You shoudn't need to turn on the radio if you have the proper connection on the trainer plug. The radio will turn on automatically with the rf module disabled in trainer mode once the plug is pushed in. You will still need to power it using the batteries since the Reflex USB cable does not supply power to the radio. However, with the rf module disables, the radio uses much less energy and should last between 2 to 3 time as long. I've upgraded my 9CHP to 1850mah Nimah batteries and if I just use it on Reflex, the batteries will last between 15 - 16 hours.