PropMap

Solar situation & radio impact

Loading solar wind and geomagnetic interpretation…

The planetary K-index (Kp) measures geomagnetic disturbance from 0 (quiet) to 9 (extreme storm) on a 3-hour cadence. Higher Kp usually degrades HF on polar/high-latitude paths, but can open rare 6m/2m aurora contacts. Solar flares are classed A–X by X-ray output, each letter roughly 10x the last — large M/X flares can cause a sudden daytime HF blackout lasting under an hour. Full scale reference: NOAA Space Weather Scales ↗

Grey line, right now

Grey line is the twilight band circling the Earth at sunrise and sunset. The D-layer — which absorbs HF signals during the day — collapses at dusk and hasn't reformed at dawn, so low bands like 40m and 80m can carry signals with unusually little loss. It's one of the best windows for long-distance DX, which is why your station's marker glows when it's near that line.

Band rankings

Working out the maximum usable frequency…

This ranking blends two things: which bands are typically open by day vs. night due to how the ionosphere's layers form and decay, and current geomagnetic activity (Kp), which degrades higher bands and polar paths when elevated. The MUF estimate comes from live solar flux, the season and the sun's height at your location; daytime absorption, grey line, Kp and flares are then factored in. It's a model, not a spot report — always cross-check against a real-time spotting network like PSK Reporter ↗ before calling CQ.

VHF & UHF conditions

HF skips off the ionosphere; VHF/UHF mostly doesn't. These bands ride on different physics — aurora, sporadic-E, and tropospheric ducting — so they get their own honest read here instead of being folded into the HF model above.

Aurora openings on 6m/2m ride the same Kp spike that hurts HF — a stable high-pressure system with a temperature inversion is what drives tropo ducting on 2m/70cm, so check a regional weather/pressure map rather than a space-weather feed for that one. Sporadic-E is a real seasonal pattern (short-lived ionized patches in the E-layer), strongest in northern-hemisphere summer, and opens 10m/6m/occasionally 2m unpredictably within that window — DXMaps ↗ tracks live Es openings.

Band reference

Path analyzer

Detecting your location…

Short path is the direct great-circle route to the DX station; long path is the same route the other way around the globe — sometimes open when the short path isn't, especially near grey line.

Plan my contact

The best band isn't the one you wish were open. It's the one most likely to do the job you want, in today's conditions, with the station you actually have.

Tell PropMap what you're trying to do and what you're working with. It uses the same live NOAA numbers as the rest of this page to suggest a first band, a fallback, and how confident to be.

First-move guidance

More views: solar panels, MUF map & absorption

Second opinions from two trusted sources. They refresh on their own; reload the page for the latest.

Solar-terrestrial summary (HamQSL)

Solar and MUF trend (HamQSL)

World MUF map (HamQSL)

D-region absorption (NOAA D-RAP)

Shows where HF is being soaked up right now, mostly on the sunlit side after flares. Red means HF is wiped out there. About D-RAP ↗

Panels courtesy of HamQSL.com (N0NBH) ↗ and NOAA SWPC.

How PropMap thinks

Beginner

PropMap tries to answer one practical question: which band should you check first for the contact you want, right now? It balances the sun's activity, time of day, the distance you're trying to cover, local noise and what your station can do.

Intermediate

No single number decides it. High solar flux makes the upper bands attractive, but they still lose if the path is too short (you'll skip right over the other station), the noise is high, or your antenna can't take advantage. Distance changes what "best band" means: a regional net and a DX contact want different things.

Advanced

PropMap is designed to improve your first move, not replace listening. The real test is always on the air.

Solar Cycle 25 context

Solar Cycle 25 began around December 2019 and is expected to remain elevated through the mid-2020s before gradually declining. Higher F10.7 flux generally means better daytime high-band (15m/12m/10m) propagation; elevated Kp/geomagnetic activity can degrade HF paths, especially polar routes, while boosting VHF aurora openings.

Want the full picture behind these numbers? NOAA's Space Weather Enthusiasts page ↗ and the ARRL propagation resources ↗ are both solid next steps for going deeper on any of this.