What was found
AIRCRAFT DEPARTED, CREW SWITCHED THE NR 1 TRANSPONDER FREQUENCY FROM TOWER TO DEPARTURE & WAS NOTIFIED THAT THEIR TRANSPONDER SIGNAL WAS INTERMITTENT. CREW SWITCHED OVER TO THE NR 2 TRANSPONDER & DEPARTURE NOTIFIED THEM THAT THE NR 2 TRANSPONDER SIGNAL WAS NOT BEING RECEIVED. ACFT RETURNED. PERFORMED AN OPS TEST ON THE NR 1 & 2 TRANSPONDERS WITH NO DEFECTS NOTED. ACFT WAS RETURNED TO SERVICE & AN CHECK FLIGHT WAS ACCOMPLISHED WITH NO DEFECTS NOTED. ACFT HAD SEVERAL SUCCESSFUL FLIGHTS SINCE THE RTS.