Data Sources
FCC Universal Licensing System (ULS)
All license data on CallSignLookup comes from the FCC's Universal Licensing System public data files. The FCC makes the full ULS database available as free bulk downloads covering every radio service category:
https://www.fcc.gov/uls/transactions/daily-weekly.html
The FCC publishes both daily incremental files and full weekly snapshots every Saturday. We ingest the full weekly snapshots across all major service categories, covering over 4 million license records.
File Structure
Each service dataset is a directory of pipe-delimited .dat files. The core files used across all services are:
| File | Contents |
|---|---|
| HD.dat | Main license record — call sign, status, grant/expiration dates, radio service code |
| EN.dat | Entity/licensee record — name, address, city, state, ZIP, FCC Registration Number, entity type |
| AM.dat | Amateur-specific record — operator class, call sign group, trustee, previous call sign (amateur radio only) |
| SH.dat | Ship station record — vessel name, vessel class, vessel type, MMSI number (maritime services only) |
Records in HD, EN, AM, and SH are joined on a common record_key to build a complete licensee profile.
Update Frequency
The FCC publishes daily incremental updates and a full weekly snapshot every Saturday. We ingest the full weekly snapshots. The date of the last completed update is shown in the footer of every page.
License Status Codes
| Code | Meaning |
|---|---|
| A | Active — license is valid and in good standing |
| C | Cancelled — voluntarily cancelled by the licensee |
| E | Expired — past expiration date; may still be renewable within the grace period |
| T | Terminated — administratively terminated by the FCC |
| P | Pending — application submitted, awaiting FCC action |
Amateur Radio Operator Classes
| Code | Class | Notes |
|---|---|---|
| E | Extra | Highest class; all privileges on all amateur bands |
| A | Advanced | Legacy class; no longer issued but remains valid |
| G | General | Intermediate; access to most HF bands worldwide |
| T | Technician | Entry level; VHF/UHF focus, limited HF privileges |
| N | Novice | Legacy class; no longer issued |
| P | Technician Plus | Legacy Technician variant; no longer issued |
Accuracy & Limitations
- Data may lag behind the official FCC database by up to one week
- Address data is self-reported by licensees to the FCC and may not be current
- Some less common service categories may not be fully indexed
- For official real-time verification, use the FCC ULS License Search