C172 ENTERED WASHINGTON ADIZ WITHOUT CLRNC.

Narrative

I WAS FLYING CLOSE TO THE WASHINGTON; DC; ADIZ AND WAS CALLING FOR A XPONDER CODE. I RECEIVED A XPONDER CODE BUT WAS NOT GIVEN PERMISSION TO ENTER THE ADIZ. I WAS 1/2 NM FROM THE BOUNDARY WHEN I ASKED POTOMAC APCH FOR PERMISSION TO ENTER THE ADIZ. I WAS TOLD 'NEGATIVE; I DO NOT HAVE RADAR CONTACT; IDENT.' AT THIS POINT; THE GPS STILL INDICATING THAT I WAS OUTSIDE OF CLASS B AIRSPACE. MY ALTIMETER SHOWED THAT I WAS AT 4450 FT. THE CTLR TOLD ME THAT HE HAD A RADAR CONTACT (AFTER IDENT); BUT I HAD VIOLATED CLASS B AIRSPACE. HE CHEWED ME OUT AND TOLD ME TO MAINTAIN 4500 FT. I CHOSE NOT TO ARGUE WITH HIM AND ACKNOWLEDGED RECEIPT OF XMISSION THAT I HAD VIOLATED AIRSPACE. 10 MINS LATER; I HEARD THIS CTLR GIVE SOMEBODY ELSE ALTIMETER SETTING. IT WAS SIGNIFICANTLY DIFFERENT FROM MY SETTING. I HAD LISTENED TO JYO AWOS AND MY SETTINGS WERE CONSISTENT WITH THE AWOS. WHEN I LANDED AT JYO; MY ALTIMETER RPTED THE ALT OF THE ARPT WITH LESS THAN 10 FT ERROR. CONTRIBUTING FACTORS: I WAS TOO CLOSE TO THE CLASS B BOUNDARY. I DO NOT BELIEVE I VIOLATED THE AIRSPACE. IN ADDITION; THE POTOMAC APCH CTLR WAS GIVING OUT INCORRECT ALTIMETER SETTINGS; BUT FAILED TO GIVE ME ALTIMETER SETTINGS WHEN I FIRST CONTACTED HIM. THIS PROBABLY LED HIM TO BELIEVE I WAS AT A HIGHER ALT. THIS CTLR WAS ALSO EXTREMELY BUSY.