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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 23rd Nov 2019, 8:45 pm   #1
marsbar
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Default Converting RF TV to direct Video and Audio

For my RV, I wanted to have a Tv that draws little current.

So I have a small decoder that turns DTV to analogue video and audio.

The one B/W TV I had was easily converted, using pin 5 and 9 on an IC (You Tube hint). Unfortunately this TV is very small, say 3" screen. The small analogue tuner and radio tuner was removed as they were obsolete.

So I have another TV. This is 12" b/w. There are two big tuners on the right side, size of a cigarette pack each. One for UHF and one for VHF. The "click" type for VHF.

I do not have a small RF generator, any chance I can tap into the circuit board directly with video and audio signal? Or do the tuner units deliver some sort of baseband so no luck?

Any advise here, is to difficult?
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Old 23rd Nov 2019, 9:06 pm   #2
G6Tanuki
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Default Re: Converting RF TV to direct Video and Audio

Would it not be easier to use a cheap 'tablet' computer [which will give you at least a 10-inch screen] and plug in something like a Now-TV USB receiver-stick?

[I don't know what you have as TV signals in your locality or where you might roam in your RV: roamers here in the UK generally use satellite-TV because it is more reliable when you're parked up in a distant/deep valley]
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Old 23rd Nov 2019, 11:27 pm   #3
cheerfulcharlie
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Default Re: Converting RF TV to direct Video and Audio

Something like this modulator

https://tinyurl.com/sc67r5y

would allow you to connect directly from your modern equipment
to the aerial socket on your old tv without going inside.

Apparently runs 0n 5v DC so would probably need a 12v to 5v converter if you are going to run it in an RV

Last edited by cheerfulcharlie; 23rd Nov 2019 at 11:39 pm.
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Old 24th Nov 2019, 12:15 am   #4
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Default Re: Converting RF TV to direct Video and Audio

I've been tempted to buy one of these but can't see a full spec, especially the output channel.
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Old 24th Nov 2019, 10:05 am   #5
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Default Re: Converting RF TV to direct Video and Audio

It is actually very easy to couple into the video circuitry of a TV, to inject a composite video signal, and couple into the audio circuitry to inject an audio signal to turn the TV into a "video monitor".

Sure you can get your video and audio signals, feed them to an RF modulator and then feed that to the TV as an RF signal at the antenna input, as has been suggested, but the quality loss is pretty severe. Maybe you can tolerate that.

In fact , back in the mid 1970s' when TV's were cheap, but video monitors with composite video inputs and line audio inputs were expensive, many home computer enthusiasts modified the TV sets to receive video inputs to save themselves a truckload of cash.Even one of the first video arcade games, Atari's Pong 1972, had inside it no more than an off the shelf Hitachi TV set , modified to have video & audio inputs.

Its fairly easy on the audio side, you can usually just inject the audio at the top leg of the volume control normally and disconnect or disable the TV's audio detector/IF so you don't get hiss mixed in or disconnect the top leg from the feed in the TV set.

In the video circuit (of the particular set) you need to look at the output of the video IF & detector and work out the polarity of the video signal there and where the sync is taken off so you can inject your video signal (typically 1V pp terminated) into the correct part of the circuit with the correct polarity and so the H & V sync are stripped off downstream of that point in the circuit.

So clearly, as many questions like yours dictate, you will require the schematic of your set unless you are prepared to trace it out (which I have done many times when the schematic is not available)

To help with the many iterations that are possible with this solution, Don Lancaster wrote an article about it in Byte magazine 1975. It is reprinted in this computer manual, you will have to scroll to page 234 of the page numbers on the pdf not the document page numbering. The article is called "Television Interface":

https://deramp.com/downloads/process...s%20Manual.pdf

Hugo.
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Old 24th Nov 2019, 10:14 am   #6
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Default Re: Converting RF TV to direct Video and Audio

Quote:
Originally Posted by G6Tanuki View Post
Would it not be easier to use a cheap 'tablet' computer
+1

I am currently in Spain and find this is a good way to get TV reception. I am using "TVMucho" to access British freeview channels. On a pay as you go basis this costs me 12 euros / month. Despite the title this not limited to Spain.

