Correct, the older MX-3000s may not work at all, or may work sporadically with the RFX-250. The newer MX-3000s have a narrow band transmitter which is required for the RFX-250 and they work great together.
As the post above suggests you could buy a new MX-3000 and MSC-400 or MRF-350. You could also use an RFX-150 on the MSC-400 and your existing (older) MX-3000
There are 10 types of people in this world, There are those who understand binary, and those who don't!
