Narrative:

Small aircraft X IFR 60 swbnd from 81B to con reporter level at 6000' 25 mi northwest of pwm. Air carrier Y 30 mi northwest pwm assigned 3000' descending from 8000'. This air carrier Y was eastbound being vectored for ILS runway 11 approach. I expected through projections that air carrier Y would pass 4 mi north of small aircraft X. The air carrier Y started down out of 7000. However, before air carrier Y crossed north of small aircraft X I lost radar on small aircraft X. Not being able to ensure sep I stopped air carrier Y at 7000'. He almost descended below 7000'. I kept air carrier Y at 7000' until north of centerline runway 11 and had him make a left 360 degree turn for descent. No loss of sep occurred, but easily could have. Reestablished radar 10 mi from where I originally lost the small aircraft X. Solution: replace radar. Callback conversation with reporter revealed the following: reporter stated this incident happened in a known area of poor radar coverage. A hotel was built about 2 yrs ago. Due to a typographical error, a 6 story hotel was erected 2000' from the radar antenna vs 20000'. This has created an area of non rdar coverage from bearing 230 through bearing 285, from ground to 9000'. Ucr was filed 1 1/2 yrs ago. Reporter was told they were going to get new ASR 9 radar to correct problem. ASR 9 has not been installed. FAA will not move radar antenna. There are 2 military bases within 20 mi that have ASR 8 and could be microwaved to pwm, which would give the facility better radar coverage and solve the problem. Analyst advised reporter to turn in a written formal suggestion to FAA.

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Original NASA ASRS Text

Title: LOSS OF RADAR CONTACT REVERTED TO VERTICAL SEPARATION. SITUATION: LACK OF RADAR COVERAGE DUE TO OBSTRUCTION TO RADAR ANTENNA.

Narrative: SMA X IFR 60 SWBND FROM 81B TO CON RPTR LEVEL AT 6000' 25 MI NW OF PWM. ACR Y 30 MI NW PWM ASSIGNED 3000' DSNDING FROM 8000'. THIS ACR Y WAS EBND BEING VECTORED FOR ILS RWY 11 APCH. I EXPECTED THROUGH PROJECTIONS THAT ACR Y WOULD PASS 4 MI N OF SMA X. THE ACR Y STARTED DOWN OUT OF 7000. HOWEVER, BEFORE ACR Y CROSSED N OF SMA X I LOST RADAR ON SMA X. NOT BEING ABLE TO ENSURE SEP I STOPPED ACR Y AT 7000'. HE ALMOST DSNDED BELOW 7000'. I KEPT ACR Y AT 7000' UNTIL N OF CENTERLINE RWY 11 AND HAD HIM MAKE A LEFT 360 DEG TURN FOR DSNT. NO LOSS OF SEP OCCURRED, BUT EASILY COULD HAVE. REESTABLISHED RADAR 10 MI FROM WHERE I ORIGINALLY LOST THE SMA X. SOLUTION: REPLACE RADAR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATED THIS INCIDENT HAPPENED IN A KNOWN AREA OF POOR RADAR COVERAGE. A HOTEL WAS BUILT ABOUT 2 YRS AGO. DUE TO A TYPOGRAPHICAL ERROR, A 6 STORY HOTEL WAS ERECTED 2000' FROM THE RADAR ANTENNA VS 20000'. THIS HAS CREATED AN AREA OF NON RDAR COVERAGE FROM BEARING 230 THROUGH BEARING 285, FROM GND TO 9000'. UCR WAS FILED 1 1/2 YRS AGO. RPTR WAS TOLD THEY WERE GOING TO GET NEW ASR 9 RADAR TO CORRECT PROB. ASR 9 HAS NOT BEEN INSTALLED. FAA WILL NOT MOVE RADAR ANTENNA. THERE ARE 2 MIL BASES WITHIN 20 MI THAT HAVE ASR 8 AND COULD BE MICROWAVED TO PWM, WHICH WOULD GIVE THE FAC BETTER RADAR COVERAGE AND SOLVE THE PROB. ANALYST ADVISED RPTR TO TURN IN A WRITTEN FORMAL SUGGESTION TO FAA.

Data retrieved from NASA's ASRS site as of July 2007 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.