SPD DEV BY ACR ON CLBOUT REDUCING SEPARATION.

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WE WERE FOLLOWING A COMPANY SHORTS SD3-60 ON OUR CLB AFTER DEPARTING SAN JUAN'S LUIS MUNOZ MARIN INTL ARPT. WE HAD THE COMPANY IN SIGHT AND ON TCASII AND WE WERE GIVEN A SPD RESTR OF 160 KTS OR LESS. WE ASSUMED THAT THIS RESTR WAS ONLY FOR CLBOUT; SINCE WE WERE CLBING IN SIMILAR ACFT AND THEREFORE HAD SIMILAR SPDS. AS WE LEVELED OFF; WE SET OUR NORMAL CRUISE PWR WHICH YIELDED ABOUT 180 KTS. WE ADVISED ATC THAT WE HAD COMPANY IN SIGHT TWICE BUT THERE WAS NO RESPONSE. AGAIN WE CALLED ATC ADVISING THEM THAT WE MIGHT OVERTAKE COMPANY AND AGAIN; NO RESPONSE. LATER; ATC ASKED US OUR SPD. SINCE IT WAS HIGHER THAN WHAT HE EXPECTED AND THE SEPARATION DECREASED; HE GAVE US A LOWER ALT. AFTER OUR DSCNT; HE ASKED US TO CALL THE SAN JUAN CERAP. ON THIS CALL WE FOUND OUT THAT THE SAN JUAN CERAP WAS EXPERIENCING PROBS WITH THEIR COMS LINKAGE; AND THE CTLR WAS HANDLING SEVERAL FREQS AT A TIME. THIS OVERLOADED CONDITION MAY HAVE PREVENTED THE CTLR OF BEING CLR ENOUGH THEREFORE LEADING US TO MISUNDERSTAND HIS INSTRUCTIONS.