I came across a range of frequencies from microhard 400Mhz-2.4GHz. Now the commonly used radio is their p900 for pixhawk hardwarwe. I wonder if it is possible to use other radios from them like p400 p2400 etc?
My experience is that Microhard radios are autopilot/telemetry agnostic, what I mean with that is as long as the microhard radio has a serial port or ethernet to interface with the pixhawk it does not care if it is mavlink or some other telemetry protocol.
Depending on the Microhard radio it probably has a serial port that could connect directly to the pixhawk hardware (might need some rs232 to ttl converter).
put a companion computer over serial to the pixhawk (such as a raspberry pi running mavlink-router) then connect the microhard over ethernet to the companion computer.
The frequency of the microhard does not matter in regards to pixhawk or mavlink, it’s more interface options to the pixhawk.
I use the microhard pmddl2450 and the pmddl900 as well as 1.8ghz version with pixhawk hardware, please note these are all digital radios compared to the analog p900 but the above statement still complies to the p900 or p400 radios.