What was found
RADAR DISPLAYED NON-EXISTANT WEATHER IN A FIN BAND FOR 160MILES. GROUNDED-YES. WHILE TESTING, TEST PATTERN SHOWS CHATTER, OPEN C/B + INST MIG51A. REPLACED R/T WITH SERVICEABLE ONE, CLOSED C/B TEST STILL SHOWS CHATTER, OPEN C/B REINST ORIGINAL WX R/T. CLOSED C/B + REMOVED MIG51A, REF B737-800 MM 34-43-41-400-801. PULLED & TAGGED WRX C/B, REMOVED & REPLACED WRX ANTENNA DRIVE UNIT. REMOVED & RESET WRX C/B, PERFORMED INSTALLATION TEST GOOD, AMM 34-43-11/401.