>Many 2-channel RC transmitters contain the Signetic chip (NE5040??) which
>is actually a 7-channel encoder.  You just need to connect additional
>pots to the unused pins.  Such a modified transmitter would still be
>"dumb," so including a PIC for digital processing makes a lot of sense.

For a simple data transmission of 7 termocouples in a electric motor (from
the rotor) I used the Signetics NE5044 (rx) and NE5045 (tx) couple. The
design was extremely easy following the data sheets, and there was no
problem with the "hard" environment. But there are little possibilities
beyond the specifications of this design. Perhaps is more convenient for
you a totally digital measure and computation of the channels... all in a
single PIC IC.