Splitter-router distance?

[Timothy Murphy]

How long can the cable joining an ADSL splitter to a router be? Is there a greatest recommended distance?

[TMC]

Regards

[Dave Liquorice]

How long is a piece of string?

Within the relatively electricaly noisey enviroment of a home as short as possible. Have a google, there is plenty of information out there, but essentially, use twisted pair cable and disconnect the bell wire and earth wires.

[Andy Burns]

It's not ethernet at that point, so it could be thousands of feet (it's already likely to be that long from the exchange to the splitter), but the longer it is the slower the ADSL will be.

[dennis]

You don't actually need a splitter if its only ADSL so it can be as long as the telephone line, say 6 miles.

You do need a splitter if you have telephones, etc. on the same line and the cable can be just as long if the cable is as good as the telephone cable.

[Timothy Murphy]

The reason I ask is that I have a choice between attaching the modem/router by a very short (1 metre) cable to the splitter/microfilter at the point where the telephone connection enters the house, or having the modem/router 10 metres away, where it can be attached to a UPS.

I should admit here that I am talking about a setup in Italy, where there are fairly frequent thunderstorms during which the electricity supply often goes off for a second or so.

I recall some years ago that my sister-in-law's ADSL connection in Manchester was causing endless trouble, and I seemed to cure it by making all the connections as short as possible. But this may have been a coincidence. (I think the TalkTalk expert recommended shortening the connection.)

[Steve Firth]

Well no, you won't be using cat5 from the router to the ADSL splitter will you?

[Steve Firth]

I'd have it close to the master socket. A UPS is only really supposed to give you time to shut down the system(s), not to keep on working. The benefit of greater speed and reliability outweighs the ability to run on a UPS.

There are small, cheap UPS bricks intended to run a router or switch during a power failure. I'd get one of those if it's an issue for you.

Tell me about it.

I'm surprised that you can get DSL. All that TIM offer is ISDN where we are. I rely on 3g for network access using TIM's 100 euro for 12 month's Internet bundle.

[Owain]

as close to the telephone connection as possible.

If the router is powered by a plug-top power supply then you could extend the (extra)low voltage power cable from it to the UPS

Owain

[Tim Watts]

+1. The quoted cat 5 length limit applies to ethernet only.

as the filtered ADSL signal is the same as what's coming down the phone line, minus the DC and low frequency audio parts, you could have several miles if you wanted, with the ensuing degradation of ADSL speed.

Cat 5 is a prefectly reasonable choice of cabel to use as long as you choose to use one pair and not 2 wires from different pairs.

Cheers,

Tim

[John Rumm]

Short phone line, long ethernet is the best solution usually. If you want to run it from a UPS, have you considered using a power over ethernet injector to carry power from the UPS protected supply to the router via its network lead? If the router does not support PoE, then you can get a PoE extractor to go on the far end of the cable.

[Toby]

You might - CAT5 would not be an unreasonable choice of cable to carry a telephone line to an ADSL router.

[TMC]

so that will teach me to read the original post properly

brain is fuddled with cement mixing etc

Regards

[Dave Liquorice]

Except if the ADSL modem keeps turning on and off any automagics associated with the line speed are likely to knock it right back and you'll just have to wait for them to decide that the line can run as fast as it has synchronised at. That's assuming that the interference from the lightning hasn't already done that. If I detect a thunderstorm withing half a dozen miles of her I switch the ADSL off until the storm has passed in order to preserve the BRAS rate.

Assuming that italian ADSL works like BT ADSL...

[Andrew Gabriel]

10 metres is fine. Use either a twisted pair on Cat 5 cable, or phone cable which is twisted (like permanent phone wiring). Try to avoid a long untwisted extension cable.

As someone else said, the modem doesn't need a filter - you can connect it directly to the line. It's only the phones which need filters, and the modem socket on them is just a convenience.

I probably have something like 20m of Cat 5 between the master socket and the modem. I did try moving the modem to the master socket, but it didn't make a scrap of difference to the S/N ratio, or the sync speed, so I moved it back.

Well, you don't want unnecessarily long lengths. But it could simply be that you fixed some poor quality cables/terminations in the process.

[Dave Liquorice]

Might be able to, depends on the current draw of the router. If it's pulling a couple of amps at 5v the volt drop on 10m of ordinary "bell wire" type DC cable is likely to be too high and the device won't be happy or work at all.

[Timothy Murphy]

I've seen a ?40 UPS (Trust brand) in a computer store just near me, and am thinking of getting that. It says it will keep a computer going for 8 minutes.

But it would probably be best if the UPS just allowed the computer to close down properly (as you suggest). I'm not sure if this is a function of the UPS, or if the computer has to be told in some way to close down?

Thanks for all the responses, by the way. I've decided to put the modem/router (Billion brand) by the telephone inlet, and connect it by ethernet to the computer. The ethernet will have to go outside the house briefly.

The modem/router seems to have survived going on and off several times; it is the computer that seems to get confused. I think it is probably when the power comes on again while it is still trying to shut down.

[Andrew Gabriel]

I pull this trick with many small devices, to power them from the PC, remotely over the Cat 5 cabling.

Most modern switches, WiFi access points, ADSL modems, etc run internally from about 3V. They contain a switched mode PSU to transform the wall wart's 6 - 12V down to 3V. This means you can often run the 6 - 12V over long lengths of cable losing some volts, and the item will still work correctly. The switched mode PSU inside will draw more current to compensate, and keep the power consumption of the device roughly constant (although you'll lose additional power in the long cable).

I routinely do this with things like wireless access points, as a kind of poor man's Power over Ethernet. If the device is 100Mbit ethernet, I use the two spare pairs in the cat5 for power. I've made up some adaptors for this purpose.

It also enables me to power these devices directly from the PC's internal power rails and dispense with the wall warts completely (but do include a fuse so you can't draw 10A over your Cat 5 if something goes wrong - I use PTC semiconductor fuses for this).

Also, this is only suitable for items with all isolated connections, such as twisted pair ethernet, and all ADSL ports I've checked on modems (although I can't confirm this applies to all ADSL modems). Don't try it with any device which has non-isolated connections to anywhere else.

[Steve Firth]

I've had variable result with Trust products but given the application you may get away with it

A good UPS such as APC can be connected via USB or network to your PC. When there is a power out the supplied software can schedule a shutdown before the battery goes flat.

[Dave Liquorice]

There is a serial or USB connection between the UPS and the computer and a bit of software that sits as a service listening to the UPS. When the power goes off the UPS signals the PC and it shuts down. There may be a pop up and a configurable delay to enable you to save stuff properly first.

Rapid power cycles aren't good for kit but the trouble with an ADSL modem doing it several times is that it can really knock back your speed for several days. I've had my normal 4.5 to 5Mbps bashed down to 1Mbps by a thunderstorm and that's without power cycling.