What was found
PRIOR TO DAWNA, TRANSMITTED ON 2 FREQUENCIES WITH NO RESPONSE FROM ATC. AFTER DAWNA COULD NOT CONFIRM IF WE`RE TRANSMITTING OR RECEIVING. TRIED ALL MICS ON ALL COM AND NAV RADIOS. TRIED ALT POSITION, MASK , HAND MIC AND PTT SWITCH ON MIC SELECTOR PANEL. REMOVED AND REPLACED THE REMOTE ELECTRONICS CONTROL UNIT. ALL VHF'S OP S NORMAL CONTACTING OPS.