
GNU Radio first steps: a FM receiver - marbu
http://www.abclinuxu.cz/blog/jenda/2019/11/gnu-radio-first-steps-a-fm-receiver
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segfaultbuserr
"You need a radio to play with GNU Radio" is the most common misconception.
There would be more fun if you have one, but GNU Radio itself doesn't require
a radio. It's actually a general-propose signal processing and simulation
tool, and a lot of things can be done without hardware.

For example, you can simulate different modulation techniques and observe them
in time and frequency domain, or you can simulate an amplifier and change its
the input level on an interactive GUI control panel you programmed to
understand how an overdriven/saturated amplifier produces intermodulation
distortion, or experimenting with different transmitter/receiver architecture
(superheterodyne, direct conversion, etc).

Traditionally, these experiments can only be done in a lab with a scope and a
spectrum analyzer. But now it's all possible on your desktop.

~~~
apcragg
That is a good point that you don't need a radio but I work extensively with
GNU Radio and I would do all of those experiments using MATLAB / Octave. GNU
Radio is very much the wrong tool for that job.

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CraigJPerry
I made an SSB receiver in GRC, that was educational. SSB doesn’t have a
carrier so you have to provide your own (GRC has a block that can generate a
sine wave of a given frequency). The ability to probe the graph anywhere makes
learning easier in a way that physical building wouldn’t be.

Ironically i was doing a bit more on my little RTL SDR web view tonight:
[https://github.com/craigjperry2/websdr](https://github.com/craigjperry2/websdr)

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crusso
Anyone have good suggestions for playing around with SDR on OSX? I tried
installing GNU Radio a couple of years ago with homebrew and it was quite a
mess.

~~~
n8henrie
I got one last week and have had good luck with
[CubicSDR]([https://cubicsdr.com/](https://cubicsdr.com/)) which is brew
installable, as well as decoding APRS packets from the command line using
rtl_fm and multimon-ng

I'm hoping to figure out how to decode satellite pictures in the near future.

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madengr
I’ll plug the scanner I wrote. It’s not a normal scanner, in that it allows
parallel demodulation and recording of FM and air-band AM:

[https://github.com/madengr/ham2mon](https://github.com/madengr/ham2mon)

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lucb1e
An FM receiver is the first thing in every GRC tutorial. I just wish there was
something useful that one can receive with one of these standard $15 RTL-SDR
receivers that isn't super complicated or FM radio.

~~~
blihp
There are all sorts of interesting and useful things you can do with them:
monitor/troubleshoot various AM devices around the house (weather stations,
garage door openers etc), tune in to a number of amateur radio bands (there's
surprising amount of traffic on them), receive NOAA weather broadcasts,
aircraft broadcasts, debug DIY projects (433MHz transmitters etc.)... there's
a _lot_ of stuff being broadcast in the frequencies that these dongles can
receive. You just need a decent antenna[1] and to explore the spectrum around
you a bit.

Granted, the absolute most common cases are out of reach with the cheap
dongles due to frequency, bandwidth and encryption issues (i.e. ATSC, Wifi,
Bluetooth) So they're not going to be terribly interesting to the average
consumer but they are very handy little devices for hackers with any interest
in RF.

[1] The default antennas they ship are _not_ useful over a wide range of
frequencies and/or for weak signals

~~~
dTal
The 433Mhz band is quite interesting - key fobs, garage door openers, and
other cheap and cheerful "wireless" technologies often work on this band. Part
of the fun is finding out what! Tune your SDR and go hunting...

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nullc
The rise of internet radio has made it pretty difficult to obtain a really
good FM tuner these days regardless of the price.

In fact, I'm not aware of anything with real diversity reception-- at most
they're limited to crossfading two tuners, and even that is mostly a car radio
feature.

I wonder if anyone has been working on an open source state of the art SDR
broadcast FM receiver.

A good receiver would have denoising of the stereo signal, filters to
eliminate HD radio interference, PLL/matched demod of the stereo signal, and
support diversity reception using constant modulus algorithm or similar.

~~~
xxpor
It's a damn shame the Icom IC-9700 doesn't support out of band RX

~~~
nullc
Or WFM :)

IC-9700 is an impressive looking radio.

I think amateur VHF/UHF/SHF SDR are really a long way from what state of the
art should be in those bands, but are most just porting HF SDR to a new set of
bands.

VHF+ SDR should be all about beam forming, broad band modes (spread spectrum),
digital, etc. There is so much more spectrum available (esp in 23cm), and its
so much easier to put up multiple antennas.

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epx
Just in case:
[https://epxx.co/artigos/pythonfm_en.html](https://epxx.co/artigos/pythonfm_en.html)

~~~
MrRadar
Is that your site? If so, please consider changing the "B612"/"B612 Mono" font
to something else. The parenthesis in it look far too much like square
brackets (at least as rendered by Firefox on Windows 10 with subpixel AA
enabled on a standard DPI LCD monitor). In particular the default font makes
the quoted Python code in the linked AM Modulation article almost unreadable
(it took me a solid minute to realize you were _calling_ math.sin/math.cos
instead of trying to index them for some reason).

~~~
epx
I really like the B612 font, while I agree the bracket^Wparentheses are
strange. Any font suggestions?

~~~
MrRadar
I don't have a particular suggestion. I used the Developer Tools to disable
the CSS font directives, so maybe just have an option to switch to a
stylesheet that doesn't specify specific fonts?

Also, thanks for your articles. I find them very well-written. I'm reading
through the one on impedance right now and it's a very clear explanation of a
concept that that can be somewhat confusing.

~~~
chrisseaton
> maybe just have an option to switch to a stylesheet that doesn't specify
> specific fonts

Can’t your user agent do that?

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hatsunearu
holy FUCK

GNU Radio has such horrible documentation I can never get right. I tried
decoding APRS with GNU Radio but I gave up because there's like approximately
0 documentation on what the GFSK decode block does.

I can't believe I advocated for this project. Learning GNU Radio generally
requires talking to a guru to pass the information via oral history.

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cellular
My phone has radio but no television reception. Is there some legality reason
why phones don't have tv tuners?

~~~
simcop2387
Maybe actually. In some jurisdictions this would require a license from the
government to do the reception. The UK is like this with their tv licenses for
the BBC and similar. I can't imagine theyre the only ones like this. And then
there's possibly compression technologies that might need to be licensed from
the mpeg group, etc.

~~~
xxpor
You'd also want a much better antenna than what you could fit in a phone.

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classified
Very welcome. I've been wanting to play with GNU Radio for a while but I
didn't quite know where to start.

~~~
rhinoceraptor
Michael Ossmann's video series is another great resource:

[https://www.greatscottgadgets.com/sdr/](https://www.greatscottgadgets.com/sdr/)

