GA SMA LOST ELECTRICAL PWR AND HAD TO DECLARE AN EMER TO GET ZOA FLT ASSIST.

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WAS FLYING VFR FROM L45 TO SAN JOSE INTL. WX WAS 1500 SCATTERED; 3000-7000 OVCST. FREEZING LEVEL WAS 4500-6500. APPROX 20 MI SE OF SALINAS MY VOR STARTED ACTING UP. I SPENT 5-10 MINS TRYING DIFFERENT FREQS AND ALTS. STATIC BUT NO SIGNAL. BECAUSE OF THE BAD VISIBILITY AND UNCERTAINTY WHERE I WAS I CALLED OAKLAND RADIO. OAKLAND COULD NOT COPY MY MODE C. THERE WAS A HOLE ABOVE ME SO I CLBED TO TRY TO GET IT TO WORK. WHILE CLBING; OAKLAND RPTED THAT THEY COULD NOT HEAR ME ANYMORE. IMMEDIATELY AFTER THIS THE RADIO FREQS ON THE COM RADIO JUMPED OFF (THEY ARE PROGRAMMED; NOT SWITCHED). I REALIZED THAT I HAD AN ALTERNATOR FAILURE AND LOW BATTERY AS THE SOURCE OF THE PROBLEMS. I SHUT OFF ALL ELECTRICAL EXCEPT THE COM RADIO AND MODE C. WITH ALL OF THIS GOING ON I LOST SIGHT OF THE GND AND WAS VFR ON TOP AT 7000 FT. ALSO I WAS PICKING UP SLIGHT ICING. ALSO; I REALIZED I PROBABLY HAD VERY LITTLE BATTERY LEFT AND NO LONGER HAD OAKLAND'S FREQ. I CALLED MAYDAY ON 121.5 AND EVENTUALLY GOT OAKLAND BACK. WITH THEM; I THEN WENT THROUGH THE CLOUDS TO LAND AT MONTEREY. ACTIONS ARE LISTED ABOVE. INACTIONS WERE: 1) I SHOULD HAVE PICKED UP THE ALTERNATOR FAILURE MUCH SOONER. I HAVEN'T CHKED IT IN THE PAST ON PANEL SCANS. 2) SHOULDN'T HAVE FLOWN IN SUCH BAD WX.