I wanted to add an option to control a Micro Sawppy Rover using classic radio control equipment, but I didn’t have a matching receiver for my Spektrum DX6i transmitter. I have a Spektrum DX3E transmitter with a corresponding SR300 receiver, so I tried that next.
I tried to bind the SR300 receiver to my DX6i transmitter, but they didn’t want to work together. The DX6i is an aircraft transmitter, the DX6E is a ground vehicle transmitter, so its corresponding SR300 receiver only talks to Spektrum ground transmitters. In an older generation of controllers, the two worlds were on entirely different frequency bands. In the USA, 72 MHz is reserved for aircraft and 75 MHz is reserved for surface vehicles. The newer generation of technology in DX6i and DX3E work on the 2.4GHz band so I had hoped they can interoperate, but apparently not.
I’ve found references to how ground radio didn’t have to accommodate as many simultaneous users, because they tend to be in a small area. Plus they also need to be very responsive, since vehicles in a competitive environment are running at high speeds while only a few centimeters from barriers and each other. In contrast aircraft don’t usually fly in as tight of a formation, but they need to accommodate more simultaneous users because they operate in larger arenas. Compounded by the fact an aircraft “hears” a much larger area when it’s up in the air versus a vehicle on the ground. I don’t know how such tradeoffs manifest itself in the actual radio transmission protocol. It doesn’t really matter if there’s a technical reason anyway, because it’s apparent Spektrum has segmented the two markets.
I wanted to use the DX6i because it had more channels of control, but the DX3E will suffice for Micro Sawppy because two channels (one for steering, and one for speed) is all I needed to start.