Rodney

Positive shift and negative shift work equally well. Positive shift just means that the transmitted RF frequency is shifted upward when modulated with a data pulse and negative shift means the data pulse decreases the transmitted RF frequency. This excursion is usually about 5 kilohertz from the nominal frequency. While most people call the modulation technique used by RCers FM, it is really frequency shift keying. True FM varies the modulation frequency somewhat linearly while RCers do it in a single step frequency shift, thus frequency shift keying. Dual conversion and single conversion is not related in any way to the transmitter. Dual conversion is when the incoming signal to the receiver is converted to a second frequency, usually 11 megahertz. This signal is conditioned and then mixed again with a second frequency with a resultant frequency of usually 455 Kilohertz. This signal is then conditioned and converted to a series of pulses which continue on into the decoder chip in the receiver. Single conversion receivers omit the 11 mhz stage, going directly to the 455 khz stage. This makes them more apt to be interfered with by third order harmonic distortion and somewhat more suceptable to other interference. We RCers are quite blessed with very good equipment now. Any of the major brands perform admirably.