PLT OF A PA28-180 IS UNAWARE OF RADIO PROB; BELIEVES TWR IS CLOSED AND ENTERS CLASS D AIRSPACE WITHOUT CLRNC. HE HAS AN NMAC WITH ACFT DEPARTING OPPOSITE DIRECTION.

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I WAS RETURNING VFR FROM VYX TO MY HOME ARPT OF PWK. I HAD JUST CLRED NW OF DPA CLASS D WITH NO INCIDENT AND GOOD COMS WITH DPA TWR. IN ORDER TO REMAIN WELL CLR OF ORD CLASS B AND SIMPLIFY NAV; I PLANNED TO FLY AT 2000 FT MSL FROM DPA VOR TO OBK VOR AND THEN TO PWK. I TUNED IN PWK ATIS ON THE COM #2 RADIO AND WROTE DOWN THE PERTINENT INFO. I TUNED THE COM #1 RADIO TO PWK TWR AND FLEW ON FOR A FEW MINS UNTIL I GOT CLOSER TO OBK. I CALLED PWK TWR ON COM #1 WITH MY POS; INTENDED RTE OF ARR FROM OBK; AND INTENT TO LAND. I HEARD NO REPLY FROM THE TWR SO I WAITED A MOMENT AND THEN CALLED AGAIN STATING MY POS AS 'OVER NORTHBROOK VOR' AND AGAIN THAT I WAS INBOUND FOR LNDG. AGAIN I HEARD NO REPLY; SO I VERIFIED THE TWR'S FREQ FROM MY (CURRENT) SECTIONAL AND CHKED THAT THE RADIO MADE NOISE IN ITS 'TEST' POS; WHICH IT DID. I THOUGHT TO CHK PWK'S HRS OF OP SO I LOOKED IN THE (CURRENT) AFD AND DIDN'T IMMEDIATELY FIND THE TWR'S HRS. NOT WANTING TO SPEND TOO MUCH TIME 'HEAD DOWN' IN A BUSY VFR ENVIRONMENT; I LOOKED AT THE GUIDE SHEET FOR PWK WHICH I HAD ATTACHED TO MY KNEEBOARD AND SAW THE TWR CLOSING TIME LISTED AS 'XA00.' I LOOKED AT MY WATCH; WHICH WAS SET TO ZULU TIME; AND SAW THAT IT WAS SEVERAL MINS AFTER XA00. I ALSO LOOKED AT AND AROUND THE ARPT; WHICH WAS NOW IN SIGHT; AND SAW NO TFC. BELIEVING THAT THE TWR HAD JUST CLOSED AND I WAS NOW DEALING WITH A NONTWRED ARPT; I MADE MY NEXT CALL TO 'PALWAUKEE TFC' ON THE CTAF/TWR FREQ OF 119.9 PER NONTWRED SELF-ANNOUNCE PROC. I GAVE MY DISTANCE FROM THE VOR AND RPTED INBOUND WITH INTENT TO LAND. I CALLED AGAIN SHORTLY; GIVING POS AS 5 MI OUT; 'LNDG RWY 12; CORRECTION 16.' ON SHORT FINAL; I CALLED SHORT FINAL LNDG RWY 16. I LOOKED UP FROM MY VISUAL CHK OF THE GS TO SEE A LIGHT SINGLE ENG LOW WING ACFT; BLUE AND WHITE; MAKING A CLBING L TURN ABOVE AND TO THE R OF ME. THE OTHER ACFT WAS CLR OF ME AND OUR FLT PATHS WERE DIVERGENT AT THE TIME SO NO EVASIVE WAS NECESSARY. I REMEMBER BEING VERY STARTLED AND THINKING THAT THE OTHER ACFT HAD MADE A SERIOUS ERROR BY A) NOT ANNOUNCING HIS/HER ACTIONS OVER THE CTAF; AND B) DEPARTING ON THE OPPOSITE RWY FROM THE ONE I HAD TWICE ANNOUNCED MY INTENT TO LAND ON. SOMEWHAT RATTLED; I MADE MY LNDG ON RWY 16 AND TURNED OFF RWY 16 TO TXWY E AND ANNOUNCED 'CLR OF RWY 16 ON TXWY B' (THE 2 SIGNS WERE CLOSE TO EACH OTHER). I LATER CORRECTLY ANNOUNCED THAT I WAS 