Elad:

I was just keeping the "Front" name in front. And we're both "Nacirema" people, so what the heck.

Pulse Position Modulation and Pulse Code Modulation are just two different ways of encoding the informatrion sent by the transmitter, as you supposed. And being technical, neither can properly be called "Frequency Modulation" since no modulation is done - the correct term is "Frequency Shift Keying." That brings us to another misunderstood term: "Shift." You will hear "Negative Shift" and "Positive Shift." This refers to the frequency shift being to a higher or lower frequency. Not to worry about if you keep the same brand tx and rx, or be sure to get the correct version of a different brand. Some rigs will let you select positive or negative shift, and coming on the market now are rx circuits that will work with both shifts.

Back to the PPM and PCM. The PPM has a constant stream giving each channel information in a serial format, while the PCM encodes all channels in a digital word, effectively giving a much higher data rate. In addition, if the PCM rx gets a corrupted word it will ignore it, and can be set to several different actions in case it loses the data stream. This is referred to as "Fail Safe," but that's so much bs. There is no such thing as total loss of control being safe. Set it to neutralize the controls and chop the throttle, then if you get your tx back on the air you might save it, but at least the plane wont go in at full speed.

And finally, PCM makes your rx cost two to three times as much as a PPM rx. Everytrhing else is the same.

Bill.