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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 18th Mar 2022, 7:41 pm   #1
lloydwells
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Default TV pantry transmitter

I'll freely admit TVs are not really my bag I have two 405 line sets that are up and working and that'll do me however I came across this article / design for a tiny TV transmitter and wondered if anyone had a design for anything like it ( this rather annoyingly doesn't have a schematic ) essentially a Pantry transmitter for TV I'd like to build something like this so I can use both TVs without having to lug about the digital receiver, aurora and pile of cables between TVs.
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Old 18th Mar 2022, 9:50 pm   #2
19Seventy7
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Default Re: TV pantry transmitter

I don't have any info on an actual purpose built transmitter unfortunately, but I do know if you put several TV boosters in series with one another and an indoor aerial on the end you can build a transmitter like that, though you'll probably need 3 or 4 boosters for a half decent picture...
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Old 18th Mar 2022, 10:04 pm   #3
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Default Re: TV pantry transmitter

Hi.
This thread of mine, https://www.vintage-radio.net/forum/...d.php?t=185308 (a few down from this one) shows a simple valve modulator, Feeding the output to an old rabbits ears antenna it is usable up to just about 10 meters before it gets too weak.
I've not done any more to this recently as I've been very busy.
I also tried a mod to my EH90 pantry transmitter many years ago and got similar range on 45mhz.
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Old 18th Mar 2022, 10:33 pm   #4
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Default Re: TV pantry transmitter

The link to details of the one in the OP's post is https://anarchy.translocal.jp/microt...edTVTX_p0.html - do note that the pictures are the schematic.

Also the part shown in the OP's post is only the audio stage, the rest is in the above link.

A quick 'net search with "DIY TV transmitter" will bring in plenty more results.
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Old 18th Mar 2022, 11:12 pm   #5
lloydwells
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Default Re: TV pantry transmitter

Ahh now I couldn't find the full version. Now I'm wanting to use this on a TV22 so what's got me here is I'm going to need this thing to chuck out what frequency for it and how do I achieve that also the blurb says the sound carrier is 4.5mhz above the video wouldnt it need to be 5mhz ish below the video
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Old 19th Mar 2022, 8:07 am   #6
Dave Moll
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Default Re: TV pantry transmitter

Yes, with the old 405-line standard the sound carrier was indeed 4.5MHz below the vision, so channel 1 was 41.5MHz sound and 45MHz vision - both AM and with positive modulation on the video.
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Old 19th Mar 2022, 10:42 pm   #7
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Default Re: TV pantry transmitter

One of the motivations behind the close down of analogue TV was the opportunity for the government to flog off the large tracts of liberated spectrum. They made a lot of money off the 3G sell-off and think they can have it all over again.

So, many of the channels used by analogue TVs will go to all sorts of services, and distributed across the land. Any rogue signals are going to be fairly likely noticed and complaints made, and official visits set in motion. No-one may want medium wave, but VHF/UHF are hotly contested.

Chains of amplifiers are not easy to do. They go unstable unless a lot of care and checking is undertaken. They could hoot on any frequency, and also give a wide range of harmonics. Oscillations normally build up until the non-linearity of devices limit them, this means that oscillations tend to be at the full saturated power level of the amplifiers used - many times the power they would be run at for good linear operation. Messy!

I think it's much safer to just have a distribution splitter and a run of coax to each set.

Thinking of that, TV sets need appreciably larger signal levels than simple radios, and you'd need an antenna on top of every set.

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