As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOTH COMMS AND NAVS QUIT IN STATIC PRECIPITATION. THE COMM WOULD BECOME UNREADABLE AND BOTH NAV'S WOULD FLAG AND LOSS OF L/R DEVIATION. TESTED AIRCRAFT WITH DAYTON GRANGIER HIGH-VOLTAGE TESTER AND FOUND LORAN ANTENNA SOURCE OF NOISE. REMOVED AND REPLACED WTIH HIGH-SPEED BLADE STYLE ANTENNA, PN 14663-03. FLIGHT TESTED AND PROBLEM CORRECTED. REF WO NR A5606.