Callsign Lookup & Data Files

Every decode is enriched with its DXCC entity, CQ zone, continent and grid so the engine can colour rows, evaluate marathon/zone targets, and flag LoTW users. This page explains the lookup and the data files behind it.

The lookup chain

For each callsign, the app resolves the entity in priority order:

1. In-memory cache — a fast cache of recent lookups.
2. Invalid operations — known bogus/illegal operations are rejected.
3. Club Log callsign exceptions — per-call overrides (e.g. a call operating from a different entity). Highest confidence.
4. Country data — the primary entity/zone source (longest-prefix match, plus exact-call overrides).
5. Prefix fallback — longest-first prefix scan.

The result includes the entity, CQ zone, continent and grid (noting whether the grid was provided, cached or guessed), plus a LoTW flag.

Data files

The app relies on a few reference data sets:

• Country data files (from Club Log and country-files.com) — DXCC entities, prefixes, exact-call and zone overrides, and invalid operations.
• CQ-zone geometry (bundled) — used to find the CQ zone from a grid.
• The LoTW user list (from ARRL LoTW) — which callsigns use LoTW (the • indicator + LoTW filter).
• A local cache of resolved lookups and callsign→grid fallbacks, for speed.

Keeping data current

From the Tools menu:

• Update DXCC Info → refreshes the DXCC country data from Club Log.
• Update country and region files → refreshes the country file from country-files.com.
• Update LoTW Info → refreshes the LoTW user list.

These can also be refreshed together in one pass during update flows.

CQ-zone resolution

To find a CQ zone from a grid, the app converts the Maidenhead locator to latitude/longitude and tests it against the CQ-zone areas (with a nearest-zone fallback near borders). This is what makes Wanted CQ Zone(s) targeting work even when the decode doesn't explicitly state a zone.

Caching and performance

• Lookups are kept in memory and persisted to a local cache, flushed on exit.
• Prefix tables are pre-indexed for fast longest-prefix matching.
• Grid/coordinate helpers are cached, so heavy band openings don't bog down the UI.