PRIMARY ELECTRICAL SUPPLY PROBLEM LEADS TO LOSS OF RADIO CONTACT.

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OVER MANY YRS AND HRS OF FLT IN ALMOST EVERYTHING FROM THE J-3 TO THE DC-3; WITH EMPHASIS ON THE LIGHTER END; I HAVE HEARD STORIES AND HAVE HADEXPERIENCES THAT WOULD ENHANCE SAFETY IF THEY COULD BE PASSED ON TO THE GA POPULATION. THERE WAS 1 TODAY WITH A COUPLE OF LESSONS. WE FILED IFR FROM A CTLED FIELD TO AN UNCTLED FIELD. THE WX WASN'T REALLY BAD;MARGINAL VFR. EVEN BEFORE WE STARTED TO TAXI; I HEARD EVERY ANNOYING STATIC ON THE RADIO. I TRIED TO FIND THE SOURCE; WITHOUT SUCCESS; BUT IT BECAME INTERMITTENT. DEP CTL TOLD US THAT OUR XPONDER WASN'T WORKING. I TRIED PRESSING IT INTO THE PANEL;I HAVE FOUND SOMETIMES THAT THERE'S A POORCONNECTION BTWN PLUG AND SOCKET. I SAW THE MONITOR LIGHT COME ON AND THE CTLR CONFIRMED THAT HE WAS RECEIVING THE SIGNAL. THE STATIC WAS STILL ANNOYING BUT I DISCOVERED THAT I COULD SILENCE IT BY TAPPING EITHER ONE OF OUR MICROPHONE BUTTONS UNTIL WE HEARD ANOTHER XMISSION; THEN IT WOULD START AGAIN; NOT THE FAMILIAR SYMPTOM OF A STUCK MICROPHONE. APCH CTL CLRED US FOR THE APCH; TELLING US THAT HE HAD LOST OUR XPONDER SIGNAL AND REMINDING US TO CANCEL OUR IFR WITH HIM OR THE GND. WE TRIED TO ACKNOWLEDGE RECEIPT OF HIS MESSAGE AND TO CALL THE ARPT ON UNICOM; BUT THERE WAS NO REPLY. AT LEAST WE RECOGNIZED RADIO FAILURE. LNDG AT THIS FIELD WAS NOT VERY IMPORTANT; THERE WAS A STRONG XWIND BLOWING ACROSS THE ONLY RWY; WE DIVERTED TO ANOTHER ARPT WITH MULTIPLE RWYS; AN UNCTLED FIELD; WITH A COFFEE SHOP; WE WOULD LAND THERE AND CONSIDER THE ALTERNATIVES. WE WERE IN VFR CONDITIONS. WE SWITCHED THE XPONDER TO 7700; THEN 7600; THEN TO 1200 AND HOPED THAT ATC WOULD UNDERSTAND. WE DID NOT THINK OF TURNING OFF ALL ELECTRICAL EQUIP EXCEPT THE XPONDER; WE WERE STILL THINKING ONLY OF RADIO FAILURE; PROBABLY BECAUSE OF THE STATIC. ENRTE TO THE OTHER FIELD; WE DID SOME TROUBLE SHOOTING AND DECIDED THAT THE TROUBLE WAS ELECTRICAL FAILURE; PROBABLY IN THE ALTERNATOR; NOT IN THE RADIOS AT ALL. OVER A CUP OF COFFEE AND A PIECE OF PIE; WE DISCUSSED THE CHANCES OF CORRECTING THE MALFUNCTION; AT LEAST CHKING THE BATTERY TERMINALS FOR A LOOSE CONNECTION OR THE ALTERNATOR. IT WAS 14 DEGS FAHRENHEIT WITH A WIND CHILL FACTOR SOMEWHERE BELOW '0.' IT DIDN'T TAKE LONGTO DECIDE THAT IT COULD BEST BE DONE AT OUR HOME FIELD; A CTLED ARPT; BY THE COMPANY MECH IN A HEATED HANGAR. WE CALLED THE TWR ON THE TELEPHONE AND WERE CLRED TO ENTER THE ATA; 2000 FT ABOVE FIELD ELEVATION; AND TO LOOK FOR LIGHT SIGNALS. ON THE WAY; WE SAW THE FUEL GAUGES GOING DOWN; CLOSE TO EMPTY; PROBABLY THE RESULT OF THE ELECTRICAL FAILURE. WE WERE PRETTY SURE THAT WE HAD PLENTY OF FUEL; BUT WAS THERE SOMETHING ELSE GOING ON? WE CIRCLED THE FIELD ONCE AND DIDN'T SEE A LIGHT; THE GAUGES WENT TO '0.' ISAID TO MY FRIEND 'WE ARE LNDG; NOW; THIS IS ABONA FIDE EMER.' THEN WE SAW THE GREEN LIGHT ANDLANDED. LATER; MUCH LATER; WE THOUGHT OF FAR 205; INOP EQUIP; AND THE ELECTRICAL FUEL PUMP. IF THE ENG DRIVEN FUEL PUMP HAD FAILED? THERE MUST BE SOMETHING OF VALUE IN THIS STORY; PERHAPS; TO BE SUSPICIOUS OF HVY STATIC IN THE RADIO; FOR A START; AND THE FARS. THE REGS; PROBABLY MOST OF THEM; WERE WRITTEN AS A RESULT OF PLT'S EXPERIENCES.