Public licensing data published by the U.S. Federal Communications Commission. Across the portal we currently load: Amateur (HA) ~660,000 active licenses; Microwave (CF / MG / MW / etc.) ~916,000 sites with their licensees; Land Mobile Private (Public Safety, Industrial) ~2.32 million; FCC Broadcast (FM / AM / TV) ~40,000 stations; and Maritime (Ship Radio Service + Coast Stations from the ULS Ship + Coast dumps). ULS is updated daily; we refresh weekly.

The longest-running maritime mobile net, on 14.300 MHz daily 1600 to 0200 UTC. Their published net schedule and operating procedures inform the HF nets table on the Maritime page.

The International Telecommunication Union defines and publishes the GMDSS distress + safety frequency plan (HF voice + DSC channels) that every maritime SSB and DSC radio is tuned to.

The U.S. Coast Guard publishes the US VHF marine channel allocation table and the operating schedules for the NMG (New Orleans) and NMC (Pt. Reyes) HF voice + weather-fax broadcasts.

NOAA's marine forecast offices and weather radio service publish the NAVTEX schedules and VHF Weather Radio channel assignments used by US coastal mariners.

Jim Reisert AD1C's canonical country-file used by every major ham logging package. We use the prefix aliases to resolve a callsign (K3DPT, WH6HGX, KL7AA, …) to its DXCC entity (United States, Hawaii, Alaska).

Paul Herrman N0NBH publishes a regularly-updated solar conditions widget that pre-digests NOAA Space Weather Prediction Center data into the per-band Good / Fair / Poor predictions hams actually use. We cache the feed server-side and refresh every ~30 minutes.

SWPC publishes its products as plain JSON: the OVATION aurora model (where the oval is right now), the planetary Kp index, the GOES X-ray flux (which we turn into a flare class and an HF radio-blackout level), and the solar wind magnetic field. We poll once every 5 minutes and cache it, so the numbers stay live without leaning on their servers. This is the same NOAA data the HamQSL widget pre-digests, read straight from the source.

The USGS publishes a real-time GeoJSON feed of earthquakes worldwide. We poll the magnitude 2.5+ past-day feed every couple of minutes and plot each quake sized by magnitude. Earthquakes are where emergency communications nets spin up, so it sits naturally next to the live activity.

The National Weather Service public API. We use the active-alert polygons (the tinted warning areas on the maps) and, for a QTH inside the US, the point forecast plus the nearest station's latest observation. Everything is cached server-side so we stay light on their service. US and territories only.

The AWC publishes airport surface observations (METAR) and the active AIRMET/SIGMET hazard areas (convection, turbulence, icing, IFR) as JSON. We poll the CONUS set every 10 minutes and plot the airports colored by flight category next to the live aircraft. US coverage.

The NDBC publishes the latest observations from moored buoys and coastal stations: wind, waves, pressure, air and water temperature. We pull the single latest-obs file every 10 minutes and plot each station colored by water temperature next to the live vessels.

Andrew Rodland KC2G publishes a global MUF(3000) map assimilated from real-time ionosonde soundings in the Global Ionosphere Radio Observatory (GIRO) / Lowell DIDBase. He provides the contour field as GeoJSON, which we cache and redraw every 15 minutes. The MUF tells you the highest frequency the ionosphere will currently support for a roughly 3000 km hop, so the contours show which HF bands are open where.

Dr. T.S. Kelso's CelesTrak publishes the NORAD two-line element sets we feed into our own SGP4 propagator to compute live amateur-satellite positions, ground tracks, and pass predictions. We poll the amateur group every few hours.

The community-run SatNOGS database publishes the active transmitter frequencies for amateur satellites. We look these up per bird to show the transponder and the Doppler-corrected frequencies on the satellite detail card; the Doppler shift itself comes from our own SGP4 range-rate calculation.

The Terrarium-format global elevation tiles (Mapzen / Tilezen, hosted on AWS Open Data, built from SRTM, ASTER, and national surveys) give us the ground elevation around a station. We decode a small block of tiles and walk radials with an earth-curvature correction to find the horizon angle in every direction; the propagation and satellite math on top of that is our own.

The ~30 deleted DXCC entities most active DXers worked before they came off the active list. Each carries the date of deletion and a short context paragraph. Hand-curated from ARRL's published DXCC rulebook and W4DXCC reference material.

1:110,000,000-scale world coastlines used for the grey-line globe visualization. Natural Earth is a free vector + raster map dataset maintained by the cartographic community.

When you type a city on the grey-line page, K3DPT looks it up through OpenStreetMap's free Nominatim geocoder. Repeat lookups are cached server-side so we stay well inside their usage policy.

Vector basemap tiles rendered by CARTO using OpenStreetMap data. Light theme chosen to keep the marker layer readable when many sites overlap.

Open-source vector map renderer (MapLibre, BSD-3) with a deck.gl WebGL layer for the marker overlays. Both are vendored locally, so your browser makes no third-party CDN calls when you load the map page.

Google Fonts serves the typeface. We don't track readers; the only third-party request your browser makes on a page load (besides the map's CARTO tiles) is for these font files.