HDMI Cable Runs

[jonnyf]

Hi all,

Sorry if these are really silly questions, but I've had a look online but just can't get my head round it!

 

Basically, I need to put in a ~40m run of video cable, and the people I'm working with are fairly set on doing it with HDMI. What's the longest cable we can send 1080p down before it needs some sort of boosting - ideally, if we do need something, it wouldn't involve anything 'mid-cable' as that's gonna be in a not very accessible ceiling space, so something at one or both ends?

 

Is there any difference between types of HDMI cable? Is it the case that anything will do as if the signal gets there it gets there - if you know that I mean! Obviosuly there's a bit of difference between this and this!

 

Thanks in advance!

Jon

[J Pearce]

I'm no expert but I'd have thought by 40m you'd be needing to convert to cat5 or fibre for the run and have converters at each end.

The other weeek I was setting up a nice fibre DVI line from XL Video that had the converters built into the DVI shells, so it looked and behaved as a normal DVI cable (apart from needing to get it the right way round) but was fibre for transmission.

[imageman]

CAT5 all the way, I have used the Gefen unit before for sending HDMI over CAT5/6 and they do a top job.

[Nick Mawer]

There are many factors which influence whether an HDMI signal will travel a given length: some of them are

 

1) How stable - jitter free - is your source

2) Whether the receiving device has any re-clocking circuitry

3) The basic quality of the cable - spending a fortune on a cable will not necessarily guarantee significantly better performance

4) The resolution that you are running. Higher resolutions are more prone to problems than lower ones.

 

The HDMI spec was written, as I recall, to send a 1080i or 720p signal up to 15m. Now more capable copper cables should allow you to go 15 - 20m with 1080p.

 

For the distance that you are talking about - 40m, there are a number of possible solutions.

1) a single CAT 6 cable with an active balun at each end. EG Kramer PT-571 and PT-572 http://www.kramerelectronics.co.uk/product...el.asp?pid=1608 maximum distance achieveable approximately 80m (not all CAT 6 cables are the same)

2) a 4LC fibre cable coupled with a single CAT 5 cable, and transmitters and receivers eg Kramer 631R/T http://www.kramerelectronics.co.uk/product...del.asp?pid=464 range limited by copper cable for EDID and handshaking to 100m

3) Hybrid fibre/copper cables like the one that J Pearce mentions - which do have to be installed the correct way round, and should be left in a position where they can easily be retrieved should, for example, an electrical spike take out either end.

4) pure fibre tx and rx units

[sleepytom]

there are some other options too..

 

Blackmagic do a DVI to HDSDI converter - you can either run the HDSDI directly into to the display or into a blackmagic HDLink if your display only has HDMI / DVI. If you use the DVI converter with the HDLink box then you can transmit computer resolutions in addition to the standard HD/SD video formats. This system is good for upto 300m and has the advantage of using standard SDI BNC cable which is cheap and robust.

 

I would steer clear of the cat5/6 products, they don't cope very well with high bandwidth signals and have been to root cause of many problems I've encounter both in installations and tempory installs.

 

I would go either for the blackmagic system or a pure fibre system using foxbox from extron. The foxbox is a better system than the hybred system as you can upgrade / change the signal format by swapping the end boxes - no need to pull the fibre though again.

[jonnyf]

For the distance that you are talking about - 40m, there are a number of possible solutions.

1) a single CAT 6 cable with an active balun at each end. EG Kramer PT-571 and PT-572 http://www.kramerelectronics.co.uk/product...el.asp?pid=1608 maximum distance achieveable approximately 80m (not all CAT 6 cables are the same)

 

Nick - I'm interested in weather this requires a Cat5 or Cat6 cable, your post mentioned Cat6, but the info on the website only mentions Cat5 and claims the product only has a Cat5 connection.

Would you also be able to advise me on rough cost of these units too?

 

Cheers,

Jon

[Nick Mawer]

For the distance that you are talking about - 40m, there are a number of possible solutions.

1) a single CAT 6 cable with an active balun at each end. EG Kramer PT-571 and PT-572 http://www.kramerelectronics.co.uk/product...el.asp?pid=1608 maximum distance achieveable approximately 80m (not all CAT 6 cables are the same)

 

Nick - I'm interested in weather this requires a Cat5 or Cat6 cable, your post mentioned Cat6, but the info on the website only mentions Cat5 and claims the product only has a Cat5 connection.

Would you also be able to advise me on rough cost of these units too?

 

Cheers,

Jon

 

Hi Jonny, the products work over a longer distance using CAT 6. The connection is the same for CAT6 as CAT 5. I can't speak for Sleepytom's experience with CAT 5/6 transmitters receivers, but one thing that I do know is that the technology for these products has got better and better, and the reliability and ease of use is much improved. Be careful with your cabling and test the product with the length of cable that you are planning to use before you run the cable if possible.

The PT-571/2 have a list price in the UK of £149 each ex vat

[sleepytom]

Be aware that some products designed for Cat5 do not perform well on Cat6 cable. I've seen really awful results caused by the wrong type of cable. Decent twisted pair interfaces will come with a recommended cable type, often a specific cable from a specific manufacturer will be recommended in the manual. Save yourself a load of problems by using the recommended cable, rather than the left over drum of random cable that the network guy had knocking about.

 

Nicks advice to check the product works with the cable BEFORE you run the cable in is spot on, though I've seen cases of TP senders working in a test with a long cable in a box, and then failing when the long cable in run in the venue with a load of RF / EMI knocking about.

 

If you can afford to go fibre then you won't regret it.

[Nick Mawer]

Be aware that some products designed for Cat5 do not perform well on Cat6 cable. I've seen really awful results caused by the wrong type of cable. Decent twisted pair interfaces will come with a recommended cable type, often a specific cable from a specific manufacturer will be recommended in the manual. Save yourself a load of problems by using the recommended cable, rather than the left over drum of random cable that the network guy had knocking about.

 

Nicks advice to check the product works with the cable BEFORE you run the cable in is spot on, though I've seen cases of TP senders working in a test with a long cable in a box, and then failing when the long cable in run in the venue with a load of RF / EMI knocking about.

 

If you can afford to go fibre then you won't regret it.

 

It is certainly true to say that many products including our own that are designed for use with CAT 5, don't work very well with CAT 6. However, all our products for sending digital signals over CAT x product work better with CAT 6 and even better with our CAT 7. The most common of the type of problems that Sleepytom refers to, are to do with skew with computer graphics signals. There is more skew on CAT 6 than there is on CAT 5, and therefore the problems of colour separation, that look like the old problem of badly adjusted convergence, are more apparent.

 

Ultimately, Fibre solutions will give you a greater range, but there is, as always, a cost performance trade off.

[sleepytom]

The price gap between fibre and copper is closing, this is made all the more true by needing expensive Cat7 cable to send 1080p even modest distances.

 

Fibre is future proof as it can cope with huge bandwidths well beyond 1080p, you just change the boxes on the end. 1080p is at the very limit of what can go down cat7 so a future upgrade to 2k / 4k / 3d / whatever comes about in the next 5 years will see you having to replace the whole installation with fibre.

 

pre-terminated fibre is pretty cheap now and you don't need expensive tools to install it.