blinry
25 & 26: See ionosondes and radar signals
In the low frequencies, occasionally, you can hear a short *chirp*! :D These are caused by ionosondes, scientific instruments which measure the properties of the ionosphere by sweeping a wide frequency spectrum.
Another signal (which I accidentally got in the same screenshot) is a radar system – in this case, according to the Signal Identification Wiki, it's a "CODAR" system, used to measure the motion of water waves and currents along coasts! :O
blinry
24: Detect whether your notebook is charging
As I'm browsing the very low-frequency bands, I had a strange problem: Sometimes, that would work okayish, sometimes I could even make out voices!
Other times, it wouldn't work at all, and everything would be loud noise. Even in regions where I had better reception before!
Just now, I found out how to solve that issue – by unplugging my notebook charger. D'oh! :D
blinry
23: Receive digimodes from other countries
I found some other strange signals on the 30-meter band. The Signal Identification Wiki was really helpful for figuring out what they were: https://www.sigidwiki.com/wiki/FT8
FT8 is a new protocol, invented in 2017, and it seems to be super popular right now! It allows you to transmit short messages, and again, people are looking for people to talk to (CQ), saying how well they receive each other, or saying goodbye (73).
This is the WSJT-X software.
blinry
22: Receive maritime weather reports
The German Weather Service broadcasts maritime information throughout the day on various shortwave frequencies.
They use a protocol called RTTY (radioteletype), and it took me a while how to decode it. But I found a neat little program called "fldigi": You can pipe audio to it, and then if you pick the correct settings, it happily transcribes the messages!
Here's the station weather reports for the Baltic Sea and Northern Sea!
blinry
21: Receive Morse code from other countries
On the 30-meter amateur band, I found people sending Morse code! :O
I've been learning it a little bit, so if I record it and slow it down, I can understand it: They're sending their callsigns.
These are from Belgium, France, and Italy! \o/
I compared to my 2-meter dipole antenna, and the reception is definitely better – I can pick up more transmissions, and with much less noise!
blinry
...and draped it all around my room!
People on the Internet say that there are many problems with this – that it would be better to have it outside, and that there's an impedance mismatch between the receiver and the wire.
I could address those problems, but I wanna try how well this works first :)
blinry
...directly attached it to the center of another SMA connector...
blinry
This is going to be a simple "random wire" antenna, to allow me to get better reception in the lower wavelenghts, which I've omitted so far.
I've measured out 21.6 m of wire (which for ✨magic✨ reasons seem to be a good universal antenna length)...
blinry
Good morning! Let's build an antenna!
blinry
20: Receive amateur packet radio
In the 2-meter amateur band, there are certain frequencies for the "Automatic Packet Reporting System". It's a bit like IP – packets have a "from" and a "to". They can also broadcast their position, or weather data.
Some stations seem to announce themselves as repeaters, which probably help forward the packets to increase the range.
And two people seem to be on a "fieldday", and broadcast their location. :D
SDRangel can create a map automatically:
blinry
Some pictures from the landing site!
And I think I have earned this:
19: *Hunt* weather balloons!
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