'ON TXWY E HEADED TO AREA X;' THEN PARKED AND ANNOUNCED CLR OF ALL TXWYS. AFTER I STOPPED THE ENG AND WAS COLLECTING MY BELONGINGS; THE OTHER ACFT'S SILENCE ON THE RADIO AND THE LOSS OF SEPARATION BEGAN TO CONCERN ME. A TRUCK FROM ONE OF THE FBO'S ON THE FIELD ARRIVED AND INFORMED ME THAT I WAS TO CALL THE TWR. POSTEVENT: I CALLED THE TWR AND THE PERSON WHO REPLIED ASKED ME IF I 'KNEW THAT WE HAD A TWR HERE.' I SAID THAT I DID; BUT BELIEVED THEM TO BE CLOSED AT XA00Z. HE INDICATED THAT THE TWR WAS ACTIVE UNTIL YY00 (XA00 LCL) AND THAT 'THIS IS A VERY BUSY ARPT.' HE FURTHER INDICATED THAT MY XMISSIONS HAD BEEN RECEIVED; AS SOMEONE (EITHER A CTLR OR ANOTHER PLT) HAD JOKED ABOUT MY ANNOUNCING MY RADIO CALLS TO 'PALWAUKEE TFC.' HE ALSO ASKED IF I HAD HEARD HIS INSTRUCTIONS TO ME AND I REPLIED THAT I HAD NOT. ANXIOUS; WANTING TO SOLVE THE PROB; AND RECALLING SOME ODD BEHAVIOR WITH THE FREQ SELECTOR ON COM #1 (SEE BELOW). I SPECULATED ON THE POSSIBILITY OF THERE BEING SOME TROUBLE WITH THE RADIO. HE REMINDED ME OF NORDO PROCS; WHICH I KNOW; AND SAID THAT HE WAS GOING TO HAVE TO RPT THIS EVENT 'IN CASE ANYONE EVER ASKS WHAT I DID ABOUT IT...' BECAUSE IT WAS 'HIS JOB ON THE LINE; TOO.' THE NEXT DAY; I TESTED THE COM #1 RADIO ON THE GND WITH THE AID OF A CELLULAR PHONE AND AN EMPLOYEE AT THE FBO. THE RADIO MADE ITS APPROPRIATE NOISE IN 'TEST' MODE; AND PICKED UP ATIS JUST FINE. WHEN I CALLED THE FBO ON THEIR PVT FREQ; THE EMPLOYEE HEARD ME AND I HEARD HER REPLY. I TWICE HAD HER MONITOR THE TWR FREQ WHILE I CALLED FOR A RADIO CHK. THE FBO EMPLOYEE SAID THAT SHE DID NOT HEAR MY XMISSION; AND THE TWR DID NOT REPLY. WHILEI'M NOT AN AVIONICS TECHNICIAN; THE RADIO OBVIOUSLY WAS OPERATING IN AN INTERMITTENT MANNER: THE MECHANICAL FREQ INDICATOR SEEMED TO BE 'SLIPPING' ON ITS GEARS IN SOME FASHION; AND ONLY FOR A CERTAIN RANGE OF FREQS. THIS WAS PROBABLY WHY I HAD NO DIFFICULTY COMMUNICATING WITH THE OTHER FACILITIES PREVIOUSLY; AND WAS A DIFFICULT SIT TO DETECT AND DIAGNOSE ON THE GND; LET ALONE INFLT. BACKGND; CONTRIBUTING FACTORS; PREVENTION: THE ACFT I OPERATED WAS A RENTAL; WITH OLDER MECHANICAL-INDICATOR RADIOS. WHILE I'M NOT A VERY HIGH-TIME PLT; I HAVE THE MAJORITY OF MY TIME IN A MORE MODERN ACFT WITH BENDIX/KING DIGITAL- DISPLAY RADIOS AND HAVE ALWAYS BELIEVED THAT A CERTIFIED RADIO WILL 'DO WHAT IT SAYS' AND EITHER WORK OR NOT WORK. I AM FAMILIAR WITH THE CLASS D REQUIREMENTS FOR 2-WAY COM; AND WITH NORDO PROCS. IF I HAD SUSPECTED RADIO DIFFICULTIES; I WOULD HAVE CIRCLED AND LOOKED FOR THE LIGHT GUN; OR JUST TRIED CALLING THE TWR WITH COM #2.