Confidence: Medium · Source: FCC ULS · As of 2026-09-12
KC4JMB callsign genealogy
Currently held by Butler, John
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 KC4JMB's current licensee, walking backwards.
- Butler, JohnNCgranted 2026-07-28cancelled 2026-08-15
Successor callsigns
Callsigns held now by people who previously held KC4JMB.
No current licensee on record previously held this callsign.
All historical holders
Every license row we've seen with the callsign KC4JMB, oldest first.
- CASTILLO, GREGORIO A FL1989-03-28 → cancelled 2001-03-29
- Butler, John NC2026-08-15 active