As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON THE FIRST FLIGHT OF THE DAY OUTBOUND ON FLIGHT 3529 TCAS FAILED. AIR RETURN TO MSP. MAINTENANCE REMOVED & REPLACED LOWER TCAS ANT. P/N OFF/ON 622-8973-001. S/N OFF/7796. S/N ON 11P9T. TCAS OP CHECKS GOOD IAW RJ-85 M/M CHAP 34. REMOVED FROM DMR. MXC NOTIFIED.