Raspberry Pi + RTL-SDR Working

First, I used parts of this gist by floehopper to set up rtl-sdr utilities on the Raspberry Pi (already running Raspbian with a 8 GB flash card at its disposal):

pi@raspberrypi ~ $ sudo apt-get update
pi@raspberrypi ~ $ sudo apt-get upgrade
pi@raspberrypi ~ $ vi no-rtl.conf

blacklist dvb_usb_rtl28xxu
blacklist rtl2832
blacklist rtl2830

pi@raspberrypi ~ $ sudo mv no-rtl.conf /etc/modprobe.d/

pi@raspberrypi ~ $ sudo apt-get install git-core
pi@raspberrypi ~ $ sudo apt-get install git
pi@raspberrypi ~ $ sudo apt-get install cmake
pi@raspberrypi ~ $ sudo apt-get install libusb-1.0-0-dev
pi@raspberrypi ~ $ sudo apt-get install build-essential

pi@raspberrypi ~ $ git clone git://git.osmocom.org/rtl-sdr.git
pi@raspberrypi ~ $ cd rtl-sdr/
pi@raspberrypi ~/rtl-sdr $ mkdir build
pi@raspberrypi ~/rtl-sdr $ cd build
pi@raspberrypi ~/rtl-sdr/build $ cmake ../ -DINSTALL_UDEV_RULES=ON
pi@raspberrypi ~/rtl-sdr/build $ make
pi@raspberrypi ~/rtl-sdr/build $ sudo make install
pi@raspberrypi ~/rtl-sdr/build $ sudo ldconfig
pi@raspberrypi ~/rtl-sdr/build $ cd ~
pi@raspberrypi ~ $ sudo cp ./rtl-sdr/rtl-sdr.rules /etc/udev/rules.d/
pi@raspberrypi ~ $ sudo reboot

Then, I added sox (to get the play command):

pi@raspberrypi ~ $ sudo apt-get install sox libsox-fmt-all

I hooked up a speaker to the Raspberry Pi audio port and then tuned and listened to Puget Sound’s favorite packet frequency:

rtl_fm -f 144390000 -M fm -s 12k - | play -r 12k -t s16 -L -c 1 -

Worked nicely. Need to add squelch argument and combine this with the demodulator I’ve been working on.  Satellite tracking with automatic recording of space station packets is the ultimate goal.

That Happy Moment When

the demodulator you’ve been working on starts outputting meaningful data instead of gibberish (T7RPUR WIDE1 WIDE2 are valid packet radio strings).

Screen Shot 2015-08-24 at 8.45.48 AM

I’m writing the demodulator in C++ and it uses the Goertzel algorithm.  Need to continue to flesh out the framer, and hook up STDIN to accept sound from rtl_fm and my new SDR dongle.

The goal: automated reception of Space Station packet radio, powered by Raspberry Pi.

Got My First Packet Through the Space Station

Screen Shot 2015-07-03 at 10.30.08 AM

I’m KF7APE.  At about 1726UTC on July 3.  Very excited!  Using a simple J-Pole antenna during a very close pass.  Can’t wait for new antenna to arrive to do even more 🙂

Call log courtesy ariss.net:

Screen Shot 2015-07-03 at 10.32.33 AM

Packet Radio Transmitter is Working

The mini DIN plug I needed arrived in the mail on Friday.  OMG such small pins to solder.  I really need to buy a proper magnifier.  Connected my Yaesu FT-7800 to the Pakratt.  Discovered that the USB interface is not (yet) recognizable by my MacBook.  Connected it instead to trusty old Trinity, an old PC of mine.  Also not recognized.  Downloaded drivers for USB serial port bridge.  Then it was recognized as COM9.

Hah!  Hyperterminal is no longer included with Windows.  So sad.  Found and downloaded it.  Installer looks like something out of 1992, but it worked.  Spent the next hour tinkering with the TNC settings, setting it to my call sign, adjusting the threshold so it actually received packets.

So. Much. Setup. Required.  No wonder most people don’t do this.  Such incredible barriers to entry.  That’s something I’d like to work to change.

Because it took so long to setup I missed an excellent space station pass, but managed to get my BEACON text set with my lat and long and was delighted to see my call sign (KF7APE) appear on aprs.fi as a result.


Now, I just need the Space Station to pass overhead again.  Patience required 🙂

For Want of a Mini DIN Plug

Picked up a packet modem today (an AEA Packratt 232 USB – thanks Rob!) – it will let me use the Mac to transmit to satellites and the space station – so I can do more than just listen.  But… I need a special connector for my radio, so I’m now patiently waiting for yet another small package to arrive in the mail.

When working with hardware, it seems there is a lot of waiting for small things to arrive in the mail. 🙂  I guess it’s the hardware equivalent of compiling 😛

And yes, I scoured the house for an old PS/2 keyboard to cannibalize, to no avail.

And yes, I’m totally going to use this to integrate APRS geolocation into a MapKit app on OSX.