Hey, did you manage to get a solution for your VHF radio issue? I'm also having trouble using the VHF radio (COM 2) in the Viper. In single player missions I'm unable to give orders to wingman, because I can't get COMM 2 to work.
C&I knob set to UFC, Audio 1 controls under the throttle (COMM 1 and COMM 2) are set to upward on/enable position, VHF frequency is correct (as defined in mission editor and mission briefing), and pressing VHF transmit button doesn't work - the UHF in the DED flashes indicating the transmission was not in VHF. Am I missing something? Or the VHF radio is really not working?
PS.: The viper is my first full fidelity mod, I've been flying only FC3 planes til now. So pardon me if my question is something obvious to fix.