Multiple Antennas on One Pole

Q: Do you have an opinion of physical separation when one mounts multiple radio units on the same pole?

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It generally depends on frequency separation and antenna design.

 

Frequency separation: when the operating bands are significantly different (e.g. 5Ghz and 2.4Ghz), the physical separation is less important.

 

Antenna Design: a solid reflector dish antenna with narrow beamwidth of 2-3 degrees is less susceptible to problems than a panel antenna with beamwidth of 30 degrees.

 

As a general rule, we recommend at least 1m and more than 3m if possible.  (at 2.4GHz, attenuation of the signal in air over 1m is already -40dB, and 3m is about -50dB)

 

Typically, interference problems from antenna proximity are caused by cable and connector leakage rather than the antennas themselves.  I am aware of several cases where leakage between pigtail cables has caused some significant interference problems on links. 

 

The other thing that is important is what is at the REMOTE end – if you have two links running in parallel, for example, then there is virtually impossible to physically separate the two antennas in a way that will prevent one device at the remote end from receiving signals from both transmitters.  In those cases, it is best to make the channel separation as much as possible (i.e. 5.8 vs. 5.4 GHz)

If you have any further questions about this topic or any other, feel free to ask!