RE: Jr Fm to 2.4g? I know nothing!
Hold up...
There is a caveat. Yes, any of the current systems technically will work with your servos (I'm an Airtronics guy, so I'll tell you to look carefully at the SD10 radio and the cost of additional Receivers. BTW, Airtronics offers Rx's in bulk packs for even less). That said, you MAYfind that some of your older Analog servos do NOT work well with 2.4Ghz systems. I'm not 100% sure of what's happening technically, but in simple terms...they can't handle the fast refresh rate that the new radio's are putting out. This is true of ALL the brands, but there is no definitive guide (yet) that says which of the older servos do or don't behave well with various systems.
You'll notice that Digital servos are all the rage. There's a reason for that...they all work with the 2.4 systems.
MOSTof my existing analog servos DO work with my ATX transmitter and would probably work with other 2.4 systems as well. Just a few of the older, slower servos seem to behave badly.
I don't want to throw you off the course of getting a new system. It's very much worth the investment and most of your stuff (and possibly all of it) will work fine. Just have your eyes open that some may not and be prepared.
BTW, the failure is evident on the ground when you first try them. It's not something that will sneak up on you.They'll either function properly or they won't. No mystery.
-Mark