A C177 SINGLE PLT ENTERED THE DC ADIZ.

Narrative

WHILE APCHING THE WASHINGTON; DC; ADIZ FROM THE SW; I CALLED POTOMAC APCH FOR A SQUAWK CODE FOR ENTRY. I WAS GIVEN A SQUAWK CODE WHICH WAS HEARD BY MYSELF AND A PAX. POTOMAC APCH WAS VERY BUSY AND THE CTLR WAS WORKING MORE THAN 1 FREQ. I WAS NOT RADAR IDENTED BY THE CTLR UPON PENETRATION OF THE ADIZ; BUT DIDN'T NEED TO BE IN TERMS OF THE NOTAM SINCE I HAD A DISCRETE BEACON CODE AND WAS IN 2-WAY RADIO COMS WITH ATC. AFTER 4 CALLS TO APCH INSIDE THE ADIZ WITH NO ANSWER; I SUSPECTED RADIO FAILURE BUT THE CTLR ANSWERED MY LAST CALL. HE ASKED MY POS. I RESPONDED 'ABOUT TO ENTER CLASS D' AT MANASSAS. HE ASKED IF I WAS SQUAWKING MY ASSIGNED CODE. I RESPONDED THAT I WAS GIVEN/SQUAWKING; AS ASSIGNED. THE CTLR RESPONDED 'SQUAWK THE PROPER CODE.' I DIALED IN THE CODE; AT WHICH POINT I WAS NEARLY INSIDE THE MANASSAS CLASS D. I ASKED THE APCH CTLR FOR A FREQ CHANGE TO THE TWR AND AGAIN GOT NO RESPONSE. AT THIS POINT (APPROX 4 MI FROM MANASSAS ARPT); I NOTICED A LONG EZ LESS THAN 1/2 MI ON A COLLISION COURSE. I TOOK EVASIVE ACTION AND WE MISSED BY ABOUT 300 FT LATERALLY AND 0 FT VERTLY. SINCE THE APCH CTLR WAS NOT ANSWERING MY LATEST CALLS; I SWITCHED TO TWR ON MY OWN AND LWOC. THIS SIT COULD HAVE BEEN AVOIDED IF POTOMAC HAD ASSIGNED A DEDICATED CTLR TO WORK THE 120.82 FREQ; WHICH IS SOLELY FOR ADIZ ARRS/DEPS AT MANASSAS. THIS IS THE FIRST TIME SINCE THE ESTABLISHMENT OF THE 120.82 FREQ THAT I HAVE HEARD A CTLR WORKING OTHER FREQS AS WELL AS 120.82 ON A VFR SATURDAY (WHICH IS PEAK TIME FOR MANASSAS). ALSO; I WILL CONFIRM THAT I AM RADAR IDENTED IN THE FUTURE BEFORE ADIZ PENETRATION; EVEN THOUGH THE LAW DOESN'T REQUIRE IT.