radio clock

3 Articles

So Long, CHU, And Thanks For All The Time Signals

May 27, 2026 by 59 Comments

In the long ago, pre-internet days when your clock project wasn’t an ESP32 getting its timing via NTP over WiFi, it was still possible to build a wirelessly-updating clock. All you needed was a shortwave receiver tuned to a time signal — perhaps like the National Research Council of Canada’s CHU, found on the dial at 3330, 7850, and 14 670 kHz. At least, it can be found at those frequencies until June 22nd, 2026, when the station will finally go dark.

Depending where you were on Earth, it might have been easier to tune into CHU than the United States based WWVB, or one of the various European signals like DCF77 or the UK’s MSF. If you’re not into radio, all these time signals have essentially the same job, if you hadn’t guessed: tell the time. This can be done in a variety of ways, and CHU has made use of more than one of them since its establishment in 1923.

Initially, the time was sent in Morse code, but later they added a speaking clock for easier human listening in both Canadian French and English. For synchronizing radio clocks, a series of pulses is given in DUT1 format using 0.3s pulses — which is what older clocks would have been listening to — and nowadays a digital FSK time code for more modern equipment. You can have a listen through the video by [Shortwave Listener] embedded below.

It’s not our place to judge the Government of Canada for trying to save money where they can. It wasn’t so long ago that WWVB was in danger of shutting down for similar reasons. But we’re still going to miss those beeps. If you do tune in before the station goes dark, CHU should still be giving out QSL cards. Get yours before it’s gone forever.

If you do have a clock that relies on this time signal, don’t worry. You can make your own, perhaps with a GPS time source.

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Atomic Clock Trades Receiver For An ESP8266

April 7, 2025 by 20 Comments

The advantage of a radio-controlled clock that receives the time signal from WWVB is that you never have to set it again. Whether it’s a little digital job on your desk, or some big analog wall clock that’s hard to access, they’ll all adjust themselves as necessary to keep perfect time. But what if the receiver conks out on you?

Well, you’d still have a clock. But you’d have to set it manually like some kind of Neanderthal. That wasn’t acceptable to [jim11662418], so after he yanked the misbehaving WWVB receiver from his clock, he decided to replace it with an ESP8266 that could connect to the Internet and get the current time via Network Time Protocol (NTP).

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Well Engineered Radio Clock Aces Form And Function

March 22, 2017 by 22 Comments

Clocks that read time via received radio signals have several advantages over their Internet-connected, NTP-synchronised brethren. The radio signal is ubiquitous and available over a fairly large footprint extending to thousands of kilometres from the transmitting antennae. This allows such clocks to work reliably in areas where there is no Internet service. And compared to GPS clocks, their front-end electronics and antenna requirements are much simpler. [Erik de Ruiter]’s DCF77 Analyzer/Clock is synchronised to the German DCF77 radio signal, which is derived from the atomic clocks at PTB headquarters. It features a ton of bells and whistles, while still being simple to build. It’s a slick piece of German hacker engineering that leaves us amazed.

Among the clock functions, it shows time, day of the week, date, CET/CEST modes, leap year indications and week numbers. The last is not part of the DCF77 protocol but is calculated via software. The DCF77 analyzer part has all of the useful information gleaned from the radio signals. There are displays for time period, pulse width, a bit counter, bit value indicator (0/1) and an error counter. There are two rings of 59 LEDs each that provide additional information about the DCF77 signal. A PIR sensor on the front panel helps put the clock in power save mode. Finally, there is a whole bunch of indicator LEDs and a bank of switches to control the various functions. On the rear panel, there are RJ45 sockets for the DCF77 receiver antenna board, temperature sensor and FTDI serial, a bunch of audio sound board controls, reset switches and a mode control switch.

His build starts with the design and layout of the enclosure. The front panel layout had to go through a couple of iterations before he was satisfied with the result. The final version was made from aluminium-coated sandwich-panel. He used an online service to photo-etch the markings, and then a milling machine to carve out the various windows and mounting holes. The rear panel is a tinted acrylic with laser engraving, which makes the neatly laid out innards visible for viewers to appreciate. The wooden frame is made from 40-year-old Mahogany, sourced from an old family heirloom desk. All of this hard work results in a really professional looking product.

The electronics are mostly off the shelf modules, except for the custom built LED driver boards. The heart of the device is an Arduino Mega because of the large number of outputs it provides. There are seven LED driver boards based around the Maxim 7221 (PDF) serial interface LED drivers – two to drive the inner and outer ring LEDs, and the others for the various seven-segment displays. The numerous annunciator LEDs are driven directly from the Arduino Mega. His build really comes together by incorporating a noise resilient DCF77 decoder library by [Udo Klein] which is running on a separate Arduino Uno. All of his design source files are posted on his GitHub repository and he hopes to publish an Instructable soon for those who would like to build one of their own.

In the first video below, he walks through the various functions of the clock, and in the second one, gives us a peek in to its inside. Watch, and be amazed.

Thanks for the tip, [Nick]

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