Who made this

Skywave is a free daily puzzle about HF propagation. I'm Arthur, and I built it on my own in Lincolnshire.

This is a game, and the propagation is simplified on purpose, so please don't plan a real contact with it. For real conditions use VOACAP or a live propagation map.

Why I built it

I'm studying for my Foundation licence, and HF is the next rabbit hole. Skywave is how I'm learning propagation.

Me and radio

I'm into planes and I live near RAF Coningsby. I got into SDR recently: instead of using Flightradar all the time, I bought a Raspberry Pi and an SDR to pick up ADS-B myself. There's now a retro radar-style screen running 24/7 at home, showing flight info and a few other bits.

Arthur sitting in the cockpit of a light aircraft — Me in the right seat. Planes came first, radio followed.

Things I know are simplified on purpose

If you know HF properly, some of this will make you wince. It's a game, so I've kept the model small enough to play in a browser:

Only the short great-circle path is modelled. There's no long path.
The F2 layer sits at a fixed 300 km, and every layer is drawn 8 times higher than scale so you can see the hops.
There's no single LUF figure. The game checks whether absorption and noise leave enough signal to decode.
The A index is worked out from K, so it isn't a separate penalty.
The night-side city lights are an illustrative texture made for the game, not NASA imagery.
Every station is made up (more on that below).
The FT8 warble and the SSB noise are sound effects, not real transmissions.

The guide has the details, including the numbers behind the scoring.

The stations are made up

Callsigns are built from real ITU prefix families with random suffixes. Every station is fictional, and any match with a real one is a coincidence. The model is a simplified game, not a forecast, a real DX cluster or a transmitter.

What's stored, and where

Everything stays in your browser. The daily conditions and stations are worked out from the UTC date, and your progress, settings, best scores and streak are kept in this browser's localStorage. Practice rounds don't touch your daily streak. There's no backend, no accounts, no audio recording, no cookies and no advertising. I count visits with Cloudflare Web Analytics, which sets no cookies, only gives me totals and never sees your game. See cookies and storage for how to clear it all.

The only things loaded from elsewhere are the pinned three.js library and its addons (from jsDelivr) and Cloudflare's small analytics script. The Earth images and the game code come from this site. The gear and coffee links only leave the site if you click them.

Credits and data sources

Day map: NASA Blue Marble, from the Basemap data package, resized and compressed. Used under NASA's media guidelines. NASA doesn't endorse this game.
Night map: the city lights are an illustrative texture made for this game, not NASA imagery. For the real thing, see NASA Black Marble.
three.js r185 (0.185.0) and its addons, under the MIT licence.
Land mask: made from public-domain Natural Earth data.
Callsign prefixes: the ITU call-sign series.
Sound: made in your browser with WebAudio. There are no audio files or web fonts.

Full credits and source URLs are in CREDITS.md.

Things for the shack

A few things from my 3D print shop, and a desk mat, if they're any use to you.

An EFHW toroid box, a 3D-printable box for FT240 and FT140 cores (49:1 or 9:1 unun, or a choke): on Cults3D
RF connector panel drill guides for SO-239, N (4-hole flange) and BNC (D-hole): on Cults3D
A desk mat with the UK amateur band plan from 160m to 70cm: see the desk mat

If you'd like to buy me a coffee

Skywave's free and staying free. If you've enjoyed it, a coffee helps.

Under the hood

Plain JavaScript, HTML and CSS, with no build step. The propagation model is kept apart from the renderer, so its tests run without three.js. If WebGL2 or the CDN isn't available, a labelled 2D map keeps the radio desk playable.

You can see what I've changed and when in the log.

Tell me what I got wrong

Spotted something a real operator would wince at? Email me: hello@dexmlabs.app. 73, Arthur

Skywave is part of Deus Ex Machina Labs. Here's the privacy notice, cookies and storage, the terms and the disclaimer, or you can get in touch.