Laser-cut RPi case

It’s a bit de rigeur, but after finishing some etching last meeting, and with a bit of time left, we cut an RPi case in 3mm acrylic.  The design is from Adafruit, and has the nice feature of snapping together, with no bolts, screws, or glue required!

Aside from one miss where one letter from one label was cut instead of etched, it came out quite well.  This was I think £3 of material and £2 of cutting time on the laser.

SDR flowchart: POCSAG

Not sure any of these are entirely working, but the local area doesn’t appear to use POCSAG but has maybe gone onto FLEX as the frequency bands look a bit busy.

Simplest attempt is using a modified version of osmo-pocsag.  It writes out baseband to a file.  Create a fifo, and direct the the cmdline app to its output.
A more complex version is based on this (by bafe), and has some good waterfall pictures to give a better indication of what’s going on.  Confusingly it’s called gr-pocsag, and thus confusable with the POCSAG decoding GRC block by patchvonbraun here, which needs compiling and installing.
I’ll update this once I’ve actually either confirmed that what I’m seeing is not POCSAG or which/either/both/none works.

Playing with the RTL SDR

So the hackerspace will imminently have a number of Realtek-based SDRs as demonstrated last meeting.  An SDR, or Software-Defined Radio is a very flexible device, that performs the equivalent of a “raw recording” of a portion of the RF spectrum and then the raw samples can be processed in any way you like on your computer.

So for example, you can pick up FM radio, the pager network, transmissions from the ISS, or aircraft transponders.  Working GRCs will be posted on the blog
We’re going to try doing some of these things in the space over the next few months, the exact dates will be discussed on the list.  If you’d like to try this, here’s some links:

Another useful resource is the subreddit for it.