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very low frequency tech postings  -   04 2003
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Fri, 25 Apr 2003

das clock fake 77

'das clock fake 77' is a radio transmitter.

dcf77 screenshot


This program paints black and white stripes on your screen. Your monitor will now emit electromagnetic waves. Basically a carrier frequency of 77500 Hz. In Europe commonly used DCF77-radio-clocks will tune into that frequency and listen ... to be honest, only if they're close enough to your monitor they may/might. The screen image will be modulated to emit the 59 information bits plus the one sync bit per minute. Actually we only need to switch between two static images once per second, but with a high timing precision of about 50ms. Nothing evil will happen to your monitor or LCD, we're not playing with your modelines or the sync of your monitor. The program uses the SDL-library to acess the screen, this can be a problem when you don't have HW-acceleration - I had to switch back to 16bpp on my X to get the required 20fps. The program now tests wether the screen performance is sufficient to achieve the required 20 fps.

See the README for more details. Get it here.


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