A combined MSF/DCF atomic clock receiver

This is the atomic clock project that has it all - an Anthorn MSF receiver as well as a Mainflingen DCF receiver, all wrapped into a single neat little package.

For this to work you must obviously live in an area that can receive both signals. My circuit is based on two modules taken from two radio clocks bought at Lidl's supermarket. Originally both were for the DCF clock but by substituting the original 77.5kHz crystal with a 60kHz crystal, one of the modules was converted to MSF.

Notice that both antennas are lined up in my photograph. This is because Anthorn and Mainflingen - as seen from Limavady - are roughly in the same direction. The alignment of the ferrite rods obviously has to be adapted to your location.

Circuit description

The circuit is based on the single clock projects found elsewhere on this site. The supply for the two actual receiver modules makes use of a 3.3V zener diode. Supply voltage is 5V. The four links allow both the output signals and the LEDs to be inverted by moving the link. Each group of four NOT gates - on the pcb - consists of two 7400 NAND gates wired as Not gates.

The two signals are connected to digital inputs 5 (MSF) and 4 (DCF).

I found that the circuit worked extremely well and reception is near perfect under most conditions.

The pcb

A suggested pcb layout is on the left. A copy of the draw file for this circuit can be found in the zip file, the link to which is below.

The program

I have written a simple little single tasking graphics program which plots the output of both clocks one over the other. The MSF clock is yellow, the DCF clock is green. On the right is a small section of the output.

Not much can be learned. The most interesting bits are the beginning of minute markers. This is a half second ON for the MSF clock and a full second OFF for the DCF clock. Notice also the double pulse in first DCF second indicating a 100ms difference between atomic time and GMT. This used to be 400ms not all that long ago.

I have highlighted the interesting bits.

Here is a link to a zip file containing an executable file of the program, the BBC BASIC for Windows code below as well as the gif file for the pcb. I have also included a pdf file of the pcb art work.

msf_dcf_vel.zip version 2.2

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