What was found
DURING FLIGHT AT FL350, BOTH COMMS 1 & 2 DEVELOPED LOUD STATIC. COMMUNICATION WITH ATC WAS LOST. NEITHER COMMS 1 OR 2 COULD TRANSMIT OR RECEIVE, INTERCOM WAS OK. LOSS OF COMMS LASTED FOR 10 TO 12 MINUTES & STATIC CONTINUED DOWN TO FL200. STATIC DID NOT GO AWAY UNTIL COMPLETELY IN THE CLEAR. TROUBLESHOT COMMS 1 & 2 FAIL IN FLIGHT. PERFORMED ELECTRICAL BONDING TEST OF COMMS 1 & 2 ANTENNAS IAW MM 20-13-21-720-801-A. FOUND BOTH COMMS ANTENNAS TO BE OUT OF LIMITS. REMOVED ANTENNAS IAW MM 23-12-02-000-801-A. REINSTALLED COMMS 1 AND 2 ANTENNAS IAW MM 23-12-02-400-801-A. PERFORMED ELECTRICAL SURFACE BONDING PREP IAW MM 20-13-21-910-801-A. AFTER INSPECTION PERFORMED AN ELECTRICAL SURFACE BONDING PREP IAW MM 20-13-21-910-801-A. AFTER INSPECTION PERFORMED AN ELETRICAL BONDING TEST IAW PHENOM 300 MM 23-12-02-000-801-A. PERFORMED AERODYNAMIC SANDING OF COM1 AND COM 2 ANTENNAS IAW MM 51-21-03, PERFORMED OPS CHECK IAW MM 23-12-00-710-801-A. OPS CHECKED GOOD. NO DISCREPANCIES NOTED.