Questions about Analogue TV Distribution

[JohnW2]

hopefully by that time multichannel analogue-to-DTTV converter headends will be cheap enough, although I suspect that IP video will become mainstream.

Indeed. The day will obviously come when analogue RF distribution (and, eventually, even 'TVs as we know them') will be resigned to history, but it should be sustainable for a long time for those who so wish. Indeed, I dare say that a good few TVs with analogue tuners will still be 'going strong' a decade or two after they cease to be manufactured.

Kind Regards, John

 

[Peet]

1...I can’t work out whether (m)any new TVs (apart from very small ‘portable’ ones) now being sold actually have analogue tuners. The specifications very rarely, if ever, mention analogue tuners, and I wonder whether this is because they are invariably absent, or because they don’t bother mentioning them! On the face of it, apart from a few people like me (and maybe some using ancient recorders/players etc. which only have analogue outputs), I can’t see why anyone in the UK would want to buy a TV with an analogue tuner these days.

I haven't kept pace with the developments in tuners as digital has taken hold. For years I could of answered the question outright but sadly not now. You have all the TVs that have been around during the changeover that will be certainly dual standard. Like SimonH2 was saying they're made for a wide market and the chipsets will often have dual uses. (a classic example being PAL/NTSC and SECAM in the color sections of later gen analogue TVs). I would guess that the analogue frontend will actually persist due to bandwidth considerations during digital transmission, but at what point the ability to strip out an analogue TV channel is lost I'm not sure.

One thought - If you're trying to find a modern TV which will also accept analogue RF in, is to take with you an old VCR (some even had a test pattern gen built in on a switch at the back for setup purposes) or maybe a little test pattern generator with RF out on it (sometimes they come up for buttons on ebay, sadly I've just binned an old Philips PM5519!) and try it in the shop with the TV you're thinking of buying.

2...If, as I suspect, the answer to (1) is that few, if any, come with analogue tuners, are there any (ideally cheap and physically small!) ‘converters’ (essentially analogue tuners) around which will convert analogue RF into something (composite, HDMI, SCART or whatever) that can be plugged into a modern TV?

If you did go that route ....... The old analogue RF did ok with standard coax plugs on. When you're moving over to other uses of the cable keep your eye on signal quality of the coax connectors. Somes their intermittent connection on some of them leads to unpredictable behaviour for some stuff. Like Sky box remote 'eyes', they inject DC onto the cable to run the remote eye. If the connection (usually the middle pin) on the coax connector is dicky then the RF gets there but the DC doesn't and the eye doesn't work.
Alternatives would be F connectors or possibly one of the BNC types but it would depend on what came on the boxes.

If you did go for HDMI on RF looking at the max cable lengths some of HDMI transceivers them will achieve (limited to 200-300ft) suggests that the coax cable bandwidth is fairly well used. So depending on your run lengths, and existing cable spec, to use them at distance could be problematic. You'd need to decide what version of HDMI you would want to transmit and its bandwidth then the attenuation of the installed cable, then what the boxes are capable of (ie how much attenution can they stand before they fall over). Plus for HDMI you'd need a back channel for control of the source to be able to switch what was coming through if that's a requirement.
Look at this cable & its datasheet for representative data on losses in typical coax cable. http://uk.farnell.com/pro-power/268770/cable-coax-tv-75r-per-m/dp/3855429

How many cars state (in the specs) that they have four wheels ?

That did make me laugh, but so true.

Actually, I can now think of a couple of tellies that I've seen without analogue tuners - but they were high-end monitors supplied with a video conferencing system with no tuners at all (it was an option, as was satellite, and a load of other stuff), and it was well before DVB was heard of.

Monitors with no tuners and video sources with no RF modulators were very common in the broadcast industry. Sometimes the better they were the less likely they were to have a tuner/modulator. They had no place as quality of picture was the overiding criteria, and if you wanted to screw a picture stick it through a modulator/tuner. I have a SVHS video machine here that was shockingly expensive in the 90s (yours for now circa £10 on ebay) which has most baseband sources out the back but no tuner. It was an optional extra.

One good reason to keep an analogue TV displaying a digital picture is that I've found that a decent analogue TV monitor with a freeview box in through SCART does a much better job of the picture than most current modern digital TVs do. After looking at loads of them in shops I came to the conclusion that the chipsets doing the actual screen driving were both too slow and often driving LCD panels that were not up to the job having a poor colour gamut. It was only the highend TVs that did both something like properly.

Some stuff I came across whilst googling

Not sure how much use it might be but for Freeview tech info look at http://www.dtg.org.uk/publications/books.html

http://en.wikipedia.org/wiki/HDMI is useful too.

http://www.hdmi.org/prodFinder/ProductSearch.aspx maybe useful.

http://www.avsforum.com/t/996218/how-to-calculate-hdmi-bandwidth

http://www.avforums.com/forums/vide...-convert-hdmi-rf-coaxial-i-want-analogue.html

 

[JohnW2]

I haven't kept pace with the developments in tuners as digital has taken hold. For years I could of answered the question outright but sadly not now. You have all the TVs that have been around during the changeover that will be certainly dual standard. ... I would guess that the analogue frontend will actually persist ...

Very many thanks for your interest and detailed response. As you will have seen, after an unlucky false start (the first handful of manuals I looked at making no reference to analogue), I’ve now satisfied myself that at least a high proportion, probably the majority, of TVs currently on sale do contain analogue tuners, even though it’s not mentioned in the ‘spec’.

One thought - If you're trying to find a modern TV which will also accept analogue RF in, is to take with you ... or maybe a little test pattern generator with RF out on it ...

Yes, just in case there is any doubt from the documentation, I’ll probably do that. I have at least a couple RF-out pattern generators in some dusty corner of one of my tool boxes, and I would hope that at least one of them still works!

2... ... are there any (ideally cheap and physically small!) ‘converters’ (essentially analogue tuners) around which will convert analogue RF into something (composite, HDMI, SCART or whatever) that can be plugged into a modern TV?

If you did go that route ....... The old analogue RF did ok with standard coax plugs on. When you're moving over to other uses of the cable keep your eye on signal quality of the coax connectors.

With those approaches (had I needed them), the coax would still be only carrying RF – the output of the converter (local to the remote TV) would be something (e.g. SCART) other than coax. However, I certainly agree with you about the iffiness of standard coax connectors. I was brought up, starting around 50 years ago, to always solder the tip of the centre conductor into a plug (interesting exercise, given that the metal {nickel-plated?} didn’t like being soldered to, and the insulating collar melted very easily!). I still do, if I can, but am often thwarted by blind-ended pins (even if they do have a tiny screw).

How many cars state (in the specs) that they have four wheels ?

That did make me laugh, but so true.

You say that, but the specs (for TVs) often do include many things that are seemingly as obvious as the 4 wheels of a car (e.g. speakers, remote control, even ‘aerial socket’ or 'power input socket'!!)

Thanks again.

Kind Regards, John