It is no secret that all operating systems are able to synchronize system time with a reference atomic clock using the NTP protocol.
In a similar way, some wristwatches, stationary clocks, and weather stations can receive a radio signal carrying precise time data and synchronize their displayed time with it.
I ran into a synchronization problem with a Casio PAW1300 using the DCF77 antenna while in Dnipropetrovsk, right on the edge of the reception area, about 2000 km away.
According to the manual, for successful synchronization in a weak reception zone, the watch should be placed overnight on the windowsill of a west-facing window. Signal quality is also affected by weather, time of year, “noisy” devices, and nearby buildings.
Unfortunately, without any additional tools, I could not synchronize the watch in summer, in clear weather, in early to mid-August.
There were several possible solutions:
- Citizen Wave Receiver (RCW/SU-3 for DCF77) — a signal amplifier from Citizen. A simple and fragile device priced around 20-30 euros.
- DCF77 Time Receive Module — calling it a device is generous; in practice it is a ferrite rod with a coil, a capacitor, and a small controller that decodes the received data. Price on eBay: about $15 plus shipping.
- Tape measure / kettle / radiator / thermos / fan — all of these can act as an antenna. If you strap the watch to one of these overnight, you can slightly amplify the signal and improve the chances of synchronization.
- A homemade amplifier antenna — the best option in my opinion. This is the method I chose, and in the end the watch synchronized successfully. Below I explain how to build a simple amplifier antenna yourself.
Making an amplifier antenna for DCF-77
You will need:
- Any low-voltage capacitor. Ideally 2400 pF, though I used 2200 pF.
- Enameled single-core wire, 0.2 mm or thicker.
- A cardboard box measuring 110x50x20 mm.
- Tape.
- A soldering iron.
So, let’s begin:
- Mark out a 60 mm section on the box.
- Wind the wire around that section. You need 300 turns total: 4 passes of 75 turns each.
- Solder the capacitor to the ends of the wire.
- Wrap the whole thing in tape for protection.
It should look something like this:
At night, put the watch onto this “device,” point the 12 o’clock mark west, and place it near the window. Now, with a very high probability, if you are in Ukraine or the European part of Russia, your watch will be able to synchronize with DCF-77.
Who needs that kind of precision?
There are professions for which precise time is critically important, for example a subway train driver. For such people, being late even by one second can mean a penalty.
Fortunately, I am not a subway train driver, but if a watch has a time synchronization function, I think it would be unreasonable not to use it. Especially since for an accuracy of plus or minus one second per month, it is enough to leave the watch overnight on a west-facing windowsill once a week.