Confidence: Medium · Source: FCC ULS · As of 2026-09-14
KX4UM callsign genealogy
Currently held by Ulffe Whu, Gustavo E
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 KX4UM's current licensee, walking backwards.
The current licensee has not held any other callsign on record.
Successor callsigns
Callsigns held now by people who previously held KX4UM.
- Ulffe Whu, Gustavo EGAgranted 2019-10-04