Originally I used a three channel R/C system. I kept the transmitter on all the time. Like you all suggested I could have used its outputs to trigger the PIC's PWM signals.

To take R/C control I tuned on channel 3. The receiver signaled the PIC that channel 3 was active. The PIC flipped the DPDT relay thereby steering the radio receiver's servo signals to the car.

This was not a good system because the model level car which is the basis of my work comes naturally with a 2 channel R/C. Adding the third channel was a big expense. Too much for our school systems.

Ken