I have a 2.4 TX that came with my CX 2 helicopter its a LOW Power unit. I suspect a great many of the less expensive units are just that low power and lack the range of their bigger brothers.

Some time ago I called Horizon and questioned them if my low power unit could be used as a buddy box for my DX7 the reply was no. There obviously are differences in these units, the short range units are just that.