Does anyone know what frequencies / range is used to communicate with the mavic?

I spread spectrum utilized ?

No data on the DJI page about that.

Not sure what you mean, but for the drone and RC's frequency, we have the introduction about it on our official web:

occusync with the controller uses 2.4000Ghz - 2.4835Ghz.  occusync constantly jumping frequencies depending on conditions to avoid interference and it can even reduce its bandwidth from 20Mhz (full width) to 10Mhz (half width) to improve range and be more resistant against signal loss..

without the controller and using wifi with phone to the mavic pro it does typical dual band 2.4Ghz and 5.8Ghz 802.11ac wifi with software enforced range limit to around 350 feet max without the RC.

ImHereToCrash Posted at 2017-8-31 20:55
occusync with the controller uses 2.4000Ghz - 2.4835Ghz.  occusync constantly jumping frequencies depending on conditions to avoid interference and it can even reduce its bandwidth from 20Mhz (full width) to 10Mhz (half width) to improve range and be more resistant against signal loss..

without the controller and using wifi with phone to the mavic pro it does typical dual band 2.4Ghz and 5.8Ghz 802.11ac wifi with software enforced range limit to around 350 feet max without the RC.

Thanks for the good information guys, this is what I was looking for as I'm a wireless guy as well.