![]() ![]() With my test clock it takes around 3.5 minutes. You have to wait a few minutes until your clock accept your time signal after you triggered the sync. If you want to reproduce it: Please make sure your system supports 192 kHz (on Windows you can find the setting in the Control Panel) and your radio controlled clock is next to your speaker. I tried to make a proof of concept for this, but the WebAudio API of Chrome seems to be buggy at the moment and Firefox only provides me with a sample rate of 44.1 kHz.īut I guess that are just some small problems (please tell me, when you implemented that for a browser :-) ). Webbrowser provide several methods to play sound, so the visitor of a website could unconsciously become a jamming transmitter. This means you could use this as an attack. You cannot hear (nearly) the transmission. The cool thing with the hack is that you can use nearly every player with 192 kHz as transmitter. The signal would get overdriven and a higher bandwidth by software, so that the result would be worse. The volume in VLC shouldn't be over 100%. To get the best possible result you have to set your system volume to 100%. You can trigger the sync by removing the batteries for a few seconds (some clocks also have a sync button). Ususally a radio controlled clock only syncs every few hours. You can play the file with any media player (e.g. I wrote a small C program which generates several minutes of the signal and saves it as WAV file. The encoding of the signal is very easy and is publicly documented. The receiver module of the clock interprets the generated carrier of the sound card as original DCF77 signal and tries to decode it. However, the amplifier and magnet of the speaker get a high-frequency current and act like an antenna. Humans cannot hear this frequency (and speakers shouldn't generate big acoustical waves here). A sound card with 192 kHz is able to generate a frequency with up to 96 kHz. TechnicalĭCF77 sends the signal with a relative low frequency of 77.5kHz. Of course it doesn't have to be a notebook, it can be a normal workstation too. ![]() The operating system is not really important. There are no special requirements for the computer, except it must have a sound card with a sample rate of 192000 Hz (but this is common today). I guess a bigger sound system with amplifier can reach up to several meters. The speaker of my personal notebook can control clocks in a range of approximately 60cm. The internal speaker (or any speaker) can influence the receiver module of the clock. All you need is a notebook (alternative: a flux capacitor -) ) to set radio controlled clocks nearby to any desired time. The signal will be "sent" through the speaker output. Now I want to show you how a computer can also send and not just receive this signal. The transmitter is located near Frankfurt in Germany and sends the current time to radio controlled clocks within a radius of several 1000km. ![]() This article and program is only made for research.Ī few month ago I presented my project, where I received the radio signal of the time signal radio station DCF77 with just a notebook and an old piece of a headphone cable. I discourage from misuse the described effect. This might be illegal, so it is advisable not to do that besides you really know what you're doing. This covers most of Central and Western Europe, including the UK, France, Netherlands, Belgium, Denmark, Switzerland, Northern Italy.Caution: By playing these audio files, you may cause electromagnetic disturbances. The time code signal can be received upto 1500km from Frankfurt. The DCF radio time code signal is broadcast from Frankfurt, Germany, the coverage of the DCF signal is the whole of the Germany. Identifying the best DCF signal coverage What is the coverage of the DCF time signal ? Galleon Systems Unit 9 Fortnum Close Kitts Green Birmingham B33 0LG UK +44 (0)1 ![]()
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