Radio compatibility

From Combat Robot

It's possible to 'mix and match' R/C radio components from different manufacturers, but there are a few things you need to know.

Shift

Different brands of R/C transmitter all send a similar pulsed signal to the receiver, but some manufacturers send those pulses as 'peaks' and some send them as 'dips'. These are referred to as positive and negative shift. Futaba and Hitec are negative shift, while Airtronics and JR are positive shift. Some receivers are 'universal shift' and can correctly interpret either type of peak format. Make sure the receiver you plan to use can sort out the signal your transmitter is sending.

Frequency Crystals

R/C receivers come in two basic designs: single conversion and double conversion. Double conversion receivers are less prone to interference, but either type can receive the same signal. You can find details on the differences at the R/C Radio FAQ.

The compatibility issue is with the frequency crystals -- single and dual conversion receiver crystals are not interchangeable. Manufacturers color code the receiver crystal tags to identify single versus dual conversion crystals. Some receivers require special 'short' crystals as well. Crystals are not generally interchangeable between brands. AM and FM crystals also do not interchange.

Receiver Plugs and Wire Colors

The receiver outputs for all manufacturers are three wire plugs. The wires carry + and - DC power at the same voltage supplied to the receiver, and a position signal. The power and signal format is compatible between all brands, but the wire colors differ between manufacturers.

	Power -	Power +	Signal
Futaba	Black	Red	White
Hitec	Black	Red	Yellow
JR	Brown	Red	Orange
Airtronics	Black	Red	Black or White

Warning: some Airtronics servos and receivers have the wires in an incompatible order -- power polarity is reversed. You must re-order the plug pins in these before plugging them into components from other manufacturers. Failure to do so will destroy components!