Any PPM receiver is usable with the 4000 as long as they are the same shift as JR. For opposite shift (which IIRC Futaba is) Ernie Pritchard (and perhaps someone in England) can do a simple mod where he installs a switch to select shift. I have used both positive and negative shift PPM RXs with my 4000 and they work perfectly. However, now that IPD MPX receivers are available, I would use nothing less for high dollar models.