TRACON ARTS radar does a data tag swap which causes a less than standard separation occurrence.

Attributes
ACN	250712
Time
Date	199309
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : pdx
State Reference	OR
Altitude	msl bound lower : 2300 msl bound upper : 3000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pdx
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air taxi
Make Model Name	Small Transport
Flight Phase	climbout : intermediate altitude
Route In Use	departure sid : sid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 13000 flight time type : 1000
ASRS Report	250712
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action other
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 200 vertical : 700
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	Operational Error
Situations
ATC Facility	other physical facility

Narrative:

After taking off from runway 28R at pdx departure control issued a turn to 160 heading. We were already cleared to 9000 ft (this turn seemed reasonable account runway 28L was closed). Soon, 3 things happened at once: 1) we came on top of an overcast, 2) departure issued an urgent level-off at 3000 ft, 3) the TCASII gave an RA of descend-descend. We followed the TCASII command and observed the conflicting traffic -- which was the small transport which departed IFR just before we did. Apparently (learned from a series of later phone calls). Our radar tag attached itself to another jet departure about 8 mi in front of us -- the turn to 160 heading was really for him. The TCASII saved the day and a very alert controller was seconds behind the TCASII -- but probably would have been too late. I don't understand the technicalities, but contributing to the error was the fact that both aircraft (jets) had transponder codes a few digits apart. If transponder codes were assigned truly at random, the chances of my type of incident could be reduced. Maybe NASA could look into how transponder codes are assigned and find a method which takes advantage of true random assignments.

Original NASA ASRS Text

Title: TRACON ARTS RADAR DOES A DATA TAG SWAP WHICH CAUSES A LTSS OCCURRENCE.

Narrative: AFTER TAKING OFF FROM RWY 28R AT PDX DEP CTL ISSUED A TURN TO 160 HDG. WE WERE ALREADY CLRED TO 9000 FT (THIS TURN SEEMED REASONABLE ACCOUNT RWY 28L WAS CLOSED). SOON, 3 THINGS HAPPENED AT ONCE: 1) WE CAME ON TOP OF AN OVCST, 2) DEP ISSUED AN URGENT LEVEL-OFF AT 3000 FT, 3) THE TCASII GAVE AN RA OF DSND-DSND. WE FOLLOWED THE TCASII COMMAND AND OBSERVED THE CONFLICTING TFC -- WHICH WAS THE SMT WHICH DEPARTED IFR JUST BEFORE WE DID. APPARENTLY (LEARNED FROM A SERIES OF LATER PHONE CALLS). OUR RADAR TAG ATTACHED ITSELF TO ANOTHER JET DEP ABOUT 8 MI IN FRONT OF US -- THE TURN TO 160 HDG WAS REALLY FOR HIM. THE TCASII SAVED THE DAY AND A VERY ALERT CTLR WAS SECONDS BEHIND THE TCASII -- BUT PROBABLY WOULD HAVE BEEN TOO LATE. I DON'T UNDERSTAND THE TECHNICALITIES, BUT CONTRIBUTING TO THE ERROR WAS THE FACT THAT BOTH ACFT (JETS) HAD XPONDER CODES A FEW DIGITS APART. IF XPONDER CODES WERE ASSIGNED TRULY AT RANDOM, THE CHANCES OF MY TYPE OF INCIDENT COULD BE REDUCED. MAYBE NASA COULD LOOK INTO HOW XPONDER CODES ARE ASSIGNED AND FIND A METHOD WHICH TAKES ADVANTAGE OF TRUE RANDOM ASSIGNMENTS.

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.