Hey folks,
We are colocated with an FM radio station and have lot’s of problems communicating via POE to our RB112s and 532s (from server in radio hut up the tower to the POE(about 25% loss), 80 ft shielded CAT5E. We think it is due to the 10000watt amp sitting in the same room for the FM radio. We are considering a POE midspan switch. Any recommendations? has anyone had this problem before? what can I do to reduce noise? wireless signals are great=-60dbi, CCQ 90%
Perhaps ground exactly one end of the shielded cable, so that it shields but does not carry a current. Use a metal outdoor case indoors for your equipment? We have no problems with non-MT gear at a radio station mountaintop site we are at. We have an HP managed switch and alvarion radio equipment (which uses POE) there. No problems at all.
I grounded the CAT5E shield yesterday per your suggestion. Seems to be a little better, but we still dropped last night. The tower owner says “harmonics!” and suggested moving gear around and changing the length of the ethernet cables. Didn’t make much sense to me. He also suggested throwing on RF chokes on the ethernet cable. Has anyone done this before???
DesertG8,
RF Chokes are made out of a material called Ferrite and are either purchased as units which clip over the cable or can be obtained as rings in various diameters. The ring type is often more useful as you thread the cable through and wrap around a number times, so you can experiment with how many turns of cable you need to counteract the RF interference. Different frequencies need a different number of turns, effectively you are creating a tuned circuit which is selectively attenuating the stray RF.
I used to work for British Telecom and 20 odd years ago when digital phone systems first started to be installed, we had a lot of problems with stray RF interference, often from radio systems operated by taxi (cab) companies. We solved most problems by wrapping 4 or 5 turns of the phone line cord through a Ferrite ring. Place rings as close to the equipment as possible at both ends of the cable.
If you’re using shielded Ethernet cable you may want to try providing your own grounding spike. If you’re using the same ground as the source of the RF interference you may just be adding to your problems.
Hello,
Update:
Purchased all the clip on and ring RF chokes our local radio shack had. I installed all of them, not really knowing what I was doing. On the most problematic cables I used 4 loops on the top and bottom of the cable. I also moved the ground to an independant ground. WHOA! That helped alot! Even more than the chokes. I also moved our rack into a corner of the hut, coiled the power cables, and placed 4X2 steel sheet between my switch and the FM radio gear. I also installed the doors to the rack for the FM radio and closed it.
In any case, everything seems to running well. It has been five hours with no drops. I’ll post results after 24hrs, as I am still skeptical. I have a question regarding weather it is better to ground a shielded cable and use rugular ends, or use the shielded ends with no grounding. I’ll start a new post with that.
Thanks for the feedback guys! Cheers!