C172 PLT LOST COM WITH TWR BECAUSE HE DID NOT KNOW HOW TO OPERATE HIS AUDIO SELECTOR PANEL.

Narrative

JUST PURCHASED AIRPLANE. RELOCATING PARKING FROM HWV TO ISP. CHKED OUT AIRPLANE. DID 3 STOP-AND-GOES AT HWV TO BECOME DAY CURRENT; NO TOUCH-AND-GOES ON WKENDS. HAD SOME COM PROBS. BORROWED HEADSET FROM FRIEND WHO FLEW ME TO HWV. TOOK OFF HWV AND TRIED TO CONTACT NEW YORK APCH ON UNSELECTED RADIO. THEN TUNED SELECTED RADIO TO NEW YORK APCH THEN GIVEN BEACON CODE AND VECTOR 210 DEGS; 230 DEGS; 240 DEGS; THEN HANDED OFF TO TWR TO INTERCEPT FINAL APCH COURSE FOR RWY 33L; AT WHICH POINT I MUST HAVE TUNED THE UNSELECTED RADIO FOR TWR FREQ; ALL THE TIME RECEIVING ON BOTH RADIOS THINKING I MUST BE USING THE SELECTED RADIO TO XMIT; BUT ACTUALLY USING THE UNSELECTED RADIO. THEY ASKED ME TO IDENT; WHICH I DID; AND CLRED ME TO LAND AND SUBSEQUENTLY OVER TO GND CTL WHO SAID I SHOULD GIVE THE TWR A CALL; WHICH I DID. I AM GOING TO HAVE MY WHOLE AUDIO PANEL AND RADIOS CHKED OUT. BASICALLY IT WAS MY MISUNDERSTANDING OF THE AUDIO PANEL. I WAS THINKING SELECTING COM #1 OR #2 WITH THE TOGGLE SWITCHES WAS GIVING ME THAT RADIO BOTH TO XMIT AND RECEIVE WHEN IN ACTUALITY IT WAS ONLY RECEIVING IF THE SELECTOR KNOB WAS SELECTING THE SECOND RADIO. I WAS DUMB.