RE: Does a fully Synthesized Tx work with a crystal fitted Rx?
I haven't owned a JR radio as of yet, but I can take an educated guess here. S-PCM and Z-PCM are probably different kinds of JR PCM modulation. One is likely the current type and the other is likely an older type that was included to be compatible with older PCM receivers.
Hopefully a JR owner or two can fill in some blanks here for us...