Without getting too technical, a single conversion receiver means that the received signal is converted from one frequency to another frequency which is easier to work with. A dual conversion receiver just means that there are two 'steps' to that frequency conversion, primarily because it can get rid of some things that just aren't needed/wanted in that 'extra' step. If the signal is strong enough in relation to all the other signals present, a single conversion receiver will work just as well as a dual conversion. That usually means that it's very slightly more prone to interference than the dual conversion, but in most cases, it just isn't going to be much difference over all. There are also triple conversion receivers, and in some instances four stages are used instead of three. As far as R/C'ing is concerned those three and four stage thingys are a complete waste of money, just not too practical or useful.
As for the modulation method, PPM, PCM, PWM, 'pickle in a pear tree', etc, the transmitter and receiver both have to be of the same type. If not, the receiver will have absolutely no idea what the @#$ transmitter just said to do, so will most likely do nothing (if you're lucky). Is it possible to change from one mode to another? Probably, but the cost is going to be a huge factor, no idea if it would be worth it, not to me anyway.
- 'Doc
