O.T. Modem Distance

Looking for some off topic help here....

I have a customer, who has a modem for auto-metering some tanks about 500 feet across a parking lot. The company that supplies the gas, used a CAT5 cable, and is having problems. They haven't been able to get it to work, and he asked me, to get some direct burial telephone cable to use. The cable is in PVC, but being across a parking lot, the integrity of the PVC is in question.

So I found some 22/2 dir. burial phone cable, but I've never had to spec for a telephone type modem before, and don't know if this will be the solution, or if I will still have problems. I was suprised, that I had trouble searching for this on the net.


Thanks for your help,

brian

cat 5 cable is only good for 300 feet Cat 5E/cat6 can carry to 1000 ft
phone line for a modem is usually good up to 1000ft if memory serves me correctly however I've found that the modems based on phone lines are more prone to fail due to EMF. PVC will rot underground. however the underground phone cable is in a rigid rubber coating as far as I remember yuo have to bury it a minimum of 3 ft but that will depend on your electrical code for you area

Here in the UK, all direct buried telecoms cable is filled with petroleum jelly to protect the inner cores.

PVC will rot eventually, but it depends on the soil. If you are going to have to dig the ground anyway, why not install in ducting, at least then if you get another failure, cable replacement should be easy.

Jon.

Thanks,

The PVC is already laid, and hopefully not rotted or caved in yet, for re-pulling wire. I didn't do any trouble shooting or anything for what is there, just knew that for 100 Mb ethernet, the max distance for CAT5 was 100 Meters, and wasn't sure if it was different for a modem signal vs ethernet. Customer just told me, to pull telephone wire.... and I wanted to make sure, that it should work, before I do it. The only telephone modems I've hooked up, are plugged into the wall, and I never worried about distance, as I have with other networks.

thanks,

brian

mordred said:

cat 5 cable is only good for 300 feet Cat 5E/cat6 can carry to 1000 ft
phone line for a modem is usually good up to 1000ft if memory serves me correctly however I've found that the modems based on phone lines are more prone to fail due to EMF. PVC will rot underground. however the underground phone cable is in a rigid rubber coating as far as I remember yuo have to bury it a minimum of 3 ft but that will depend on your electrical code for you area

Click to expand...

I think that cat5 cable is only rated to 300 feet IF you are trying to run ethernet comms over it. It has to do with signal propagation times and the amount of time ethernet adapters wait to listen for a collision on the line. Cat5 should be able to be used for analog phone modems at a longer distance than 300 feet. It is actually better cable than standard telephone wire.

I would suspect that the OP is having trouble due to improperly rated wire (indoor only wire installed underground), pinout problems, ground loop/difference in ground potential problems, or damaged cable. I would NOT suspect that the link is failing because they used Cat5 cable for a 500 foot link.

Brian

edit: If they are asking specifically for telephone grade wire, you could spec underground rated Cat3. It was an upgrade to standard telephone wiring in that it was twisted pair where standard bell wire was not necessarily twisted. It would support upto 10MB ethernet comms, although that is not needed. It is NOT any better than Cat5 though.

I would test the existing cable. If you have two good wires, you could go RS485. If the PVC Conduit is in question, maybe go wireless to save your parking lot.

http://www.data-linc.com/ddaa/index.htm

What is the Auto-Metering monitoring? What are the signals, discrete or analog?

Thanks,
Joe_WaZoo

How about wireless? I have several Prosoft ethernet radios in service now. I dont have any broken wire problems.

Brian,

Look for some #18 Cat 5E or Category 6 phone cable to pull in the existing conduit. Signal loss is also dependant on the impedance of the cable, and the larger wire will have smaller losses as well as more mechanical strength. I have had problems using #22 phone cables in areas that are subject to small vibrations. The wires seem to break internally after several years, even though the insulation is intact. I am not sure if it was actually vibration (this was a phone line underground and up the wall of a building that had an overhead crane) or some type of electrical voltage surge, but larger diameter wire (smaller gage) solved the problem --so far anyway.