I have resolved the compatibility problem of the "SPM1001 DSM 3-Channel Series Surface System: R-1" with jr x-756 2 stick version radio. I have placed an electrolitic capacitor of 470 uF between contact that carry PPM signal and 1 Kohm resistor of PPM pin on PCB of jr-x756 radio, where RF module is placed. The capacitor reduce noise in moment of radio startup. This is a high pass filter, it filters the dc component from microprocessor.
Actually i'm using spektrum module on jr x-756 radio.