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SDR communications receiver, and SDR police scanner using GnuRadio

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unclejed613

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https://github.com/unclejed613/gnuradio-projects-rtlsdr
these applications were built with gnuradio, using an RTL-SDR source block, but you can substitute any source block you want (such as hackrf or SDRPlay). the communications receiver also uses the 125Mhz offset for a Ham-it-Up HF upconverter, which can be changed for other upconverters. the communications receiver has AM/FM/USB/LSB modes. it has gain and squelch controls.
the scanner program uses a binary encoded frequency list and steps through the list. the scanner stops on squelch-break. there is a python utility for editing the list (there are two editors, one using a GUI interface, the other using a curses interface). the squelch-break can be a little finnicky.
the GUI interfaces for the radios are not well polished, and the apps don't have a lot of the features other programs (like GQRX) have. i wrote these for one of my sons, who is interested in amateur radio, and runs these apps on a raspberry pi, so the apps are somewhat lightweight. the scanner program was a bit of a challenge, because it seems nobody had tried to do this before. there were a few "scanners", but those programs would set the center frequency, and scan through the passband for signals, and save active frequencies in a text file. that's great for finding frequencies you want to look closer at later, but to step through a list of frequencies that were already known (and not be limited by the passband), nobody seems to have considered that kind of function would be useful, so there's no examples of reading from a file, and setting the radio to a stored frequency. some of the functionality of the scanner app needs some fine-tuning to improve squelch break interruption of the scanning. maybe a variable dwell time would improve it, but would slow down scanning, so it's a bit of a trade-off there.
 
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