I rememeber with the DX6 people were having a similar problem and they were losing contact. If I remember correctly it was the receiver not having enough voltage and locking out the radio. Horizon designed the receiver to run on a 6 volt pack and when people used a 4.8 volt pack and it lost voltage from either needing a charge or a high current load it would lock out. Again I dont know if the DX7 is designed the same way but if it is then it is something to consider especially if you were running a 4 cell receiver pack.