Author Archives: widget

SDR flowchart: POCSAG

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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

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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.

Minimus workshop #1

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Monday was a good day for hacking; we had an impromptu Minimus workshop.  This was surprisingly successful, attendees were able to get their boards programming in Windows or Linux as to their preference, and then start diving into code.

The devices aren’t as friendly as the Arduino boards, and the example source code will compile but not always run without extensive tweaking, but by the end of the session, in addition to a medley of flashing lights, we also had a one button keyboard and a virtual serial port that reported its button state.

Due to demand we will run another of these in April (2nd or 16th, TBC) and again will have Minimus boards available for use on the day or purchase.  There’s no fixed cost for the workshop, but donations are appreciated.  If you have a Minimus board or are interested in a step on from Arduinos, why not come past?

As a reminder to Northackton members who are also NSME members, their auction is on the 13th of March.

Layzor cutting

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On Monday we visited Martin’s laser cutter, as once he installed it at his house with a water tank for cooling, it’s not particularly mobile.  He showed us some of the many things he’s made for his blog, and his lightbox for photographing them.

Onto newer things, we printed a NortHACKton stamp for visiting passport-holders.  After learning how to etch rubber, I then provided an object lesson in the power of cyanoacrylate glue by adhering to the stamp rather effectively.
Secondly I had made an SVG of a bokeh rig for my camera for Martin to convert and cut, which produced a passable first attempt at a kit that can fit to my D3100.  Not all of the pictures were good, but it was certainly a learning experience.  See Martin’s blog for the design, and the results are here, in the February pictures of this set.
March’s meetings – we meet in the space as normal for Monday 5th, and on the 19th there will be another pinball evening in Bedford.  See the mailing list for more details.

Hackerspace Passports Accepted Here