What was found
FLIGHT 2106. AFTER TAKEOFF AT ABOUT 400 AGL RECIEVED GND PROX WARNING. WHEN SELECTING FLAPS 0, LANDING GEAR AURAL WARNING ACTIVATED AND COULD NOT BE CANCELED. PERFORMED QRH NAP 38 CHECKLIST. RAD1 CB WAS PULLED OUT ON MCDU. AURAL WARNING CEASED AFTER CB ACTION. RETURNED TO FIELD. LANDING UNEVENTFUL. REMOVED FROM SERVICE AND PLACED ON MEL 34-31-00A. MEL CLEARED. PERFORMED RAD ALT OPS TEST AMM 34-31-00-710-801-A AND TCAS OPS CHECK 34-43-00-710-801-A PER FIM 34-43-00-810-804-A, BOTH CHECKS GOOD. REPLACED #1 SYSTEM RAD ALT ANTENNAS PER AMM 34-31-02-000/400-801-A, OPS CHECK GOOD. RETURNED TO SERVICE.