long video runs

[Brian]

I'd think that would be RF though rather than video.

Nope, composite video.

 

There was (still is?) a network of feeds, operated by BT, running the length and breadth of the UK, to carry composite video feeds between studios and other facilities. Central switching at the BT Tower backed up by a few regional centres.

[sleepytom]

when are you talking about? the 80's??

 

to me it seems really strange that composite video would be transmitted around the country like this. It would be very expensive and result in a terrible quality signal, anyone who'd sent composite more than 300 meters will know that it doesn't work very well at all, boosting the signal helps to a degree but you still end up losing quality and getting unreliable sync. Why would they choose composite as part of the transmission chain?

 

I dunno maybe I'm too young to understand this? I've never worked anywhere remotely TV like where composite is in use. Everything is SDI and pretty much always has been in my working lifetime, the only reason I have any experience with non SDI tech is from events work where the budgets are small so old kit gets used.

 

Anyway I'm standing my ground on this one - Today there is no composite infrastructure involved in broadcast TV. Analogue switch off will make this 100% true, the DVB-t signal is encoded directly from a digital SDI signal - the vast majority of programmes will have no analogue signals at any point in their production.

 

Anyway its kind of irrelevant to the OP - you cannot expect to run 800meters of standard BNC and then get a usable quality image from feeding composite down it. Yes it would work if you had ultra high performance cable running in containment away from any noise with optoisolation to remove ground loops, but as a temporary install down a load of cable with barrel joiners etc etc you won't enjoy trying to go further than a couple of hundred meters.

[Brian]

when are you talking about? the 80's??

No, 2001. In 2001 I had a number of composite video circuits installed by BT. You can still do so.

 

...a terrible quality signal, anyone who'd sent composite more than 300 meters will know that it doesn't work very well at all, boosting the signal helps to a degree but you still end up losing quality and getting unreliable sync. Why would they choose composite as part of the transmission chain?

You've obviously never seen it done properly then.

 

Anyway I'm standing my ground on this one - Today there is no composite infrastructure involved in broadcast TV.

Absolute rubbish.

 

...you cannot expect to run 800meters of standard BNC and then get a usable quality image from feeding composite down it.

Ditto.

 

Been there and done it loads of times.

 

Brian

ex-chief engineer for one of the UK's leading video and audio post-production groups.

ex-chief engineer for one of the UK's leading transmission facilities.

ex-chief engineer responsible for launching 14 satellite TV channels.

[sleepytom]

Fair enough..

 

I'm surprised that people were installing composite that late. As I've said my experience in all this is relatively recent and not studio / broadcast backbone based.

 

My bad experiences with medium length composite runs is all event based and is admittedly in noisy environments with dimmer power and less than perfect earthing. I don't doubt that with time, care and good quality components you can send composite over long distances. I suspect that temporary composite installs I've had problems from were down to the domestic nature of the original source - a cheap DVD player probably isn't producing as nice a signal as broadcast centres will and as such will be more susceptible to noise.

 

Sorry about the tone of my previous posts in this thread - I've had a crappy week and this seems to come over in my posting style. I hope not of offended anyone too badly :)

[Starstruck]

Hi , how did this events work out ??

 

Ive just been asked to do an event were there is a need for a 600m video and audio feed .

 

Ive been looking at a bluedelta milestone system to run it over cat 5e.

 

How was the quality ???

 

Im looking at having one camera at one end and two plasmas at the other.

 

Cheers

Kev