VFR aircraft going through tpa airspace level at 3500 ft and receiving TA's has mode C altitude jump...

Attributes
ACN	230434
Time
Date	199301
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : srq
State Reference	FL
Altitude	msl bound lower : 3500 msl bound upper : 6500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : tpa tower : mdw
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 4 controller radar : 11
ASRS Report	230434
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

Aircraft was tracking northwest to southeast 5 mi east of srq VOR level at 3500 ft. ARTS data block kept going to 6500 ft. ARTS went back and forth between 3500 and 6500 for about 20 mi of aircraft's flight. We had more ARTS problems than normal on this day with both the tpa ASR 8 and the sarasota digital system. We were too busy to log each occurrence.

Original NASA ASRS Text

Title: VFR ACFT GOING THROUGH TPA AIRSPACE LEVEL AT 3500 FT AND RECEIVING TA'S HAS MODE C ALT JUMP.

Narrative: ACFT WAS TRACKING NW TO SE 5 MI E OF SRQ VOR LEVEL AT 3500 FT. ARTS DATA BLOCK KEPT GOING TO 6500 FT. ARTS WENT BACK AND FORTH BTWN 3500 AND 6500 FOR ABOUT 20 MI OF ACFT'S FLT. WE HAD MORE ARTS PROBS THAN NORMAL ON THIS DAY WITH BOTH THE TPA ASR 8 AND THE SARASOTA DIGITAL SYS. WE WERE TOO BUSY TO LOG EACH OCCURRENCE.

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.