Single conversion receivers have a single local oscillator circuit for demodulation. Dual conversion revceivers have a second circuit for greater image and interference rejection.
BEC stands for Battery Eliminator Circuit. It takes 7.2v-8.4v commonly used for electric RC and regulates it to 5.0v which allows the receiver to operate properly without the need for a separate battery pack.
After hard landings or crashes the receivers ceramic filter or tuning coil(s) can become vibration sensitive. Other sources of interference can be RF noise generated by bad bearings in the engine, electronic ignition systems, loose screws, or other metal to metal contact in your R/C application.
