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As the new Java.net infrastructure contains project-level wikis, this main wiki will be shut down in the near future. For wiki page export and general wiki questions please contact the site admin at communitymanager@java.net. DIY Radio Clock
DIY radio clock receivers can be built for under 30UKP, 20USD, 30Euro. It is also possible to read the time and date from non-authorative clock sources that provide better than 1 second accuracy, such as the FIG0/10 packet from DAB radio transmissions with little effort.
My first DIY radio clock
My first DIY radio clock was built using the Galleon EM2S MSF development board and a home-made antenna, plus the interface circuit from Jonathan Buzzards webpages (URL below). The interface circuit worked well but I modified Jonathans sourcecode to improve interference handling (caused by the close proximity of a number of computer systems and associated monitor screens). I intend to make further modifications to oversample the data stream when in the "-p" mode. I haven't sent my changes to Jonathan yet and they aren't available on the web - please email me directly if you would like a copy.
Deviations from Jonathans instructions
I chose to use a 1/4W resistor rated at 60 degrees working temperature and good heat dissipation. Rather than solder the resistor across the LP terminals, I traced the wires back and soldered between the collector of the small surface mount transistor V1 and the LP4 end of the surface mount resistor near LP4. I trimmed and covered the legs with heat-shrink before soldering in place. I mounted the transistor by passing the base and collector legs through the holes in the LP pads then soldered and trimmed the legs, bending the emitter leg away from the board so that the blue lead may be soldered to it. Finally, I soldered the legs of the electrolytic capacitor to the board and soldered the red and earth leads to the capacitor end of its legs.
Antenna design
If you live in the UK, are using the EM2S board and are at least reasonably competent with electronics, you can achieve good results by combining the
The MSF signal is strong even inside metal framed buildings throughout much of the UK. The EM2S circuit is good at discrimintaing the signal presented to it, so the antenna does not have to be too precise.
To get the antenna to resonate at 60KHz (the frequency on which Rugby MSF station transmits), it has to be matched with the appropriate value capacitor. I won't go through all the theory, the references below are a ggod starting point, but surfice to say that a 3.2mH (millihenry) coil in parallel with a 2200pF capacitor will resonate at 60KHz.
On a 44mm diameter air form, such as a toilet roll, between 359 and 366 turns will be needed depending on the thickness of the wire. As the number of turns is so great, the resistance is fairly high (it also takes rather a long time to construct), it is preferable to either use a ferrite form or tune to one of the harmonics of the signal. Radio engineers tend to talk about wavelengths rather than the harmonics themselves - 1/2, 1/4 and 5/8 wavelenghts are popular among radio engineers.
For a 10mm diameter ferrite rod 60-80mm long, you will need between 98 and 114 turns for optimum reception. For a 10mm diameter ferrite rod 40mm long, around 80 turns will be needed.
1/4 wavelength requires a 200mH coil, which could be achieved on a 44mm diameter air form with between 80 and 100 turns (closer to 80 turns with fine guage wire).
In each case, the 2200pF capacitor should be soldered across the ends of the coil as close to the coil as possible. For other combinations, the calculators at the last two URLs in the references section should help you determine the characteristics to use.
Futures
I plan to create a receiver based on the MK484, UE6002, CME6005 or UE6005 receiver IC and the Galleon tuned antenna, which should cost around £15 to build. It is likely to perform well only in strong signal areas - which will be fine for me. Other ICs to check out: U4221, U4224.
References
-- MichaelDavey - 15 May 2004
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