A pocket-sized ham radio clock that shows who is hearing you, right now.
UTC · propagation · nearest ionosonde · live PSKReporter spots on a list and a world map, on the tiny OLED of a Heltec WiFi LoRa 32 V3.
Call CQ on FT8, glance at your desk, and see the stations that decoded you pop up on the display, with band, SNR and distance, and as dots on a map with the day/night terminator. Between QSOs it is a clean UTC clock with solar data and a band recommendation for NVIS. No app, no account, no cloud of your own: the board talks straight to public ham radio data feeds over Wi-Fi.
- 🕐 Clock: big UTC with seconds, date, and local time with automatic daylight saving time (about 50 city regions plus fixed UTC offsets).
- ☀️ Propagation: solar flux, sunspot number, A and K index, X-ray class and HF band conditions for day and night (N0NBH).
- 📡 Nearest ionosonde: foF2 and MUF(3000) from the closest GIRO ionosonde with a fresh measurement, picked automatically from your locator, plus the recommended NVIS band.
- 👂 Who hears me: live PSKReporter spots of your callsign over MQTT, any mode that gets
decoded automatically (FT8, FT4, JS8, PSK, RTTY, CW…). Your
/Pand/Mvariants are included. - 🗺️ Map: world and Europe views with the day/night terminator, plus optional Czechia, Germany, UK and USA maps. AUTO zooms to fit your spots, and new spots pulse.
- 🌙 Kind to the OLED: screen saver (off, Game of Life, or dim and shift), night mode, and an optional wake-up when a new spot arrives, with an LED flash if you like.
- 📱 Easy setup: install and set up in one browser page over USB, or from your phone through the board's own Wi-Fi hotspot. No passwords in the firmware, and entering setup never erases what you saved.
- 🌍 Localized: English, Czech and German on the display and the setup page, and easy to translate.
- 🪶 Lightweight: plain C++ on the Arduino core, with no external libraries.
 Clock UTC, date, local time, callsign and locator |
 Propagation SFI, SN, A, K, NVIS band, X-ray, foF2, MUF, band conditions |
 Heard me: list callsign, band, SNR, km; sorted by time or distance |
 Heard me: map home square, spots, dotted land in daylight |
Screens rendered from the firmware's own font and map data, with example values.
- A Heltec WiFi LoRa 32 V3 (ESP32-S3 with a 0.96″ 128×64 OLED). The LoRa radio is not used.
- A USB-C cable and a 2.4 GHz Wi-Fi network.
- A USB charger or power supply. microHAMCLOCK is meant mainly for stationary use on your desk, plugged in all the time; a battery is not needed.
- Your callsign and Maidenhead locator.
- Optional, recommended: a 3D-printed case. The Bender Battery Case for the Heltec V3 by zerofox3D on Printables fits well: it clips together without screws, keeps both buttons (PRG and RST) reachable, has a bay for an 18650 battery and an optional on/off switch. The model is free for personal use only, so please don't sell prints of it.
-
Flash it in one click: open the web installer in Chrome, Edge or Opera on a computer, plug in the board, press Install. That's it, no tools to install.
Prefer to flash by hand?
Download
heltec_v3_microhamclock-merged.bin(always the latest release; older ones are on the releases page) and write it at address0x0, for example with esptool-js or from the command line:esptool.py --chip esp32s3 write_flash 0x0 heltec_v3_microhamclock-merged.binIf the board does not connect, hold PRG, tap RST and release PRG.
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Set it up right on the same page: press Connect to microHAMCLOCK, pick your Wi-Fi from the list, enter the password, your callsign and locator, and Save. The page then shows the board connecting to Wi-Fi, getting the time and listening for your spots.
No computer at hand? The board also starts a Wi-Fi hotspot called MICROHAMCLOCK-xxxx. Join it with your phone and the setup page opens by itself (or go to
http://4.3.2.1). -
Get on the air: call CQ in FT8 and watch the list fill up as stations hear you. (WSJT-X reports to PSKReporter about every 5 minutes.)
Need to change something later? Hold PRG for 10 seconds to get back to the setup page.
One button, PRG:
| Press | Action |
|---|---|
| Short | next screen |
| Double | automatic screen switching on/off (15 s per screen by default) |
| Triple | status screen (Wi-Fi, IP, MQTT, data age, battery voltage, version) |
| Long (0.7 s) | list: sort by time or distance · map: AUTO → WORLD → EUROPE (→ CZECHIA → GERMANY → UK → USA, when switched on) · status screen: power off (RST starts the board again) |
| Hold 10 s | setup mode (hotspot) |
microHAMCLOCK only shows data that others kindly make public. Thank you to:
- PSKReporter by Philip Gladstone, N1DQ, and its live MQTT feed by Tom Fanning, M0LTE: the reception reports.
- N0NBH, Paul Herrman: solar and band condition data.
- KC2G, Andrew Rodland, KC2G, who republishes the ionosonde measurements, and the GIRO ionosonde network (Lowell GIRO Data Center, University of Massachusetts Lowell) with the observatories that run the stations: foF2 and MUF measurements. The station in use is shown on the status screen, and the observatory contacts are in the GIRO Acknowledgements List. GIRO data is released under CC BY-NC-SA 4.0. Source: Reinisch, B. W., and I. A. Galkin, Global Ionospheric Radio Observatory (GIRO), Earth, Planets and Space, 63, 377–381 (2011), doi:10.5047/eps.2011.03.001, http://spase.info/SMWG/Observatory/GIRO.
- Natural Earth: public domain map data.
- NTP: ntp.ufe.cz (the Czech national time standard),
tik.cesnet.czandpool.ntp.org.
The project uses PlatformIO:
pio run # build
pio run -t upload --upload-port COM4 # flash
pio device monitor # serial console, 115200 baud
The source layout, the console commands for testing, the map generator and the other tools are described in docs/development.md.
Display and web texts live in src/lang/<code>.inc, so a new language is mostly one file to
translate. Pull requests with new languages are very welcome; the steps are in
CONTRIBUTING.md.
- Manual: installing, setup, screens, controls, screen saver and night mode, advanced settings, troubleshooting, data sources.
- Development: building from source, how it fits together, tools.
- Changelog
microHAMCLOCK is a tribute to HamClock by Elwood Downey, WB0OEW (SK), the clock that has graced so many shacks, which the community keeps going as OpenHamClock. microHAMCLOCK is a separate, much smaller project with its own code. It is not affiliated with HamClock, the Clear Sky Institute or microHAM s.r.o.
microHAMCLOCK was designed and tested by OK2MTB and written with the help of AI: the code and documentation were developed in conversation with Claude (Anthropic) in Claude Code. Every feature was decided by a human and verified on real hardware.
Bug reports and pull requests are welcome. Before a pull request is merged, contributors agree once to the Contributor License Agreement: you keep the copyright, and the author may also publish the project under other terms besides the GPL. Details are in CONTRIBUTING.md.
Copyright (c) 2026 Matěj "Wolf" Holyszewski, OK2MTB.
microHAMCLOCK is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
The firmware binaries also contain the Arduino-ESP32 core (LGPL-2.1) and ESP-IDF components (mostly Apache-2.0), under their own licenses. The map data is public domain (Natural Earth).
73 de OK2MTB