DURING VECTORS TO PARALLEL RWYS; DAY APCH CTLR HAS FREQ STEPPED ON CAUSING ONE OF THE TWO DC9 CARGO ACFT TO OVER SHOOT BOTH RWYS.

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WE WERE BEING VECTORED FOR AN ILS APCH TO RWY 4L AT ILN IN VMC CONDITIONS. SIMULTANEOUS APCHES WERE BEING CONDUCTED TO RWY 4R. ON BASE; A CLRNC FOR A FINAL TURN TO INTERCEPT AND APCH WAS GIVEN BY ATC; HOWEVER; THE FIRST PART OF THE XMISSION WAS 'STEPPED ON' AND NO FLT NUMBER WAS HEARD. MY CAPT IMMEDIATELY XMITTED 'BLOCKED'; TO INDICATE THAT ATC'S LAST XMISSION WAS NOT RECEIVED. APCH CTL XMITTED TWO OR THREE ADDITIONAL CLEARANCES TO OTHER ACFT; TO INCLUDE A TURN ON AND APCH FOR PARALLEL RWY TFC BEFORE I COULD XMIT 'WHAT WOULD YOU LIKE FLT ACR X TO DO?' AT THIS POINT WE HAD ALREADY CROSSED THE EXTENDED CENTERLINE OF RWY 4L. APCH REPLIED WITH 'I ALREADY CLRED YOU FOR THE APCH; TURN LEFT TO 030 DEGS TO INTERCEPT THE LOC FOR RWY 4L! 'PARALLEL TFC WAS BEGINNING ITS TURN TO FINAL. (FROM MY PERSPECTIVE; FACING US; BUT HIGHER AND L OF US). MY CAPT (FLYING) MADE AN IMMEDIATE TURN L TO INTERCEPT RWY 4L; USING UP TO A 45 DEG BANK; BECAUSE HE BELIEVED WE WERE GETTING TOO CLOSE TO THE ONCOMING ACFT. I CONCURRED. OUR TURN TOOK US BEYOND THE EXTENDED CENTERLINE OF RWY 4R. THE PARALLEL ACFT CALLED ATC CONCERNED THAT WE HAD FLOWN UNDER THEM. MY ESTIMATE IS THAT WE WERE NEVER CLOSER THAN 500-1000 FT HORIZONTAL AND 300-500 FT VERTICAL. HARD TO TELL ACCURATELY AT NIGHT. SOLUTION; I SUPPOSE WE COULD HAVE ASSUMED THE 'BLOCKED' CLEARANCE WAS FOR US; AND MADE THE TURN TO FINAL. BUT WE BELIEVED THERE WAS SUFFICIENT TIME TO CONFIRM; NOT ANTICIPATING ATC NOT REPEATING THE CLRNC INTENDED FOR US. WHEN WE FINALLY RECEIVED OUR APCH CLRNC; IM NOT SURE WHAT OTHER OPTIONS WERE AVAILABLE. WE COMPLIED WITH THE TURN BACK TO INTERCEPT BUT MODIFIED (STEEP TURN) IN ORDER TO AVOID ANY CONFLICT WITH OTHER ACFT. ADDITIONALLY; THERE WAS ANOTHER ACFT ON AN EXTENDED STRAIGHT IN FOR RWY 4R; AND I BELIEVE OTHER TFC BEING VECTORED ON DOWNWIND FOR RWY 4R. SUPPLEMENTAL INFO FROM ACN 494930: OUR COMPANY WILL NOT BUY US TCAS. WE CONTINUED LAST ASSIGNED HDG; FINALLY GETTING TO ASK ATC WHAT WE SHOULD DO. WE WERE WELL PAST OUR LOC NOW. ATC ISSUED A TURN TO INTERCEPT LOC WITH APCH CLRNC AND SEEMED SURPRISED WE WEREN'T ON THE LOC ALREADY. NOW SAW TFC MAKING HIS TURN ONTO PARALLEL LOC COMING AT US. I STOPPED TURN THINKING WE WERE TURNING INTO EACH OTHER EXPECTING TO HAVE TO MAKE A REVERSE TURN BEHIND HIM. WINGS LEVEL SAW WE HAD A COUPLE OF HUNDRED FT VERTICAL SEPARATION BELOW HIM (MAYBE). ATC RESTATED CLRNC TO TURN TOWARD LOC WHILE FO URGED THAT WE DO THE SAME. NO TIME TO ASK IF MY 'DIVERSIONARY' PATH BEHIND TFC WAS CLR SO DROPPED 300 FT BELOW ASSIGNED INTERCEPT ALT AND CONTINUED HARD TURN BELOW TFC TO JOIN LOC. LOST SIGHT OF TFC ABOVE US BRIEFLY IN TURN. BY NOW WE WERE IN THE PARALLEL LOC COURSE. REMAINING APCH AND LNDG WERE NORMAL.