get the funk out, and give me my POE back

It’s been awhile since I’ve been active here, but as always I end up here seeking real peer produced solutions. Is Jerry still here?

Anyways, annoying problem: Last year I set up some gear on a local tower owner’s site. Simple setup. one 5.2 BH10 and two 5.2 APs
The tower owner has two small huts to locate gear. We put in a switch, battery backup, remote APC power, and W2k3 box, and three POEs. Worked flawlessly!

I share one of the huts with a local FM radio station. The FM is putting out 7KW at 95.6.

At random times, I drop ethernet connectivity to the backhaul. Sometimes so bad the module reboots. Setting the ethernet speed to 10/half definately improves it’s consistancy, but why? My run is only 80 feet. I have replaced the cable. It is shielded… and now grounded on the bottom. I have replaced the POE, and I have replaced the BH10. The results are the same. No reliability via POE. Can someone advise? Will putting RF chokes along the bottom of the ethernet cables help? Should I switch to a midspan POE switch?


When there are FM transmitters near by, I usually have to move canopy down to 10Mbps/FDX from 100Mbps/FDX

10Mbps/FDX isn’t too bad, that’s 10Mbps simultaneous in both directions. It shouldn’t have a hard time maxing out a 14Mbps half duplex radio network!

Anyways, some other gear is much worse near FM transmitters (like Trango where the ethernet ports randomly lock up and you have to reboot the unit all the time) and some gear is better (like the national semiconductor chipsets in Soekris and PCengines boxes) and always works fine at 100mbps near strong FM transmitters.

Try setting the APs to only autoneg 10hdx/10fdx before you do much else.

So the problems I experience with Canopy near FM generally look like the link drops, comes up, drops, etc and also there is significant packet loss pinging the AP itself (5%, 10%, 15%) and both problems typically go away on moving to 10Mbps/FDX.

Apparently there are ethernet lockup bugs in 8.2 (according to the release notes) that are easily triggered at half duplex but not full duplex. So that’s another good reason to keep trying to use fdx even when you go to 10mbit. Whenever you bring up a new link, always make sure both devices are talking either full duplex or half duplex. If one side is not auto-negotiating or forced to full, the other side should auto-negotiate to half duplex. But you will develop significant packet loss trying to run a link half duplex with a device that expects full duplex behavior to be
acceptable (like not transmitting while you are)

whoops, i transposed what i meant to say at the end there. if you are half duplex (on a 4 pair ethernet, this sorta means you freak out if you the other side transmits while you do) then the other device expecting to always be able transmit will in reality just cause errors and dropped packets.


So, yes, I turned things down to 10/full and things are working better. But we still are having short outages. So, how to identify the source fo the problem? It has been suggested to use RF chokes. Has anyone done this before? Results?

wassup Yappa

Try the chokes. I have heard of guys in your situation getting good results.

On the shielded cable, you terminated both ends with shielded connectors - yes?

At only 80 feet my suggestion would be shielded Cat 5 with shielded RJ45 connectors. The shielding terminated to the connectors. Run the Cat 5 inside 1/2 inch EMT conduit, and ground the conduit. Motorola 300ss suppressors are bad about tripping from high power radio transmitters so ditch the supressors unless it feeds customer equipment. You should be able to run 100FDX.

I have an interisting story about cat 5 suppressors that i will put in a separate thread.

Good luck.



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.
Thanks for the feedback guys! Cheers! Good to hear from you fellas!

service is still up, better than ever. I hope it lasts! Thanks for all the tips.