Confidence: Medium · Source: FCC ULS · As of 2026-09-14
WA3TDU callsign genealogy
Currently held by ZIMMERMAN, DONALD C
The FCC publishes a previous_call_sign on
every amateur license — a self-link to the licensee's prior callsign.
Following those links produces the chain below.
Previous callsigns
Older callsigns held by WA3TDU's current licensee, walking backwards.
- Hartley, OwenCAgranted 2025-04-23cancelled 2025-06-03
Successor callsigns
Callsigns held now by people who previously held WA3TDU.
No current licensee on record previously held this callsign.
All historical holders
Every license row we've seen with the callsign WA3TDU, oldest first.
- ZIMMERMAN, DONALD C PA2007-05-07 → cancelled 2019-06-25
- Hartley Mr, Owen CA2025-06-03 active