A more limited range of channels is available on an Android app "UK TV Radio"
which is free and gives me a 3" HD display on my phone.

Peter

Last edited by peter_scott; 24th Nov 2019 at 10:20 am.
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Old 24th Nov 2019, 11:25 am   #7
tony brady
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Default Re: Converting RF TV to direct Video and Audio

when I'm in France I use a Humax box set up in the UK to get freesat. the only costs were for the dish and the box.
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Old 24th Nov 2019, 11:40 am   #8
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Default Re: Converting RF TV to direct Video and Audio

Quote:
I've been tempted to buy one of these but can't see a full spec, especially the output channel.
This could be a handy device, looks like a good bit of kit to watch programmes stored on a laptop straight to any 625 line TV with only RF input.
I think this will go on my Christmas list!

Mark
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Old 24th Nov 2019, 12:10 pm   #9
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Default Re: Converting RF TV to direct Video and Audio

I've ordered one of these units and will report back my findings when it arrives.

DFWB.
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Old 24th Nov 2019, 12:23 pm   #10
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Default Re: Converting RF TV to direct Video and Audio

One of the many adverts notes an output around 61Mhz, but of course others could be UHF.
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Old 24th Nov 2019, 2:54 pm   #11
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Default Re: Converting RF TV to direct Video and Audio

That looks a handy litttle box! As the OP is only using a small black and white TV, I wouldn't think up-converting to RF would show much loss in quality, and would be a nice easy 'off the shelf' solution.
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Old 24th Nov 2019, 3:17 pm   #12
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Default Re: Converting RF TV to direct Video and Audio

Quote:
Originally Posted by FERNSEH View Post
I've ordered one of these units and will report back my findings when it arrives.

DFWB.
I thought it was worth a punt at 13 quid instead of the effort of prodding around in an old TV that might have a live chassis.

It may/may not have some short comings but still in awe of the Chinese who could make it for 13 let alone sell it for that price..I mean it even has a remote control LOL
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Old 25th Nov 2019, 10:27 am   #13
mark pirate
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Default Re: Converting RF TV to direct Video and Audio

Quote:
I've ordered one of these units and will report back my findings when it arrives.
I notice there is a similar unit with remote control, this has a button to adjust the output channel, so have ordered one

Had to laugh at the "Analog TV transmitter" logo on the top, but hopefully it will be a useful bit of kit.

Mark
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Old 25th Nov 2019, 11:01 pm   #14
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Default Re: Converting RF TV to direct Video and Audio

Sounds interesting, any chance of a link?
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Old 26th Nov 2019, 6:06 pm   #15
marsbar
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Default Re: Converting RF TV to direct Video and Audio

I allready have an RF converter, PLL. LED display. But very big! Found this:

https://www.ebay.co.uk/itm/Mini-AV-R.../163877599951?

This is probably a small circuit board I could built into the TV itself.
Problem is that I have no idea of the quality of this item. I bought a TV modulator before, but it was a scam as the unit hade a "hobby ciruit inside" and lethal power supply... so maybe better to stay away?
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Old 26th Nov 2019, 6:37 pm   #16
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Default Re: Converting RF TV to direct Video and Audio

It doesn't have a power supply, it needs an external one, so that would be a separate issue.
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Old 27th Nov 2019, 12:20 am   #17
Richard_FM
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Default Re: Converting RF TV to direct Video and Audio

I think it can be powered from a USB supply.

Also it only operates on VHF frequencies, so not much use for most UK 625 line set.
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Old 27th Nov 2019, 2:19 pm   #18
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Default Re: Converting RF TV to direct Video and Audio

Quote:
Sounds interesting, any chance of a link?
Your wish is my command

https://www.ebay.co.uk/itm/HDMI-RF-C...r/193109503814


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Old 27th Nov 2019, 11:54 pm   #19
Richard_FM
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Default Re: Converting RF TV to direct Video and Audio

Thanks, there seems to be quite a few different seller offering these, which seem to be the same spec.
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Old 28th Nov 2019, 2:30 pm   #20
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Default Re: Converting RF TV to direct Video and Audio

Thee is another HDMI-RF modulator numbered HDM 68 which be set to many different analogue systems & frequencies, but is slightly more expensive at around 23.
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