General : Fibre Optic Cable Wire

[leeandrewsmith19]

Hello I was wondering if anybody could help me. I'm looking for a cable to connect my virgin modem to the box on the wall. if this cable suitable for the job I posted in a link? and if not where can i find the cable i need please.

http://www.ebay.co.uk/itm/10M-Satell...item4160082e02

Thank you for your help

[craigj2k12]

yeah thats fine for the job, how come its not already connected?

The eBay seller probably forgot to include it in the box ...

[leeandrewsmith19]

Hello and thank you for you're help. it is already installed but i'm moving stuff around and the wire i have isnt long enough.

Right ... in which case, only buy the length you need for the job. Don't buy a 10 metre cable unless that's the length you need. Altering your cable lengths by too much can affect your signal levels and disrupt your service. If it results in you calling them out, you will get charged for it.

You should be ok, but be aware.

[AndyCalling]

Originally Posted by Chris

Right ... in which case, only buy the length you need for the job. Don't buy a 10 metre cable unless that's the length you need. Altering your cable lengths by too much can affect your signal levels and disrupt your service. If it results in you calling them out, you will get charged for it.

You should be ok, but be aware.

Just out of curiosity, because I can't really understand what you're saying, could you explain this? I don't understand how cutting a cable down can reduce its ability to carry a signal unless one damages it in some clumsy way whilst doing the job. I would have thought a shorter cable would actually be less lossy?

How much can one safely cut this cable back by? It would be a useful measurement to note down.

I feel I ought to be better informed in case I ever get round to trimming back the over large cable VM installed my box with. Well, I thought it was over long at the time but he had it already made up in stock in the van so he used it. Now I'm starting to think it might actually be the minimum length cable that the system can tollerate, and that it only seems long because my Shub is right next to the terminal.

[jb66]

A shorter cable would give you a higher signal than a longer one, your talking marginal differences

Originally Posted by AndyCalling

Just out of curiosity, because I can't really understand what you're saying, could you explain this? I don't understand how cutting a cable down can reduce its ability to carry a signal unless one damages it in some clumsy way whilst doing the job. I would have thought a shorter cable would actually be less lossy?

How much can one safely cut this cable back by? It would be a useful measurement to note down.

I feel I ought to be better informed in case I ever get round to trimming back the over large cable VM installed my box with. Well, I thought it was over long at the time but he had it already made up in stock in the van so he used it. Now I'm starting to think it might actually be the minimum length cable that the system can tollerate, and that it only seems long because my Shub is right next to the terminal.

Signal power level varies with cable length. Altering the cable length will alter the power level at the modem or set top box. This isn't a problem unless the power level is already on the edge of tolerance (whether too high or too low) in which case you get problems.

Network techs deal with power level issues by fitting an attenuator to reduce power or by moving the cable to a higher tap in the street cabinet to increase power. But if they are called out to a power level issue caused by a customer messing with his own wires, the customer gets charged for the call-out.

[AndyCalling]

Originally Posted by jb66

A shorter cable would give you a higher signal than a longer one, your talking marginal differences

I would have thought so too. I would be cutting my cable down because it's really big for the distance (which I realise is very short) and coiled up in the corner though, not to improve my connection. What I want to understand is why a shorter cable leads to a disruption of service.

Could it be that the the system can't drop power levels low enough to avoid flooding the router if the connection is too good? No, that doesn't sound right, but I can't work it out so I now feel that I don't know enough to attempt shortening my cable yet. It would never have occured to me that a shorter cable might cause service disruption, if I hadn't read this thread I might have caused myself no end of grief.

[craigj2k12]

I cut between 5 to 10 metres off mine and the power levels increased by 4db

[AndyCalling]

Originally Posted by craigj2k12

I cut between 5 to 10 metres off mine and the power levels increased by 4db

Blimey, 4db, that's quite a bit really. This cable shortening business is risky stuff.

Thanks loads, Chris, for filling me in here. It would be really great if you could explain why shorter cables cause issues and what the safety limits are. +1 rep to you pal! Oh, you already got 10 gazzillion rep points. Still, surely room for a waffer thin one? ~

Nah, I'm stuffed . I don't actually know the physics of it - just that too high is as bad as too low, which is why excessive shortening of your cable can cause issues just as excessive lengthening can. However, there is a tolerable range so unless it's already on the fringe before you start, it should be ok.

I came across an old schematic for a cable TV system once, the principle of balancing power levels seems to go into the complete design of the system from street cab to all serviced homes, with customers further from the cab being placed on higher taps inside the cabinet, which deliver more power to compensate for the longer cable run.