it. Andrew

15th Apr 2025, 7:53 pm	#5
arjoll Dekatron Join Date: May 2006 Location: Invercargill, New Zealand Posts: 3,685	Re: Are there any Composite to UHF Multi-Modulators? It looks like there are a number on Aliexpress, up to 16 channels for around NZD$300. No idea how good they'd be, but the normal sources like Hills look to be all digital now.

15th Apr 2025, 7:58 pm	#6
Lantizia Triode Join Date: Dec 2022 Location: Newcastle-under-Lyme, Staffordshire, UK. Posts: 10	Re: Are there any Composite to UHF Multi-Modulators? For now I've gone ahead and bought a used SLX 27851HS which has... 2 x audio RCA inputs (for stereo), 1 x video composite input, and 1 x SCART. Although it'll only do one input/frequency at a time (which isn't what I was looking for really)... it'll do for now to test the TV. I could always use multiple of these and stack them together if needed (as it's got both UHF input and output). I was thinking each input might be a different bit of retro kit I've got around the room (home computers, DVD players, old PC's, stuff like that). SiriusHardware: It's interesting you mentioned the fun possibility of doing a multi-channel DVB-T to UHF solution... it wasn't actually part of my question! But it's a happy accident that you bring it up anyway, as I had also been considering this too. Also... that Raspberry Pi HAT... that's incredibly cheap and I had no idea about that! Thanks for mentioning it. AndiiT: I'll look out for that Multiview T35 that you mentioned... could be a nice way to simulate that 90's TV experience of 5 channels Although part of me thinks it might be more interesting to find old footage on a loop instead Currently the way we do DVB-T in our home is via a quad tuner HD HomeRun box that we just access via RTSP on the network. I guess I could make a device with 4 composite outputs (e.g. an old quad display graphics card) and have each screen playback a different RTSP stream with VLC or something ... but we'd still be back to needing 4 modulators or a multi-modulator with 4 inputs arjoll: I'll try to see if I can see that... any makes/models to look for?

21st Apr 2025, 10:57 am	#7
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,775	Re: Are there any Composite to UHF Multi-Modulators? Stacking multiple modulators is how it was done in the past, really nothing wrong with that though it would be much more convenient to have multiple modulators in one device. I don't know which model to look for but surely something will turn up sooner or later.

21st Apr 2025, 1:49 pm	#8
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 15,904	Re: Are there any Composite to UHF Multi-Modulators? If you do want to stack multiple modulators, don't simply link them in series through their RF in and out sockets. Instead, use proper signal combiners (not the cheapest resistive types). Many modulators, like old VHS players, have a little amplifier in the pass-through signal path, the effects of several strong signals building up through successive amplifiers and intermodulating along the way can result in a truly horrible spectral mess being presented to the TV. __________________ Let's Degauss.

21st Apr 2025, 2:42 pm	#9
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 13,872	Re: Are there any Composite to UHF Multi-Modulators? For the modulators, could you just use multiple individual 'metal can' modulators of the type commonly found in home computers like the Sinclair Spectrum, like the ASTEC UM1233? 5V powered, composite colour video in, modulated UHF out. If combining more than one, all but one would need to be retuned to different UHF output channels and ideally their RF output signals would need to be properly combined before being fed to the single aerial input of the TV. I don't know how much +/- channel tuning range modulators of this type had?

22nd Apr 2025, 7:01 pm	#10
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 13,872	Re: Are there any Composite to UHF Multi-Modulators? Lantizia, you mentioned 'clicking buttons' by which I took you to mean that the TV does not have a remote. If it does have a remote that allows for the possibility of a single DVB tuner with composite output, plus a single composite to RF modulator PLUS an I/R receiver / translator / retransmitter unit The idea would be that you first tune all of the TV's analogue channels to the frequency of the single UHF modulator, so no matter which channel you choose on the TV using the TV's remote, the TV sees whatever is coming out of the DVB receiver. But then you also introduce a device which 'knows' the remote commands of the original TV remote and retransmits them as the equivalent commands for the DVB receiver. So you press '1' on the TV's remote, it changes the TV to channel 1, which is tuned to the output of the single modulator. The '1' keypress is also picked up by the I/R translator which retransmits it, once you let go of the button on the remote, in the DVB receiver's expected remote format for a '1' keypress, so the DVB receiver also changes to its channel 1, which might typically be tuned to BBC1. Press '2' on the TV remote, the TV changes to channel 2 which is also tuned to the output of the modulator, but the command is picked up by the translator which then changes the channel on the DVB receiver to channel '2', which might be tuned to BBC2, so now BBC2 appears on channel 2 on the TV. You get the idea - this might seem complicated but if you dabble in Arduino there is a very good 'IR' library which I've used in the past which makes receiving and sending IR codes pretty easy, you just need to be able to write a little bit of code to implement the translator functionality - On receiving one specific I/R code, transmit another specific I/R code. Part of the I/R library's function is to identify the format and content / code of any I/R signals being received and you just need to wire a self contained three-terminal I/R receiver to the Arduino to get that part working. Of course if the TV is so primitive that it doesn't have a remote, then none of the above applies. Last edited by SiriusHardware; 22nd Apr 2025 at 7:30 pm.

23rd Apr 2025, 5:46 pm	#11
Lantizia Triode Join Date: Dec 2022 Location: Newcastle-under-Lyme, Staffordshire, UK. Posts: 10	Re: Are there any Composite to UHF Multi-Modulators? Nah no remote... doesn't even have an IR receiver on the front. So it'd have to be a multi-modulator which can do them simultaneously. Tbh I'm not sure if I care about DVB-T... but id instead try to "create" 5 TV channels from old footage instead.

23rd Apr 2025, 8:35 pm	#12
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 13,872	Re: Are there any Composite to UHF Multi-Modulators? Raspberry Pi Zeros, although they don't have a video-out connector by default, do have a composite output - it's on two unpopulated pads on the PCB - so they could be pretty cheap video file player sources for the inputs of your hypothetical multi-channel modulator. I might be behind the times and maybe there are even cheaper purpose made video player 'podules' with an SD card slot, a rudimentary user interface and composite-out?