It's still there, Mike.

Pete, nothing in the schematic I posted has been obsolete or will be anytime soon. The part that my schematic replaces that is MUCH simpler, (the dedicated transceiver chip) has been obsoleted-so I have drawn it using the still very widely available, in production, discrete parts instead. (obsolete part is an 8-pin surface mount chip, my solution is completely available in through-hole if you want it as an 8 pin DIP, two TO-220 and two TO-92 parts.)

I've got 4x mode working right now, and have it running on the bench PCM next to a noise generator to test for error detection and correction. I'm gonna let it run for a few hours and see how the error rates look.