Frequency spread to avoid interference?

I have four PMP 320 APs, how far apart should I space the center frequencies if the bandwidth is 10mhz?

I was thinking of this:
AP 1 - 3.60Ghz
AP 2 - 3.62Ghz
AP 3 - 3.64Ghz
AP 4 - 3.66Ghz

Presuming you’re USA based, you can only currently utilize frequencies where the entire band lies between 3.650 and 3.675.

Meaning that with 10mhz width (as we are also using) you can only manage two non-overlapping channels, like 3.655 and 3.667. (the first would then cover from 3.650 to 3.660, the second from 3.662 to 3.672)

Keep in mind that when you set the freq, you’re setting the center of the band, and FCC might not look too kindly on you overflowing the designated range of 3.650-3.675…

The upper half of the band, 3.675-3.700, is supposed to become available in the near future, IIRC. In the meantime you’ll have to deploy an ABAB pattern around a tower for a full circle of four APs.