SMA HAS MIKE PROBLEM ALONG WITH DETERIORATING WX. SQUAWKS 7700 AND CLBS THROUGH OVCST.

Narrative

THE WX FOR SAN JOSE WAS RPTED AS 1300 FT AND 7 MI VISIBILITY. I RECEIVED A CLRNC OUT OF THE ARSA INSTRUCTING ME TO DEPART N; MAKE A R TURN; FOLLOW HWY 101 S TO S COUNTY ARPT. ABOUT 6 MI S OF SAN JOSE; THE WX DETERIORATED RAPIDLY TO LESS THAN 3 MI IN HAZE AND SMOG. I TRIED TO CALL TWR; THEN BAY APCH; BUT WAS UNABLE TO REACH EITHER FACILITY. LATER I LEARNED THAT THE YOKE MICROPHONE BUTTON ON THE ACFT WAS DEFECTIVE AND BLOCKED OUT THE HAND MIKE I WAS USING. THE FLT VISIBILITY CONTINUED TO DECREASE AND RATHER THAN TURN AROUND INTO SAN JOSE TFC IN REDUCED VISIBILITY AND WITHOUT RADIO COMS OR MAKING TURNS IN A VALLEY WITH STEEP MOUNTAINS ON BOTH SIDES; I ELECTED TO CONTINUE ON MY ASSIGNED HDG AND CLBED THROUGH A 300 FT CLOUD LAYER. I SET 7700 ON THE TRANSPONDER AND WAS THROUGH THE CLOUD LAYER IN ABOUT 30 SECONDS. AFTER ARRIVING VFR ON TOP; I TUNED IN 7600 TO SIGNIFY THAT I HAD LOST COM WITH ATC. I WAS ABLE TO REESTABLISH COM WITH ATC THROUGH CASTLE APCH A FEW MINS LATER. I INVOKED MY EMER AUTHORITY AS PIC BECAUSE I FELT THAT IT WOULD BE MORE DANGEROUS TO FLY AROUND IN A VALLEY IN LOW VISIBILITIES OR RETURN TO THE SAN JOSE ARPT WITH NO RADIO AND WX CONDITIONS I HAD NO WAY OF CONFIRMING. IF THE COMS PROBLEMS CONTINUED I WOULD HAVE LANDED AT AN UNCTLED ARPT. I KNEW THAT I HAD TERRAIN CLRNC IF I MAINTAINED MY ASSIGNED HDG AND I ALSO KNEW THAT THE CLOUD/SMOG BANK WAS ONLY A FEW HUNDRED FT THICK. I HAVE READ ABOUT NUMEROUS ACCIDENTS WHERE PLTS HAVE CONTINUED VFR IN IFR CONDITIONS BECAUSE THEY WERE EITHER NOT INST QUALIFIED; OR WERE AFRAID OF VIOLATIONS WITH THE FAA. OUR OFFICE HAS A POLICY THAT WE DO NOT FLY SINGLE PLT IFR AND THIS IS WHY I DID NOT FILE FOR AN IFR CLB TO VFR ON TOP.