RADIO COM PROB ALMOST CAUSES LOSS OF SEPARATION.

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ON OUR INITIAL DSCNT INTO PHL; WE WERE STEPPED DOWN TO FL250. WE WERE IN CONTACT WITH ZOB ON FREQ 119.92. ABOUT 5 MINS EARLIER WE HAD HEARD SOME TAXI INSTRUCTIONS ON THAT FREQ AS WELL AS SOME VECTORING FROM AN APCH CTL. WE ASKED ZOB IF HE COULD STILL READ US; JUST TO MAKE SURE THAT OUR RADIO WAS STILL ON THE CORRECT FREQ. HE RESPONDED AND ALSO MENTIONED THAT THEY HAVE BEEN EXPERIENCING SOME SIMILAR PROBS WITH THAT FREQ. SO OUT OF THE BLUE; ZOB ASKED US TO DSND TO FL240 AND EXPEDITE DSCNT; WHICH WE DID. HE LATER SENT US TO ZNY ON 132.2. EVEN THAT XMISSION WAS HALF GARBLED AT THAT TIME. WE LATER FOUND OUT THAT ANOTHER ACFT AT FL250 WAS HDG FOR THE SAME VOR AS WE WERE. IN A PHONE CONVERSATION WITH AN ATC SUPVR; THE 2 ACFT IN QUESTION COMPLIED FULLY WITH ATC SEPARATION GUIDELINES. HOWEVER; THE POTENTIAL WAS THERE; BECAUSE THEY COULD NOT ESTABLISH RADIO COM WITH THE OTHER ACFT EITHER. APPARENTLY ZOB HAD ATTEMPTED TO CALL US TWICE BEFORE AND MADE CONTACT ON THE THIRD TRY. I AM NOT REALLY SURE WHY WE DID NOT HEAR THE FIRST 2 RADIO XMISSIONS; BUT I SUSPECT THERE MIGHT BE PROBS WITH THAT RADIO FREQ 119.92.