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Ham radio — runs in your browser, nothing to install

FT8Web — a complete FT8 client running entirely in the browser, with WebSerial CAT control → ft8web.ok1cdj.com

WSPR Lab — compare the real-world performance of two antennas using global WSPR data: gain, coverage, propagation efficiency → wsprlab.ok1cdj.com

DX Radar — live DXpedition dashboard combining DX Cluster and RBN spots with your Club Log data, so you see at a glance what you still need → dxradar.ok1cdj.com

Calculators — coil-loaded shortened dipoles and verticals: loading inductance, radiation efficiency, matching network and SWR bandwidth → calc.ok1cdj.com

Trainer — phonetic alphabet drill → trainer.ok1cdj.com

VHF Sim — VHF contest simulator → vhfsim.ok1cdj.com

All of them in one place: apps.ok1cdj.com

Mudita Kompakt — apps that keep the phone quiet

The Kompakt is the best digital detox device I've used, and I write apps that respect that. Native Kotlin/Compose, built for the 800×480 E Ink panel. No Google Services, no background services, no notifications, no tracking.

kRadar — precipitation radar. RainViewer imagery over a vector map, centred on your GPS position, with two hours of animated history. Frames are quantised to grey levels so the radar is actually readable on E Ink, and playback runs from memory with no network. Worldwide coverage.

kCompass — GPS, compass and QTH locator on one screen. Position in decimal degrees, DMS and 8-character Maidenhead (tap to copy), magnetic or true north, and GNSS satellite status with per-satellite signal strength. A Freeze button stops every live update so the panel holds a readable value instead of flickering. Built for POTA/SOTA and antenna work.

kVexed — Vexed, the classic sliding-block puzzle. 48 packs, 2800 levels, par counts, unlimited undo. No network and no permissions at all.

kSread - A minimal speed-reading (RSVP) app. Words are flashed one at a time with the focus letter aligned to the eye's Optimal Recognition Point, so you read without moving your gaze.

kChat - OpenAI-compatible LLM chat client for the Mudita Kompakt e-ink phone

APKs and install instructions: kapps.ok1cdj.com

Why this needs coffee

A VPS, a handful of domains and test hardware. That's the whole budget, and it's mine. Two coffees keep FT8Web, WSPR Lab and DX Radar online for a month. Everything stays free and open-source either way — support just keeps the lights on and buys me the evenings to keep building.