Coax cable - where to buy etc.?
 

I'm trying to find a longer replacement for the coax cable running from wall socket to cable modem. Bearing in mind that I have next to no idea about these cables, can anyone please tell me:

1) Is it just a 'normal' coax cable?
2) What's the proper term for the special screw connectors on each end?
3) Is there anywhere (mail/internet-order in the UK) I can buy the cable from with the connectors already attached?

...and any other advice on replacing it would be more than welcome.

Thanks very much,

SW.

PS. Has anyone just been cheeky and asked NTL to send them a longer cable? Any success?

I get co-ax from somewhere like B&Q and the connectors are in the same dept. (dunno what they're called).
I asked ntl for a longer cable and they sent me one with the origional orders bits and bobs.

If you get a new Argos catalogue they sell a satellite extension kit, it has the right connectors, but will the actual cable be o.k?:confused:

I thought the coax NTL used wasn't the same stuff you'd get in your average DIY store .. I could be wrong

Bifta saidThat's right, without going into too much detail the coax used for satellite is mainly concerned with low loss at a low price.

ntl uses cable that has low loss but more importantly has a higher braid density (Screening). The return path on ntl's network can be subject to ingress by poorly screened cable and badly fitted or inferior connectors.

rg-59 is the stuff isnt it , preferably with crimped not screwed connectors , correct me if i am wrong ;) :) :)

paulyoung666 saidThat's right, but do you realise how many different variants there are of RG59 ?

Not all RG59 is double screened, there are many versions and I can only remember the BU and HE versions off the top of my head.
There are many cheap cables sold as RG59, I have seen some very poor RG59 with poor braid density and have failed to get specfications from the manufacturer/supplier.

Thanks for the advice, everyone. I've found a potential supplier of RG-59 (B/U variety):

http://www.homestead.co.uk/cx59.htm

I believe 75 ohms is the correct impedance... Does this look like it'll do the business?

if you extend it you can have loses that might have on effect on the use of the service. it is a balanced lenght of coax

Aye, point taken; if it turns out to be a problem, I'll have to reverse it. I'm planning to extend the coax run from the current 1m to a total of 3m; do you think that'll make a significant difference to speed?

Just dont think of using the cheap stuff that you see on the markets, where the seller assures you that its fine for what you want.
Its usually poorly screened cr@p.

Nah, my installation is > 10m with a perfect connection.

Sam Williams, i have about 20 metres of TFC T10 cable (see image below)

http://ebay3.ipixmedia.com/abc/M28/_...e04dd8/i-1.JPG

It works fine with cable modems, cable tv, satellite tv etc. How much do you need? If you're interested i can send you some - no charge.

not sure of the loses for that cable it depends what your SNR and power are at the moment if it stays within limits should not be a problem at the most its probably a couple of db difference

cable atten here

according to the table about .3db should not worry about that

just a point if NTL used RG11 they could use less power

Ezenden, thanks very much! 2m would be great - 3m would be even better. Let me know about postage etc. via PM?

Sam, just PM me your address and i'll post it this afternoon. I'll send you 3m, dont worry about postage.

Thanks mate! Will do.

The connectors are F-Type plugs. Maplin sell them.

The cable on my installation is CT100, which is double screened and has half the loss of RG59.

dellwear well spotted! As you say, don't know how good the cable is, but maybe worth a try for anyone else who wants to extend their cable. Comes with a coupler as well...and if it doesn't work, then back to Argos.

Sam, its sent.

RG 59 is no longer used by a majority of the franchises. The signal loss is just to great. it was ok for the old analogue system but due to the digital signals being transmitted 20 db down on the analogue. this type of cable was only used externally from the omni box to the internal isolator and from the isolator to the CM/STB.

Signal loss 3dB per 100m at 10MHz

RG 6 this size cable is now the norm for internal and external cabling and on a majority of installations is used as the drop cable up to 130 metres.

Signal loss 2.3dB/100m at 10MHz

RG 7 used for runs between 130m to 180m

Signal loss 1.9dB/100m at 10MHz

RG 11, used for runs of 180m and upwards

Signal loss 1.2dB/100m at 10MHz

Higher frequencies will attenuate greater than lower frequencies so we usually take signal readings in the higher bandwidth area where the analogue and digital signals are being transmitted so lets say at 643MHz on a RG 6 you will get a 1.5 db drop for every 10 metres of cable on a RG 11 cable at the same frequency you will get a 0.95 db drop in every 10 metres of cable.

But it doesnââ‚ƚ¬Ã¢â€žÂ¢t stop there we aim for a signal level of 0 db at the omni box if you have one stb and one cable modem youââ‚Âà ‚¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢ll have a two way splitter in the omni box which will cause a signal loss of -3.5db per port on the splitter and a three way splitter youââ‚Âà ‚¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢ll lose -6.5 db per port. With the advent of digital and the digital signal levels being transmitted 20 db down on the analogue this has presented us with quiet a few problems and is one of the reasons why some customers will have experienced service call after service call, but we now have a fix for this problem by using a HDU ( home distribution unit ) which in all tense and purposes is a no loss 4 way signal splitter.

Your optimum signal level for a cable modem is -4 db at 402.75mhz some areas may vary. donââ‚Âà ‚¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢t worry if itââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s a few db up on this lets say -1 db , but if your getting lets say + 3 db this may start to cause a problem with noise and packet loss. On the other side of -4 db your Signal can drop down to -12 db without any significant problems. you can check this by looking at your diagnostic screen http://192.168.100.1/ username: root password: root if you have a Surfboard or an Ambit.

Your optimum levels for your stb at 643 Mhz -5 db we usually take two different readings one on a low frequency and one on a high, we like to see all the signals between 419Mhz to 747Mhz as flat or linear for a bit of perfection, but it is not a problem if we see a bit of a positive slope between these two figures and as long as itâ₠¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s not greater than 7b.

As for connectors ( F type connector) please do not use the sky type twist on they are absolutely rubbish for use with cable. We used to use a crimp type of connector ( Gilbert connector ) but we found this to be a inferior type of connector and prone to let in ingress. We now use a f type connector called a snap and seal that is air tight, the tools you need for a snap and seal are quiet expensive and q

That's interesting. Is that an analogue or digital level at the omni? (on the Langley platform, the digital signal is 10dB down on the analogue, not 20 btw, well it is in our franchise at least) We design the network to a minimum of +11dBmV at the Omni, but that is an analogue level at the top of the band. So, if you're aiming for 0dBmV (digital) then that would tie in.

Augat Snap-n-Seal connectors + assembly tool:
http://custom1.farnell.com/cpc/searc...eyword=cn03810
(or, at a push, use a Workmate, a sacraficial 'F' coupler and a lump hammer) ;)

Belden 1505A (RG59/U)
http://custom1.farnell.com/cpc/searc...eyword=cb01736

Belden 9248 (RG6/U)
http://custom1.farnell.com/cpc/searc...eyword=cb01735

Belden 8213 (RG11/U)
http://custom1.farnell.com/cpc/searc...eyword=cb01737