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Tech Chat RF Modulators, UHF 625.

4 Posts
4 Users
Illustrious Member
Topic starter

I am going to show my ignorance here and no doubt it has been covered before, but when we were blessed with analogue 625 line transmissions, you could tune through the channels with relative ease and any set would display a perfect picture after an easy to find exact tuning point for any given channel. Well, mostly with a good aerial system.

But with a modulator, including a VCR or whatever, you have two apparent tuning points. The signal seems more spread out and can be prone to patterning or interference. Something to do with single/double sideband? I should know, but can't remember.

So, is it possible to buy a quality modulator that provides a "proper" signal identical to that which would have been recieved off-air during the good old analogue day's?


Posted : 01/08/2022 4:43 pm
Illustrious Member

The problem is indeed cheap modulators being DSB.

It is possible to get proper VSB modulators, but you'll most likely be looking for second-hand Kathrein* professional modulators from cable-type installations. We have some at work for the RF distribution system.

*other brands are available.

Posted : 01/08/2022 5:05 pm
Honorable Member

I'm told the RF modulator from an old Sky+ box is pretty good quality and can be modified by using the datasheet for the chip inside, but I've never tried it so it could be a complete load of tripe.

I can't ever remember using a Sky+ box with RF, I know the first Sky+HD boxes still had RF but the last few didn't. 

Posted : 02/08/2022 8:31 am
Noble Member

I’ve just been looking at a Vision brand VSB modulator and the price is eye watering, also it needs extras. I use a Panasonic VCR, the RF out channel can be set anywhere between 21-68 and can be used as a video switch by selecting any of it’s three AV inputs. I’m very happy with the quality of the output, have a look at my ICC5 below, that is UHF. And as an added bonus it plays my large collection of video tapes.

Posted : 02/08/2022 10:39 am