2.4Ghz and 5GHz antenna spacing

Unanswered Question
May 16th, 2009

We are creating a vehicle as sort of a communications center on wheels. It has satellite, HF, VHF, UHF, and Amateur radios on board, and lots of antennas on top. I have a mast for the Wi-Fi bits, and I am wondering if the mounting shown in the attached picture is acceptable? I know that you should not mount two 2.4GHz antennas this closely (when they are controlled by two different APs, even on different channels). What about the pictured scenario where one antenna is 2.4GHz, and the other is 5GHz (Both are connected to the same AP)?

Also - these antennas are within 4 to 8 feet of the antennas for all the equipment listed above. What sort of problems are we likely to experience?

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scottmac Sun, 05/17/2009 - 05:55

Interesting setup. In my opinion they should be given wider physical separation to prevent front-end overload.

It doesn't matter that they are connected to the same AP, they are still different, separate radios. If anything, that would suggest that you should give antenna cable length preference to the 5GHz radio, since it will have the most cable loss.

More separation is usually better, but as a minimum, I'd give it at least five wavelengths. If you have some can/notch filters I'd use 'em, but you'll probably also need to boost the signal.

Also note that the 2.4 and 5GHz signals can be harmonically related at several nodes, depending one the channels used.

As always, a "site survey" would be your best path forward. Since you know what your goals are for this setup, put the antennas on a stand or short tripod and move them around in the acceptable mounting areas and do a little walking around to see if the coverage is what you need.

Good Luck

Scott

Robert.N.Barrett_2 Sun, 05/17/2009 - 09:30

Thanks, Scott.

A friend pointed out the obvious to me after I made this post. The antennas are about the same distance apart as they are when you mount the rubber-duck stubbies directly to a 1242. This should not be a problem.

Site Survey / Testing is definitely the route to take to ensure there are no problems.

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