What this is
Given a Maidenhead grid square, radio-weather rates how your receive and transmit conditions look, per band (160 m–6 m) and per mode (FT8, FT4, CW, SSB, …), right now and hour-by-hour out about a week, alongside a layered world map and a physical signal-path diagram.
It is an area-conditions tool. The headline question is "from my grid, how is my Rx and how is my Tx, per band and mode?" For the path loss to one specific station you want a VOACAP/ITU-R P.533 point-to-point engine, which this is not. It is a heuristic built on live public data, and every rating is explainable from the named inputs below.
Receive vs. transmit
Propagation is reciprocal: the ionospheric path treats your signal the same in both directions. What differs is the noise floor at the listening end.
- Rx is gated by your local noise: the galactic, atmospheric (lightning) and man-made noise at your station (ITU-R P.372). A noisy urban site hears far less than a quiet rural one on the identical path.
- Tx assumes the DX hears you at a quiet site, so it is propagation-limited only. This is why a city station can often be heard far away yet struggle to hear the same stations back.
For each band/mode we estimate a signal-to-noise ratio in a 2.5 kHz reference bandwidth and compare it to that mode's required SNR (the WSJT-X / VOACAP convention). The margin maps to a rating tier: Excellent → Good → Fair → Marginal → Poor → Closed.
Data sources
All public and key-free. If one upstream is down, the feature it feeds turns off and the rest of the page still renders.
| Source | What it is | How we use it |
|---|---|---|
| KC2G | Real-time MUF(3000 km) & foF2 from the GIRO ionosonde network, interpolated to a map. | The live MUF/foF2 anchor at your grid; everything else adjusts it. |
| NOAA SWPC | F10.7 solar flux, planetary Kp (observed + 3-hourly forecast), Ap, and the 45-day F10.7/Ap forecast. | Projects the anchor forward and drives the week-ahead axis and geomagnetic response. |
| NOAA SWPC solar cycle | Monthly observed & smoothed sunspot number back to 1749, plus SWPC's smoothed-SSN prediction with uncertainty for the rest of the cycle. | The 11-year cycle context behind today's number: onset, peak and phase, and the curve under the solar strip. |
| NOAA OVATION | Auroral-oval precipitation model (probability grid). | Map layer, a direct Rx penalty when the oval is overhead/poleward, and the auroral path-crossing in the directional model. |
| NOAA D-RAP | D-Region Absorption Prediction: global grid of the highest absorbed HF frequency. | Per-hop absorption (f_abs/f)^1.5 (the DRAP2 scaling law) that closes the affected bands during auroral, polar-cap and flare blackouts. Map + signal-path layer. |
| NOAA GOES | X-ray flux (live solar-flare detection). | An M/X-class flare drives a sunlit-side shortwave fadeout in real time, scoped by the subsolar geometry. |
| NOAA RTSW | Real-time L1 solar wind (operational spacecraft feed): IMF Bz and speed. | Southward Bz raises the near-term geomagnetic outlook hours before it reaches the Kp index. |
| NOAA GloTEC | Assimilative ionosphere: total electron content, NmF2, hmF2. | Blended into the MUF anchor where ionosondes are sparse (oceans, high latitudes); supplies the layer height along the signal path. Map layer. |
| WSPR.live | Observed WSPR beacon decodes (non-commercial use only). | Recent reception near you confirms which bands are open. It is a capped nudge, since silence isn't proof of closure. |
| VIIRS night-lights | 2024 annual nighttime-lights composite (OpenLandMap / VNL, calibrated radiance). | Light pollution proxies urbanization, so we pre-select your local-noise environment (P.372 category) from the grid. |
| Skyfield | Astronomical ephemeris (DE421). | Subsolar point, solar elevation and the grayline, everywhere day/night matters. |
| global-land-mask | Coastline land/sea mask, sampled to a committed 0.1° raster. | Land vs. sea under the signal path; sea reflections are far lower-loss over multi-hop paths. |
| ETOPO 2022 | Global relief / elevation model (NOAA NCEI), decimated to a compact 0.1° raster. | The ground-elevation silhouette beneath the signal path, so mountains and oceans along the bearing are visible. |
Methodology
Maximum usable frequency
The MUF is anchored to live KC2G at the current hour, then projected by solar elevation and the SWPC F10.7 forecast, so "now" matches observed reality and the forecast tracks the daily flux/Ap outlook. Where ionosondes are sparse, GloTEC's NmF2→foF2 is blended in by distance to the nearest sonde, sharpening otherwise-thin regions.
