SF340B ACFT HAD COM FAILURE ON INITIAL CLB. FLC SQUAWKED 7600; RETURNED TO ARPT XMITTING IN THE BLIND; FLEW A LOW PASS DOWN THE LNDG RWY AND LOOKED FOR A LIGHT FROM THE TWR; WHICH THEY DIDN'T SEE. LNDG WAS UNEVENTFUL AND POSTFLT DISCOVERED THE XMITTER RECEIVER BRACKET HAD COME LOOSE; ALLOWING THE UNIT TO DISCONNECT.

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ON OCT/XX/97 AT APPROX 400-500 FT AGL ON CLBOUT; I GOT SEVERE STATIC IN MY HEADSET FOR APPROX 2-3 SECONDS AND THEN COMPLETE SILENCE. MY FO TOLD ME HE HAD THE SAME THING HAPPEN TO HIM. WE LOST ALL COMS CAPABILITY WITH ATC -- XMISSION AND RECEPTION; AND WE ALSO LOST OUR INTERCOM IN THE COCKPIT. WE COULD STILL COMMUNICATE WITH THE FLT ATTENDANT AND THE PA SYS WAS STILL OPERATIONAL. WE ELECTED TO RETURN TO CMI INSTEAD OF CONTINUING ON TO ORD. WE SQUAWKED 7600 IN THE XPONDER AND TURNED AROUND TO RETURN TO CMI. I DID NOT KNOW IF WE HAD LOST XMISSION SO I BROADCAST OUR INTENTIONS IN THE BLIND ON CMI DEP FREQ. WE ENTERED A L DOWNWIND FOR RWY 32L. I CONTINUED TO BROADCAST IN THE BLIND WHILE MY FO FLEW THE AIRPLANE. WE MADE A L PATTERN AND CONFIGURED THE ACFT FOR LNDG. WE THEN MADE A LOW PASS DOWN RWY 32L WITH THE GEAR AND FLAPS DOWN. WE WERE LOOKING AT THE TWR FOR LIGHT GUN SIGNALS BUT WE DID NOT SEE ANY. WE EXECUTED A GAR; CLEANED UP THE ACFT; AND FLEW A L PATTERN BACK TO RWY 32L. I TOLD THE FO THAT WE WOULD LAND ON THIS APCH WITH OR WITHOUT LIGHT GUN SIGNALS. WE LANDED THE ACFT WITHOUT INCIDENCE AND TAXIED BACK TO OUR RAMP AREA. WE NEVER DID SEE ANY LIGHT GUN SIGNALS FROM THE TWR. AFTER DEPLANING THE PAX; I CALLED THE TWR AND EXPLAINED WHAT HAD HAPPENED. THEY TOLD ME THEY RECEIVED THE 7600 SQUAWK AND HAD GIVEN US LIGHT GUN SIGNALS. WE HAD MAINT COME OUT TO THE ACFT AND THEY FOUND THAT A BRACKET WHICH HOLDS THE COMS XMITTER/RECEIVER IN PLACE HAD COME LOOSE ALLOWING THE UNIT TO DISCONNECT. THEY PLUGGED IT BACK IN AND RESECURED IT AND EVERYTHING WORKED FINE AGAIN. WE DEPARTED FOR CHICAGO AT XX31 AND THE FLT WAS UNEVENTFUL. ONE NOTE TO ADD: WE DID NOT LOSE OUR NAV CAPABILITIES OR XPONDER; ONLY OUR COMS.