PLT OF SMA ACFT DEVIATED FROM ASSIGNED ALT DUE THE ACFT COM RADIO MALFUNCTION.

Narrative

I REALIZED I HAD A RADIO FAILURE AS I WAS HANDED OFF FROM CHARLESTON APCH TO ZID. I COULD RECEIVE; HOWEVER; I COULD NOT XMIT -- CARRIER NO VOICE. APPROX 10 MINS BEFOREHAND; I WAS GETTING A HIGH-PITCHED HUM OVER ALL MY HEADSETS AND ACFT SPEAKER THAT HAD INCREASED IN INTENSITY TO ANNOYING PROPORTIONS. I WAS AT THE POINT OF HDOF PASSING OVERHEAD AN ARPT. I DID NOT WANT TO CONTINUE THE FLT. I COULD STILL HEAR ZID. BEING OVERTOP THIS ARPT; MY THOUGHT WAS TO PROCEED VFR; LAND QUICKLY AND TO CALL IN. I DID NOT SQUAWK 7700/7600 IMMEDIATELY BECAUSE; IN 1 MIN I WOULD HAVE BEEN OUT OF RADAR COVERAGE EITHER ON THE GND OR CLOSE TO LNDG AND ALL ATC MIGHT'VE SEEN IS THE EMER CODE 7700 AND THEN I DROP OUT OF SIGHT. IN RETROSPECT; I WAS OUT-THINKING THE CTLRS. AS I BANKED TOWARD THE ARPT IN QUESTION; DSNDING; I COULD NOW MAKE OUT THAT THIS ARPT HAD NOT YET OPENED. THERE WERE NO FACILITIES AND NO VISIBLE X'S ON THE RWY; AND I WOULD NOT BE ABLE TO CALL ANYONE. AT PRECISELY THIS MOMENT; ZID ASKED ME IF I WAS GOING BACK TO CRW TO IDENT. I FIGURED AT THAT POINT THAT WAS THE RIGHT THING TO DO. I RESPONDED AND HE CLRED ME TO CRW AT 4000. ALSO; AT THIS POINT; BEING AWARE OF HAVING LEFT MY ORIGINAL ALT TO MAKE A VFR DSCNT AND LNDG I HAD BETTER SQUAWK 7700/7600; BUT AT PRECISELY THIS MOMENT; ZID ASKED IF I HAD AN EMER. I DID NOT IDENT; RESPONDING IN THE NEGATIVE. SO; AT THAT POINT IT SEEMED CONTRADICTORY TO THEN SQUAWK 7700; AND WITH 1-WAY RADIO COM POSSIBLE; COUPLED WITH MY ABILITY TO REPLY BY XPONDER AND MY PROX TO CHARLESTON; I DECIDED NOT TO CHANGE MY CODE. FROM THIS POINT FROM THE TIME I FIRST REALIZED MY RADIO FAILURE IT WAS APPROX 2 MINS. THIS ALL HAPPENED VERY QUICKLY. THERE WAS NO CONFUSION THAT FOLLOWED. I WAS EASILY HANDED BACK TO CHARLESTON APCH WITHOUT A TFC CONFLICT. TFC AROUND CHARLESTON WAS LIGHT AND I EASILY LANDED WITHOUT INCIDENT OR DIFFICULTY. I WAS THEN ASKED TO CALL THE TWR. I DID SO AND TALKED TO THE SUPVR. HE MADE IT CLR THAT IT WOULD'VE BEEN EASIER FOR THEM IF I HAD SQUAWKED 7700/7600 IMMEDIATELY BEFORE LEAVING MY ALT.