need help with DCF-77 time signal detection

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Hi,

Does anyone know a good method to receive the dcf-77 time signal, not using a complete chip but made up up with different components (like opamps, filters (LC), mixer (IC)...
We're working on a dcf-project at school and I was thinking to receive the signal with ferrit core antenne in parallel with a cap (matched on 77.5khz). I was told that I've got to bring down the frequency with a (balanced) mixer (otherwise the Q-factor of the filter must be extremely high). Can I use a second 77.5 khz signal (on the other mixerinput), so that there will be a DC-component and the double freq. Can I detect the information (= kind of AM pulses) out of this DC-signal (after LPF) or not?
The detected signal will be decoded by own written software...

Any comments or other ideas welcome!

Is it also possible to make a kind of low pass filter with an opamp based on the Gain Bandwidth Product (=constant). So the higher the Gain the lower the bandwith will be (so better selectivity).

Thanks in advance!!
HB.
 
BY THE WAY PROBLEM SOLVED

we just started to build and simply worked it out
 

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