How hard would it be to create a TV signal amp so I can radiate a TV signal across my room? Used in a setup like this:

Video source——> Modulator ——> Valve amplifier ——> antenna

And then obviously then to an antenna on the back of my TV.

What valves would I use? ECC85s?

Thanks,
Oli

Edit: if my modulator outputs a max of 18 mV, would I even need an amp?

You need a linear wideband VHF amplifier.

Designing and building such a thing using valves is non-trivial.

Why not just obtain an antenna distribution amplifier with a gain of about 30dB and a launch level of 600mV? They must be around as pullouts from old installations.

Something like this?

https://www.aliexpress.com/item/1005008325343097.html

If you've got an old 8-bit computer, they often contained a VHF modulator, for connection to an analogue TV. You might be able to plug the output to a TV antenna instead.

Or, if you've got a working VCR, same thing with that.

He's got the modulator, just wants to boost the output.

For a buck 50, that little module would be hard to pass up. With a 12V supply it should have the headroom.

It would be wise to check its output with a spectrum analyser (if you can borrow one) to make sure you aren't radiating on frequencies where you shouldn't go.

Designing and building such a thing using valves is non-trivial.

I was thinking the same thing. Years and years ago now, they used to make these things called video senders. It was essentially a video and audio transmitter with a range of about 20 metres. They were about the size of a packet of fags with RCA inputs for video and mono audio and they had a single rabbit ear antenna on them and ran from a fleaweight plug pack.

A trimpot on the back let you tune the RF output to between Ch 29 and Ch 40.

I am not sure if they still make them but it might be worth a hunt for. They were about $40 in yesterday's money but if still available I doubt they'd be costing much more than that now.

they used to make these things called video senders

On clearance special at Jaycar:

"This AV sender will allow you to send your pay TV reception (or any other video source) to any part of the house."

https://www.jaycar.com.au/digitech-5-8ghz-wireless-av-sender-receiver-with-wideband-ir-extender/p/AR1913

That may work, it depends on whether the receiving telly is compatible with the receiver on that system.

The ones I was thinking of didn't have a wireless bridge like that one does. The ones I had were like mini TV stations and there was only one box - outputting to a UHF channel, allowing the TV just to pick up the signal from its antenna.

With the demise of analogue broadcasting, there was probably no need for them anymore.

Wow thanks everyone! Very interesting stuff... way before my time!