FM-Proof Routerboard

Hardware MikroTik hardware general
1

Hi! We have a site (Just installed) co-located to 2 FM stations, and unfortunatelly we can’t move away.

We are using an rb750 as a switch (L2), and off course it’s not the model with the best EMI shielding, but that’s what we had in hands.

Ethernets didn’t appreciate the radio stations, tough.


What is the most EMI resistant board i could try on that site?

All cables are shielded, off course.


Every help appreciated!

2

Put it in metal box and ground it.

3

Everything is already in a steel waterproof box.

The longest cable run is about 3M. Shielded cable everywhere.

The pole is made of steel, and is grounded aswell.

The weak link looks really to be the rb750 (Not even shielded jacks), the input protection circuitry was not loaded (vs rb750UP). It uses the same processor as Ubnt’s M stuff (Not famous for ethernet rugedness).

Unfortunatelly it was the 5 port switch we had in hands. I am asking to see if someone already field-proven a board to be more resistant to 100mhz interference.

4

Do you use kit power supply or PoE-injector? I think you can try to ground minus (-) of power jack or ground Routerboard directly (http://wiki.mikrotik.com/wiki/Manual:Grounding). I don’t sure minus is grounded on the board, maybe some one should confirm that, or just check it with tester.

5

Ferrite beads on the ethernet? I have heard that people have luck on FM towers by putting the ethernet cable in metal conduit.

The RB450 appears to have shielded ports.

I doubt the CPU model has much to do with it. Grounding and shielding of the ethernet ports are likely much more important.

6

We have like 50 FM towers in use …

  • Keep some distance from the FM antenna’s ! (this is the most important 3 meters is the minimum)
  • Use outdoor shielded cable with shielded connectors
    (ubnt has tough cable PRO with special shielded connectors)
  • use ferrites (we had a situation with a 3KW station where the ferrites melted in to the cable)
  • use a metal box, and a shielded board (RB493?)
  • keep cables away from the FM cables , no loops in cables
  • do not use cheap POE inserters , if its a 100 mbit routerboard you can put power directly to the ethernet ports using a soldering irion.
7

I`m going to run the ethernet cables into steel tubes, and try to star-ground everything to a point in the box (wich is in the pole. there is no ethernet cables longer than 3m.).

Still, what RB has the most resilient ethernet ports?

rb333 looks promising, as ethernets are individually handled, EMI from all cables should not mux in a single controller.
Problem is we need all 5 ports..

Cat7 may be a solution, but is very hard to find.

I tried to make a drawing of the situation. Anyway, my point is, which routerboard is better suited for an high-rf environment?
fm.PNG