AP Cluster on FM Tower


have Anyone installed set of 2.4 ap+cmm+bh on FM tower?

the fm power is around 1500watt.

We recently installed the cluster on the tower, and almost everyday got “weird” problems. and each time the problems is appear and dissapear without exact answer. Most problem is the unexplainable "RTO"

sometime the backhaul is not working at all, but the 4 AP is working but there are lots of RTO, after restart or doing physic “default” from cmmicro everything is running again, Ping between AP within CMMicro is rto, when we touched the stp cable head at cmmicro than the ping look nice again.

any thought?

we are thinking to move the cluster apart 30-40m from the FM omni/yagi.



We installed a 2.4Omni and several BH’s on a FM Tower. This Tower is also home to a Bell Canada Cell broadcast, most of the Provinical Police use it for communications as well. There is also other paging equipment on it, another WISP and a Backhauling system for the municipality.

We didn’t have any problems UNTIL we tried to install a BH at the same height as the Radio Stations antenna. When we installed the BH we couldn’t even ping it. It just wouldn’t work. We moved it down a few feet and it still didn’t work. We ended up having to move it 25ft down the tower in order to get it to work.

Once we got it to work we moved up 1 foot and it stoped working again. Move it back down a foot and it’s fine. The FM broadcast just must have been over powering the radio and basicly shutting it off.

But all the links are up and running fine as well as the AP. Just had to stay well below the FM broadcast.

Verticle seperation will help the situation. Also, be sure your using shielded Ethernet, grounded end-to-end.

We just recently installed a 900 MHz cluster, 2.4 Cluster, and 5.7 GHz backhauls on a 400 Ft tower. We’re colocated with an FM broadcaster who is pumping out 4500 Watts. We’re about 35 Ft from the FM Yagi’s.

The first problem we had was we couldn’t get a GPS link, until we walked about 100 Ft away from the tower. No satellites would even register.
Then we noticed ethernet traffic would work with some but not all of the AP’s.

We were able to find a sweet spot on the tower where GPS seemed to work OK, we installed a 35’ beam and mounted the GPS antenna about 25 ft from the tower. This helped GPS reception tremendously. We are now receiving sync to all 8 sats.

We forced the AP’s to 10 Mb/half duplex and for the most part traffic was working. I didn’t see any errors on the radios, but I really didn’t want to risk it. Everything pointed to interference.

We were already using shielded cable, however, it wasn’t the foil shielded stuff that motorola has recommended. We had been using some heavy aluminum shielded, silicon filled Cat5E cable that was supposed to be even better. The cable has a seperate copper 24 gauge strand that is supposed to act as a ground, connecting your shielded ends together. The problem is that the cable is two thick to completely enter the AP or the CMM. We trim off the aluminum shield and just leave the plastic wrap 6 inches from each end.

Since we experienced the problem, I decided to try motorola’s recommendation, even though the cable was expensive. We really wanted to get the tower going. We ordered the Canopy cables from Best-Tronics.

Well long story short, we replaced the ethernet cables with the new ones, and everything lit up. The tower has been up for 60 days now, we have 35 customers on it. Everything seems to be going OK.

The only thing I can recommend, is stay as far away from the FM feed lines as possible. We mounted to the opposite leg on the tower. We happened to have a spectrum isolater, and boy where those feed lines putting out a lot of noise.

we have had mixed results on some FM we are running fine on others we got problems.

A common one was, we would loose etherenet (cat 5) connectivity to the units.

Vertical seperation helps

This community is ROCKS !! :smiley:

Today, Ill try to move down the cluster 20m from the FM Yagi, and wrap all the stp with additional allumunium foil, also wrap the CMMicro as well and the gps cable too.

wish me luck