Narrative:

Aircraft #1 calls for VFR advisories and is idented. Approximately 1 min later states he had a near midair. Aircraft #2 is handed off from bradley approach. I took to the frequency to ask aircraft #2 if he saw the other aircraft. He stated yes and that bdl approach never called it. I believe that proximity to long range surveillance radar sight caused the limited data block of aircraft #2 not to be displayed on sector 36 radar display.

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Original NASA ASRS Text

Title: ZBW CTLR DESCRIBED AN NMAC AT 5500 FT RPTED BY A VFR ACFT ON FREQ; INDICATING LACK OF DATA BLOCK INFO ON SECOND ACFT.

Narrative: ACFT #1 CALLS FOR VFR ADVISORIES AND IS IDENTED. APPROX 1 MIN LATER STATES HE HAD A NEAR MIDAIR. ACFT #2 IS HANDED OFF FROM BRADLEY APCH. I TOOK TO THE FREQ TO ASK ACFT #2 IF HE SAW THE OTHER ACFT. HE STATED YES AND THAT BDL APCH NEVER CALLED IT. I BELIEVE THAT PROX TO LONG RANGE SURVEILLANCE RADAR SIGHT CAUSED THE LIMITED DATA BLOCK OF ACFT #2 NOT TO BE DISPLAYED ON SECTOR 36 RADAR DISPLAY.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.