RE: cheaper 2.4 full range with trainer
The Spektrum, Futaba, Airtronics, and Hitec 2.4 systems have Trainer Cord capability. The Trainer or Buddy Box does not transmit so it dose not need an RF section. You can pick up cheap 72Mhz Tx's that have RF Modules and use 2.4 conversion modules. Most of them have Buddy Cord jacks.