Ok, today I want to try and get some bits out of the signal I have, but perhaps I need to filter what I have first... Of course, I immediately got distracted by [minimodem](http://www.whence.com/minimodem/minimodem.1.html), which I want to use to verify the data, and either I'm not using it right, the recording is bad (it is very quiet...) or the data isn't ascii. Struggles on the sample in https://www.sigidwiki.com/wiki/CHU Someone posted a [Goertzel implementation in micropython](https://forum.micropython.org/viewtopic.php?f=3&t=7302&start=10), which seems cool and maybe useful. Goertzel seems like one way I could "decode" my signal by checking the amplitude of the two tones used in Bell 103. https://www.allaboutcircuits.com/technical-articles/fsk-explained-with-python/ claims to explain FSK, but there's way too much math in it for me and the code is for demonstration only I suspect. https://retrocomputing.stackexchange.com/questions/22169/why-kansas-city-standard-kcs-cuts-differs-from-bell-103-202-212-modem-protocol a good question and answer on why bell 103 is the way it is (has to work over a phone) https://github.com/cstroie/Arabell300 An arduino nano based modem that can do bell 103, could be really useful as a reference, but there's a lot of parts in C++ Also thought that ITU V.21 was the same as Bell 103, but apparently they use slightly different tones... https://mightydevices.com/index.php/2019/08/decoding-fsk-transmission-recorded-by-rtl-sdr-dongle/ this was really good, python / scipy walkthrough of decoding IQ data from an RTL-SDR, but assumes IQ data. Although... I think quadrature demod block in Gnu Radio uses the same thing? https://wiki.gnuradio.org/index.php/Quadrature_Demod I am a bit closer, but I'm still not sure how to take my signal and get some bits out of it...