Sunspots & the 11-year cycle
Sunspots track the Sun's ~11-year activity cycle, and more of them means a more ionized F2 layer and a higher MUF, so the upper-HF bands (10/12/15 m) open more often and reach farther. The headline SSN is derived from the live F10.7 flux, but a bare number is ambiguous: 110 is strong near a minimum and weak near a maximum. The strip plots the current cycle's smoothed sunspot curve (observed, then SWPC's prediction with its uncertainty band) and marks where we are now and the cycle peak, so today's value reads against its phase (rising, near maximum, or declining). The cycle's onset and peak are detected from the smoothed series; the same phase framing tints the SSN chip relative to this cycle's min→peak range. Higher sunspot numbers also deepen daytime D-layer absorption on the low bands, which the model already folds into the ratings.
Noise floor
ITU-R P.372 combines the galactic background, atmospheric noise (lightning QRN) and man-made noise by environment (quiet-rural → rural → residential → city). This is the only thing separating the Rx and Tx ratings. The local-noise picker shows each environment's S-meter reading and dBm floor.
Nowcasts
Live conditions drive the ratings, not just the map. D-RAP absorption, OVATION overhead and GOES
flares add absorption; solar-wind Bz raises the near-term effective Kp; WSPR decodes boost a band's
confidence. Each relaxes toward the Kp/climatology forecast over time:
recency = exp(−h/6), and a faster exp(−h/2) for transient flares and spots.
Direction
You can aim the path at any azimuth (type it in or click/drag the compass rose) and the heading draws as a great-circle line on the map, with a pin on your DX grid. With an azimuth set, every rating is for a path aimed that way: the band cells, the 7-day timeline, the detail panel and the signal path. The ionosphere is sampled along every bearing (every 10° around the compass, every 250 km out to 11,000 km): foF2, any sporadic-E, D-RAP absorption and geomagnetic latitude at each point. A rated path is then judged hop by hop where it reflects: the weakest hop sets the path MUF, D-layer absorption and D-RAP are charged per hop using that point's own sun elevation (so a night-side station aiming into daylight pays for it), the auroral loss is the product of the per-hop oval crossings from each hour's Kp, and a sporadic-E path needs Es at every Es hop. The compass rose is the same computation run once per bearing, so a wedge is exactly what the band cell would show aimed there. The off-QTH nowcast terms relax toward the QTH values over the forecast like the other nowcasts. With no azimuth the ratings are omnidirectional: the best reachable first-hop direction for foF2 and sporadic-E, the QTH for aurora and absorption.
Signal path
The signal-path view unrolls a slice of the Earth along your chosen bearing using real ray geometry,
not stylized arcs. Hop distance for a takeoff angle Δ on a spherical Earth is
θ = 90°−Δ−asin(R·cosΔ/(R+h)), hop 2Rθ; the reflection cut-off comes
from the secant law f ≤ foF2·sec φ, which sets the skip zone (or NVIS when
f ≤ foF2). Layer height and foF2 vary along the path from the
live profile, each hop reflects at the local height, and rays above the local MUF escape to space.
Overlaid: daylight vs. darkness and the grayline; land vs. sea under each reflection; D-layer
absorption; the auroral-oval crossing; the E layer (and sporadic-E on 10/6 m, when present); and
ticks for how far each mode still decodes (the band SNR fades a few dB per hop).
Limitations
- It is a broad, qualitative indication of area conditions. For a specific circuit use VOACAP/ITU-R P.533.
- Along-path samples are taken now; for forecast hours the off-QTH ionosphere relaxes toward the QTH projection rather than being forecast point by point.
- Sporadic-E is shown as a possibility on the high bands, never forecast; it is too local and short-lived to call.
- In look-back replay the heatmap and ratings are historical, but the map overlays are still served live.
- Times are shown in your browser's local timezone ("when can I operate"), not grid mean time.
Credits
Data courtesy of KC2G / GIRO, NOAA SWPC, NOAA/EOG VIIRS, WSPR.live, and the Skyfield project. Free to use, no API keys. 73.