Confidence: Medium · Source: FCC ULS · As of 2026-09-12
AC4ZM callsign genealogy
Currently held by Harms, Mark J
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 AC4ZM's current licensee, walking backwards.
- Harms, Mark JFLgranted 2011-03-25cancelled 2012-10-05
Successor callsigns
Callsigns held now by people who previously held AC4ZM.
No current licensee on record previously held this callsign.
All historical holders
Every license row we've seen with the callsign AC4ZM, oldest first.
- TINSMAN, WILLIAM F NC1993-01-26 → cancelled 2005-01-27
- Harms, Mark J FL2022-08-13 active