Propagation & Band Conditions

HF propagation is a moving target — the ionosphere depends on time of day, season, sunspot cycle, geomagnetic storms, and local time at both ends of a path. The tools here range from "classical prediction" (VOACAP) to "live observation networks" (PSK Reporter, WSPRnet, RBN) that let you see exactly where your signal is being heard right now. Cross-link with Ham Digital Modes, Ham Logging, Ham Contesting, SDR Software.

Classical propagation prediction

• ★ VOACAP — Voice of America Coverage Analysis Program; HF propagation prediction model from the 1980s, still the gold standard. NTIA ITS released the source; Pat Pattle G3PLX wrote the free Windows GUI. Predicts Maximum Usable Frequency (MUF), Lowest Usable Frequency (LUF), expected SNR per band per hour. Free.
  • https://www.voacap.com
• VOACAP Online (G3PLX) — web version; free; the modern way to use VOACAP. Just enter two locations, get heat-mapped predictions per band per UTC hour.
• ICEPAC / REC533 — alternative HF models; less popular than VOACAP.
• Proppy (G0KYA) — VOACAP-based mobile app; closed; free; pretty UI.
• DR2W — older Windows propagation app; sunset.
• HamCAP — closed Windows app from VE3NEA; integrates with DXLab.

Real-time spot networks (live propagation)

• ★ PSK Reporter — Phil Gladstone N1DQ; the de-facto live FT8 / FT4 / PSK / RTTY heard-by map. Every WSJT-X / Fldigi station that opts in reports every decode; the database aggregates. Within seconds of you transmitting, every station that decoded you appears as a pin on the map. The single most useful real-time propagation indicator in the hobby. Free.
  • https://pskreporter.info
• ★ WSPRnet — WSPR (Weak Signal Propagation Reporter) network; continuously running propagation beacons worldwide on every HF band. Anyone running WSJT-X with WSPR mode contributes; the database is queryable. Free.
  • https://wsprnet.org
• ★ Reverse Beacon Network (RBN) — see Ham Contesting; CW Skimmer-fed live spotting of who's calling CQ where. Free; telnet feed.
• DX Cluster (DX Spider, AR-Cluster, CC Cluster) — older spot networks; mostly fed from RBN nowadays.
• HamSpots — newer aggregator; combines RBN + PSK Reporter + cluster.
• Hamspots.net / DXSummit / VK4HAT cluster — regional cluster mirrors.

Companion / visualization

• ★ GridTracker — see Ham Digital Modes; FT8 grid map + propagation visualization for WSJT-X. Closed; free.
• ★ JTAlert — Windows; alerts for needed states / countries / grids decoded by WSJT-X. Closed; free.
• DXKeeper / SpotCollector — DXLab Suite; cluster-aggregated spot UI for Windows.
• WSJT-X built-in PSKReporter feed — opt-in by default; recommended.

Band condition / solar indices

• ★ NOAA SWPC (Space Weather Prediction Center) — official US source for solar flux (SFI), A-index, K-index, geomagnetic storm warnings, solar X-ray flares. Free public data.
  • https://www.swpc.noaa.gov
• HamQSL.com Solar widget (N0NBH) — the "every ham website's sidebar widget"; quick SFI / A / K / sunspot summary. Free embed.
• Solar-Terrestrial Indices (STI) by HamCAP / DXLab — Windows companion data.
• Solarham (ve3en) — solar-cycle weather; great single-page forecast.
• SpaceWeather.com — public-friendly solar reporting; free.

VHF / 6 m / propagation specials

• DX Maps (EA6VQ) — maps of E-skip and tropospheric ducting on 6 m / 2 m / 70 cm; live data crowd-sourced. Free; subscription for premium features.
  • https://www.dxmaps.com
• APRS WX / Tropo — tropo prediction overlay on APRS maps.
• Hepburn Tropo Forecast — F1FRX's classic VHF tropo prediction maps; free.
• 6 m propagation watch — community Discord / Twitter / Mastodon channels; bursty cycle of activity.

Practical guidance

• VOACAP first, PSK Reporter second. Predict expected propagation, then verify with live data. They almost always disagree by 1–2 bands' worth.
• MUF != "what works." Maximum Usable Frequency is the highest one-hop F2 propagation; 5–15% below MUF is where real signals live (the FOT — Frequency of Optimum Transmission).
• K-index ≥ 4 = bad day. Geomagnetic storms wipe out HF propagation, especially at high latitudes. K=0–2 is great; K=3 is okay; K≥5 is "go work 6 m or take a nap."
• A-index is the daily summary of K-index; A < 10 is calm.
• Solar flux index (SFI). SFI > 150 = excellent ionospheric ionization, 10/15/20 m wide open. SFI < 70 = solar minimum, only 40/80/160 m work reliably.
• Operate the bands you can. During solar minimum, 80/40/30 m night-time DX; during solar max, 17/15/12/10/6 m daytime DX. The sunspot cycle (~11 years) is the master variable.
• Run WSPR continuously as your antenna's coverage map. A few watts on WSPR for a week paints exactly where your signal lands worldwide; tells you more about your antenna than any modeling.
• PSK Reporter + WSJT-X auto-feed is opt-in but recommended; everyone benefits when everyone shares decodes.

License / pricing notes

• VOACAP / Proppy / WSPRnet / PSK Reporter / RBN / DX Maps / HamQSL / SWPC — free.
• GridTracker / JTAlert / SpotCollector / DXKeeper — closed, free.
• HamCAP — closed, free.
• DR2W — sunset.
• Commercial propagation services (PropQuest etc.) exist for shortwave broadcasters; ham hobbyists rarely need them.

Pick this if…

• Default propagation prediction: VOACAP Online.
• Default live propagation map: PSK Reporter (FT8 era) + RBN (CW era) + WSPRnet (beacon).
• FT8 grid-square visualization: GridTracker.
• VHF tropo / E-skip: DX Maps + Hepburn Tropo.
• Solar weather glance: HamQSL solar widget on your dashboard.
• Long-term antenna evaluation: WSPR continuously for a week; map who hears you.
• Storm warnings: NOAA SWPC alerts (RSS or SMS).