MOONEY PLT HAS LOST COM DURING DEP AND COMES VERY CLOSE TO P-40 PROHIBITED AREA.

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THE FLT WAS A PART 91 TRIP IN MY PERSONAL PLANE FROM MY 3 DAY WORK WK FOR A PART 135 OP. I WAS ON AN IFR FLT PLAN FROM BWI TO AN UNCTLED FIELD NEAR PITTSBURGH. I HAD RECEIVED MY BRIEFING AND FILED MY FLT PLAN VIA DUATS JUST PRIOR TO THE FLT AND WAS AWARE OF THE EXPANDED TFR AROUND P-40. WHEN I WAS READY TO DEPART; I SWITCHED FROM GND TO THE TWR FREQ AND FOUND THAT THE FREQ SEEMED TO BE BLOCKED. I MADE MY CALL ANYWAY BUT HEARD NO RESPONSE. I SWITCHED BACK TO GND AND IMMEDIATELY HEARD 'MOONEY CLRED FOR TKOF RWY HDG.' HEARING THIS; I ASSUMED THERE WAS A PROB WITH THE TWR FREQ AND NOT MY RADIO BECAUSE THE COMS FROM GND CTL WERE NORMAL. SOMEWHERE AROUND LIFTOFF; I WAS TOLD TO CONTACT THE FREQ AGAIN. WHEN I DID; THE RESPONSE FROM THE TWR WAS GARBLED. THAT WAS THE LAST THING I WAS ABLE TO HEAR. WHEN I THOUGHT I SHOULD HAVE BEEN HANDED OFF TO DEP; I MADE A CALL BUT WAS UNABLE TO GET A RESPONSE EITHER. I THEN SQUAWKED 7600. SINCE IT WAS VFR; AND I COULD CONTINUE VFR I DECIDED TO DEPART THE AREA PER MY FPR. IF I WAS UNABLE TO RE-ESTABLISH COMS; I WOULD FIND A SUITABLE PLACE TO LAND. I WAS USING A HAND MIKE BECAUSE THE PUSH-TO-TALK SWITCH ON THE YOKE HAD GOTTEN A LITTLE LOOSE IN THE SOCKET AND WAS DIFFICULT TO DEPRESS. THE NOISE OR STATIC I COULD HEAR FROM MY RADIOS SOUNDED SIMILAR TO A STUCK MIKE BUT NOT EXACTLY. I DIDN'T THINK MY MIKE WAS STUCK BECAUSE I COULD HEAR THE AUDIO CLICK WHEN I PRESSED THE SWITCH AND ALSO WHEN I RELEASED IT. THIS WAS A VERY BAFFLING AND CONFUSING CONDITION. I HAVE HAD STUCK MIKES BEFORE BUT THIS CONDITION WASN'T THE SAME. I WAS STILL ON RWY HDG; RWY 33R; WHILE TRYING TO SORT THIS OUT AND BEGAN TO LOSE MY POSITIONAL AWARENESS. BEING THAT IT WAS A BEAUTIFUL CLR DAY FURTHER DIMINISHED MY CONCERN FOR CLRLY MONITORING MY POS. MY CLRNC WAS FOR VECTORS TO V-214 GRV; DIRECT IHD; DIRECT. CLB TO 4000 FT EXPECT 6000 FT 10 MINS AFTER. I EXECUTED THE CLBS AS EXPECTED AND TUNED IN MRB THE FIRST FIX IN THE AIRWAY. INSTEAD OF TURNING BACK TO THE S AND INTERCEPTING V-214 LIKE I SHOULD HAVE; I WENT DIRECTLY TO IT. I DIDN'T THINK I WAS THAT FAR N OF COURSE; BUT I LOST TRACK OF THE TIME I WAS ON RWY HDG AS WELL. HAD I TOOK NOTICE OF THE HDG TO THE VOR; I WOULD HAVE REALIZED HOW FAR OFF COURSE I WAS. AS IT WAS THOUGH; I BECAME TOO ENGROSSED IN SOLVING THE PROB. AS THE FRUSTRATION WITH THE PROB INCREASED; CLR THINKING ABOUT WHAT I SHOULD BE DOING DECREASED. I HAD THE AUTOPLT ENGAGED IN HDG MODE AFTER CTRING THE NEEDLE BUT WAS NOT MONITORING MY COURSE CLOSELY AND WOUND UP N OF MY INTENDED RTE. RESOLVING THE PROB BECAME THE FOCUS OF MY ATTN INSTEAD OF NAVING. OCCASIONALLY THE BACKGND NOISE WOULD CLR UP MOMENTARILY. ONCE WHEN I MOVED THE SWITCH FROM COM #1 TO COM #2 THE BACKGND NOISE CLRED UP MOMENTARILY. UPON XMITTING; IT WAS BACK THOUGH. THIS ANECDOTAL EVIDENCE OF THE PROB TURNED OUT TO BE COINCIDENTAL; AND IT FURTHER DISTR ME FROM WATCHING MY COURSE. THEN AT ONE POINT; I MUST HAVE INADVERTENTLY DISCONNECTED HDG MODE; LEAVING THE AUTOPLT WITH JUST THE FLT DIRECTOR ENGAGED. DUE TO A HEAVIER FUEL LOAD IN THE R WING; THIS CAUSED THE ACFT TO DRIFT N AS WELL. AT THE EXPENSE OF TRACKING THE APPROPRIATE COURSE; I ULTIMATELY DISCOVERED THE PROB. IT WAS THE ONE I SHOULD HAVE CONSIDERED TO BEGIN WITH. I HAD TRIED THE PUSH-TO-TALK SWITCH PREVIOUSLY AND COULD HEAR IT CLICK TO XMIT AND RELEASE SO I HADN'T GIVEN IT ANY FURTHER THOUGHT. THIS TIME I WIGGLED IT SIDE-TO-SIDE AND COULD DETECT A CHANGE IN THE STATIC; ALMOST ELIMINATING IT AS I HELD IT. I HAD A SMALL SCREWDRIVER WITHIN EASY REACH SO I REMOVED THE SCREWS FROM THE TRIM SWITCH BASE TO ACCESS THE PUSH-TO-TALK SWITCH AND SAW THAT 1 WIRE HAD COME DETACHED AND WAS SHORTING WITH THE OTHER. AFTER PULLING IT AWAY; COMS WERE NORMAL. I RE-ESTABLISHED CONTACT WITH POTOMAC APCH AND WAS TOLD I WAS VERY CLOSE TO RESTR AIRSPACE AND TO TURN TO HDG 180 DEGS. I WAS INSTRUCTED TO INTERCEPT MY FPR AND CONTINUED TO DEST. FATIGUE HAS TO BE CONSIDERED AS WELL. MY DUTY TIME THE NIGHT BEFORE BEGAN AT XA30 AND ENDED ABOUT 1 HR BEFORE THIS FLT AT XJ00. I DID NOT FEEL OVERLY TIRED; BUT FATIGUE IS AN INSIDIOUS THING.