Reciever must be paired up with a transmitter.
Reciever are not universal fitted with transmitters.
Unless youre transmitter is one that has a module in it you have to stick to its brand and frequency.
But isnt the MX-3 already 2.4 and has short antenna ?
Your cheapest 2.4ghz combo i think.
Next to the Losi RTR 2.4 transmitters that use spektrum recievers
Also Spektrum are easier to get ur hands on since alot more people seem to have them =D