Re: contemplating conversion of an r-pi3b based system to a rock64
> Somebodies quoteing is broken, I didn't write that. I believe Alan Corey
> did.
Yes, I'm in Gmail, I quote manually by copying and pasting
>> I've not really bothered with HAM stuff since I was playing with
>> Packet Radio before dial-up Internet became a thing, but I find your
>> claim that there's nothing much for Unix, suspicious:
I meant nothing in the sense of GUI SDR programs where you can see
signals and click on them. It's neat because you can tell an AM
signal from an FM or SSB by looking at it, and most ham bands are
small so you can see the whole thing at once and pick a quiet
frequency that way. A waterfall shows history so you can tell what's
been quiet for 5 minutes or so. People were doing Packet with TNCs
(Terminal Node Controller) a long time before PCs were fast enough to
sample and decode audio even. My first exposure to it was feeding
audio from my Icom radio into my soundcard and it could act as a
modem, I didn't have to buy anything extra. But that's not SDR.
>> Long ago (early-mid 90s) part of what caused people to be interested
>> in Debian was the prospect of a HAM specific version (which didn't
>> quite happen, since Bruce Perens & Bdale Garbee got busy with Debian
>> in general).
Yup, I did that. I did something like VMS -> Apple -> Windows ->
Slackware Linux -> FreeBSD -> OpenBSD -> Ubuntu -> Debian. I've had a
ham license twice and found that the technology and studying were more
interesting than most people you meet on the air. Hams talk about the
weather a lot. With the internet you can pick a topic and go there.
No matter where in the world they are or when they sent the message.
>> Also, the likes of this:
>>
>> https://events.ccc.de/2015/07/10/rad1o/
Now that's interesting, a computer dedicated to radio. I could google
and find pages like
https://www.rtl-sdr.com/a-new-hackrf-compatible-sdr-rad1o/ but you
can't actually buy one, you have to go to their club meetings. We're
seeing multiple generations of SDR. Getting cheaper too.
>> I know for instance that a decade or more ago Bdale was using SDR on
>> Linux (or at least talking about someone he knew, in which case Bdale
>> probably set it up) to record the whole amateur band in one go.
Yes, you can record a 2 MHz or so wide chunk at once if you can afford
the hard drive space.
>> All of which suggest that there's more than nothing going on in the
>> world of *nix SDR.
I meant GUI programs like HDSDR or Sdrsharp or gqrx. To see signals
on the screen as peaks in real time you need fast video almost like
Mplayer or omxplayer, you can't do that at a command line. You don't
have to turn a tuning knob and listen to everything to see what's out
there. http://ab1jx.1apps.com/pix/misc2/wx_channels.jpg It's more
like the difference between a tape drive and a hard drive.
> I have a couple of SDR USB Dongles that work pretty nicely out of the box
> with GNU Radio. The variant I have are from here
Yes, I have 3 of those, that's my entire SDR investment. GNU Radio
I've rarely had working, and it's big and slow requiring big fast
computers. Much is written in Python I think, it's not very efficient
for everyday listening. I'm talking doing GUI SDR on a Pi, qtcsdr's
about the only thing that qualifies:
https://github.com/ha7ilm/qtcsdr/archive/master.zip But it lacks some
features like being able to enter a ppm correction factor for your
dongle and I don't feel like learning QT so I can add it. It's a
trifle CPU-hungry too.
The ultimate GUI SDR for a Pi would involve the GPU for doing the FFTs
fast without tying up the CPU, and also use the GPU for the graphics.
But I wanted more portability, I'm actually working mostly under
OpenBSD and testing on a Pi.
For graphics I'm using XLib, nothing fancy. Fftw for the FFT. I'm
getting my IQ stream over tcp with rtl_tcp but I'm thinking of
changing to librtlsdr for more control, like being able to change
frequency ranges and gain. My latest adventures
http://ab1jx.1apps.com/pix/misc2/xsdr_hotiron1.png show my dongle's
getting clobbered with strong signals which cause spikes and false
signals, but I can't really turn down the gain with rtl_tcp. But I'm
learning SDR, in C, not in Gnuradio or matlab. And it runs at about
10% CPU on this circa 2002 i386 box. I'm not doing any demodulation
yet.
--
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