I'm looking to better understand basic RF receiver circuits, and I thought building a basic AM 77.5 kHz receiver seemed like a good challenge. I do however have had quite a challenge in finding any resources on this. Do you know any good starting points for the basic circuits involved in building this, in discrete components if possible, as I would like to understand the details of the system?
If I understand correctly it should be possible without any kind of phase locked loop, and just with "simple" envelope detection as it is low frequency amplitude modulation?
Don't worry about the actual demodulation, I'm going to sample the signal and do it digitally. This is what I know how to do. 😉 So I'm only looking for the RF to baseband part.
Thanks in advance.
I was looking into it some time ago and it seems that the 77.5kHz band is very noisy (SMSPs and stuff) and it makes it quite difficult to build a good receiver for DCF77. Most projects are based on ready-made modules.
If you want to make something simple try building an analog AM receiver for local radio broadcasts. It should be easier (the signal will be stronger) and there are plenty resources on the net.
The Radio Spectrum Monitor may also be interesting to you albeit it is much more advanced project.