ASR-7 RADAR SYS HAS TRACKING PROBS WHEN USING RWY 27L AND RWY 27R.

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AT ORD WE HAVE 2 RADAR SYS; AN ASR-9 AND AN ASR-7. THE ASR-7 IS A TEMPORARY BACKUP UNTIL ANOTHER ASR-9 CAN BE INSTALLED. TRACKING PROBS HAVE BEEN DOCUMENTED TO THE E OF ORD WHEN WE ARE USING RWYS 27L/R. THE PROB IS WHEN 2 ACFT GET SIDE BY SIDE; THE TARGETS JUMP AND AN ACCURATE POS OF THE ACFT IS HARD TO COME BY. THE FAA SOLUTION WAS TO REVERT TO THE ASR-7 WHEN RWY 27L/R WERE IN USE AND THE WX WAS IFR. TODAY WE HAD NUMEROUS INCIDENTS WHERE TARGETS DISAPPEARED OR JUMPED TO EACH OTHER WHEN THEY WERE SIDE BY SIDE ON RWYS 27L/R. WHEN THE WX IS IFR AND WE ARE FORCED TO USE THE RWY 27'S; OUR ARR RATE IS REDUCED ALMOST 20 PERCENT. NOW THE SAFETY FACTOR. WHEN IT IS IFR AND PARALLEL APCHS ARE BEING USED; MONITORS ARE NEEDED TO ASSURE ACFT DON'T VIOLATE THE NO TRANSGRESSION ZONE BTWN THE RWYS. WITH THESE TARGETS JUMPING AROUND; AN ACTUAL POS IS HARD TO PIN DOWN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THIS IS AN INTERMITTENT PROB. IT OCCURS NE OF THE ARPT AND ALSO TO SOME DEG; TO THE S. IT ONLY OCCURS WITH THE ASR-7 RADAR SYS. RPTR DOES NOT KNOW IF A UCR HAS BEEN FILED OR NOT. PROB HAS BEEN ONGOING FOR SOME TIME. THE PLAN IS TO REPLACE THEIR RADAR SYS WITH ASR-9'S WHENEVER ALL THE PROBS ARE WORKED OUT. RPTR ALSO STATES THAT THE ASR-9 RADAR IS IMPROVING. THEY RECENTLY DID SOME SOFTWARE WORK THAT HAS IMPROVED THE PRESENTATION.