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The frequency domain section is definitely worth reading: https://pysdr.org/content/frequency_domain.html
It explains so many concepts that one might get confused about when diving into SDR or radio and signals in general.
Yes, having worked a few things on frequency domain without having a formal education on those concepts, when I read that part I thought to myself "wish I've had this intro 5 years earlier".
If anyone is looking for practical entry level SDR projects, then rtl_433[1] is a great project to receive 433Mhz alarm from cheap fire/gas alarms using a DVB-T dongle and raspberry pi.
Previous discussion:
https://news.ycombinator.com/item?id=24750588
Really clear and practical writing style by the way.
This is an excellent resource, "learn how to design a radio communications channel" more than "listen to the police on your $20 usb stick".
Things like RTL-SDR sticks are much fun (I've got 2 running at the moment); things like LimeSDR are immensely exciting... and there's been a lot of progress in the 12?+ years SDR has been developing as a hobby. But.
It still feels unformed and natal. Like "personal computing" before the post IBM PC boom. Lots of "this will be big" but not a lot of practical uses for a wider market yet.
Maybe the MIMO/passive radar tricks will turn out to be the solution to digital 3d spatial sensing or something and we'll get direct sampling of GHz at a time to play with.
Ooh, neat! ~5 years back I got really excited about SDR to receive AIS [1] transmissions. But after a couple of weeks of frustrating attempts, I threw everything in the garbage and just bought a commercial AIS receiver. Are things better now? Do HNers have recommended hardware/software starting points?
[1] https://en.wikipedia.org/wiki/Automatic_identification_syste...
This popped up recently on rtl-sdr.com - https://www.rtl-sdr.com/building-a-raspberry-pi-based-ais-re...
Having a good antenna/filter/LNA is important and will likely put you in equivalent or better performance range than any personal-use grade commercial offering.
Do you recall what the major problem was at the time?
I definitely remember the software seeming terrible. Flaky, quirky, hard to wrangle. So much so that I couldn't tell if there were really also hardware problems. Since my goal was to have something that ran reliably for years without attention, and since proper AIS receivers at the time were only a couple hundred bucks, it quickly seemed that professional gear was a better ROI.
And thanks for the link, I'll check that out. At first pass it requires me emailing somebody to get a link to their software image, which seems odd, but I may take a swing at it. Do you have a guess as to what software they're using?
I've run this setup with an ADSB antenna on a cheapo rtlsdr while sitting on a pier and was amazed at how far out i was picking up ships from.
Made a program that interfaced w/ my SDR to make it take FM radio as input. Unfortunately I only did so via using a virtual audio output stream; ie, I had to fiddle w the channel in SDR#. Next step would have been to include FM decoding, so I could change the channel from within the program!