Hi I have Sanwa Airtronics Mx-3 75mhz that currently has channel 71 in it. I wanted to use the same remote for another car so I purchased Futaba R303 synthesizer receiver. After i dialed in channel 71 there is no response. I thought futaba and airtronics equipment isnt compatable so I tried 75mhz Futaba R123F RX and put in the channel 71 crystals and it certainly works. Is there any explanation what the futaba synthesizer receiver doesnt work with the MX3 transmitter?

I know the synthesizer does work as i tested it with another 75mhz futaba mj transmitter with channel 66. The unusual thing here is that when I put channel 66 crystals in the Mx3 nothing works

Any info would be great! Thanks