LOSS OF RADIO CONTACT CAUSES PLT TO RETURN LAND WITHOUT REVISED CLRNC.

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I DEPARTED RWY 28 FROM DPA WITH AN INST CLRNC FOR A LCL FLT TO PWK. FOLLOWING INSTRUCTIONS; I TURNED R TO A HDG OF 360 DEGS AND CONTACTED CHICAGO DEP/APCH (FREQ 133.5). UPON REACHING MY ASSIGNED ALT OF 3000 FT MSL. I WAS INSTRUCTED TO GET ATIS AT PWK AND RPT BACK ON FREQ. I SUCCESSFULLY RECEIVED ATIS FROM PWK. WHEN I TRIED TO RE- ESTABLISH CONTACT WITH THE CTLR; I COULD NOT DO SO. WHEN I PRESSED THE PUSH-TO-TALK SWITCH ON THE YOKE WITH MY L THUMB; I COULD NOT HEAR MY VOICE IN MY HEADSET. THERE WAS NO RESPONSE TO MY ATTEMPTS TO XMIT. AT THIS POINT; I NOTICED SOMETHING ELSE UNUSUAL. AFTER I RELEASED THE PUSH-TO-TALK SWITCH; I COULD HEAR THE SOUND OF AN OPEN CHANNEL FOR ABOUT 2 SECONDS; AFTER WHICH THE CHANNEL APPEARED TO CLOSE. I COULD NOT XMIT WHEN I PUSHED THE PUSH-TO-TALK SWITCH. HOWEVER; IT APPEARED THAT THERE WAS A 2-SECOND WINDOW IN WHICH XMISSION MIGHT HAVE BEEN POSSIBLE IMMEDIATELY AFTER THE PUSH-TO-TALK SWITCH WAS RELEASED. I CONCLUDED THAT 2-WAY RADIO COM WAS NO LONGER POSSIBLE. I CONTINUED TO XMIT MESSAGES; HOPING THAT SOMEONE COULD HEAR ME. I NEVER HEARD ANYTHING MORE ON THE RADIO. CONTRIBUTING FACTORS: THE TEMP AND DEWPOINT AT DPA ON THE GND WAS 33/31 DEGS F; STRADDLING FREEZING. PERHAPS THE TEMP CONTRIBUTED TO RADIO PROBS. I DECIDED TO RETURN TO THE DEP ARPT; DPA. I VECTORED MYSELF AROUND AND FLEW THE ILS 10 APCH. THE NAV RADIOS WORKED NORMALLY. I BROKE OUT AT ABOUT 1000 FT AGL AND LANDED ON RWY 10 WITHOUT A CLRNC AND WITHOUT INCIDENT. VERY QUICKLY; I DECIDED THAT THE TRANSCEIVER HAD FAILED. THIS MAY HAVE BEEN PREMATURE. THE FOLLOWING OPTIONS WERE NOT TRIED: USING THE SPEAKER INSTEAD OF THE HEAD SET. USING THE HAND MIKE INSTEAD OF THE MIKE ON THE HEADSET AND THE PUSH-TO-TALK SWITCH ON THE YOKE. CHKING TO ENSURE THAT ALL PLUGS WERE INSERTED INTO THE JACKS. CHKING THE SELECTOR SWITCHES FOR THE RADIO ON THE CTL PANEL. CYCLING THE RADIOS. I DID NOT SET MY XPONDER PROPERLY TO INDICATE A RADIO PROB (7600). I DID NOT CIRCLE THE ARPT TO DETERMINE THE TFC BEFORE LNDG. FACTORS AFFECTING THE QUALITY OF HUMAN PERFORMANCE: I WAS NOT FAMILIAR WITH THE PROPER PROCS TO FOLLOW DURING A LOSS OF 2-WAY RADIO COM. I HAVE SINCE REVIEWED THE FOLLOWING: 2-WAY RADIO COM FAILURE; XPONDER OP DURING 2- WAY RADIO COM FAILURE; RE-ESTABLISHING RADIO CONTACT; COM WITH TWR WHEN ACFT XMITTER OR RECEIVER OR BOTH ARE INOP. ARTCC RADIO FREQ OUTAGE; TFC CTL LIGHT SIGNALS; AND TAXIING. FAR 91.185; IFR OPS. 2-WAY RADIO COM FAILURE. I DID NOT REMEMBER THE LIGHT SIGNALS; SO I WAS NOT ABLE TO RESPOND PROMPTLY TO THE TWR'S USAGE OF LIGHT SIGNALS.