Airband is used by planes to communicate with the ground. Given I live near the Helsinki airport, I’m in a prime location to receive those properly.
For instance, here is small compilation of recordings:
Do note listening to airband might be illegal in some countries, for instance, Germany or North Korea. Always check your local laws (though unenforceable).
Just yesterday, I received my HackRF PortaPack. The HackRF is basically an SDR, or Software-Defined Radio, that allows you to plug it to a computer and have a nice spectrum view of everything (amongst other things).
While the PortaPack integrates its own screen, battery and everything, I find it more convenient to connect it to my computer and use it that way. I can record more easily, have a larger view thanks to my monitor, etc, etc.
First thing I did was to update the firmware. Luckily, it’s really easy to do so, I just had to download the latest version of Mayhem, put it on a micro-SD card, use the internal flash tool, and done, all up-to-date.
Now, a lot of sellers will try to give you some SDR software to use with the HackRF: don’t listen to them. Instead, try SDR++, a Free and Open-Source SDR software, with built-in support for the HackRF. Added bonus: it’s even in the Fedora repositories! As a side note, you might need to add your user to the dialout group before starting to use it.
Once you have SDR++ installed, just head to the top right, in the “Source” section, in the scrolling menu select “HackRF”, and right below, select your HackRF (there should only be one).
Right below, I can recommend setting both the “LNA gain” and “VGA gain” to something like 16, it’ll make sure you can actually hear anything.
Other settings I can recommend tweaking a bit are within the “Display” section, near the bottom on the right. Do note those settings are my own preference:
FFT Hold: enabled, 60
FFT Framerate: 40
FFT Size: 524288 (this avoids having the waterfall look “blocky” when zooming in, but has a performance cost when de-zoomed)
FFT Window: blackman
Color map: WebSDR
Those settings basically reproduce the WebSDR look and feel that I’m used to (for instance, from the Twente WebSDR).
Now time to listen! To make things better, I can also recommend playing with the “Squelch” option. You might need to tweak this differently based on which frequency you want to listen to.
In any case, have fun listening to whatever you can find!
Last Thursday, while being at the radio club OH2K, I built a Pixie radio kit V3 (generously given to me by one of the regulars).
The Pixie radio is a low-power (about 0.4W when we measured), morse only radio that can only operate in the 7MHz (or 40 meters) band. Its main appeal is that you can build it from anywhere from €2 to €5, which makes it a really easy option to get.
The finished thing looks like this:
Given it was my first time building such a thing, it took me around two hours to build. It took that long because I mistook some components for others, and had to de-solder them.
Another issue I ran into was when using it at home. This board takes between 9V and 12V of power, so naturally, I fed it using my switchable power supply.
That’s where the first error came in, this introduced so much noise I thought the board broke during the transport from the club to my place.
Luckily, lazily soldering a wired barrel jack connector to a 9V battery solved the issue, and at night, I can hear really, really faint morse code in the background.
I’ve tried transmitting a bit, but so far, no response yet. I think it’s going to be hard getting anything out of that thing given my conditions aren’t close to ideal either (densely populated area).
I’ve also ordered a V4 board on AliExpress to see if it’s any better (but given the simplicity of the board, I doubt it). In any case, it’ll make for good soldering practice.
While listening to a WebSDR yesterday, I managed to catch a numbers station transmitting a message.
This was recorded at around 19:03:00 UTC, on 7317.0kHz
Looking around, this station seems to be named E11 “Oblique” and is apparently one of the most active. It is operated by an unknown agency, broadcasting from Warsaw.
I didn’t manage to record the whole message, but a good part is there, you can hear a group of numbers being started using the word “ATTENTION”, repeated multiple times.
From the documentation available on Priyom, this is the second part of the message, the first part being a three-digit ID, the word “oblique”, then a count, all of this happening over the course of around three minutes.
The full transcription of what I got (this may contain some errors):
A friend sent me a link to an interesting blog post talking about making an Open-Source DMR radio using a LimeSDR board and GNU Radio.
Digital Mobile Radio (DMR) is a mobile radio standard created by ETSI, which is very popular within the amateur radio community. […] A very basic DMR modem (receiver and transmitter), capable of voice calls, that could emulate a subscriber radio using a SDR transceiver as the radio interface is described in this page. While this modem is just a proof-of-concept interpretation of the DMR standard with no real use-case, there exists at least one open source project which proposes to create an open source DMR transceiver.
