Confidence: Medium · Source: FCC ULS · As of 2026-09-14
W5TSU callsign genealogy
Currently held by Grennan, Mark T
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 W5TSU's current licensee, walking backwards.
- Grennan, Mark TOKgranted 2007-02-21cancelled 2014-03-22
Successor callsigns
Callsigns held now by people who previously held W5TSU.
No current licensee on record previously held this callsign.
All historical holders
Every license row we've seen with the callsign W5TSU, oldest first.
- STEINBECK, BERNARD R OK1989-07-18 → cancelled 2001-07-19
- Grennan, Mark T OK2024-01-17 active