The receivers
A Sangean ATS-909X2 for listening at the dial. Since the autumn also an SDR receiver, an SDRplay RSPdx-R2, which records the whole mediumwave band — two million samples a second — so that every channel can be listened to afterwards.
The antennas
At Skeppevik a KAZ: a 20-metre terminated loop in the grass, aimed at North America. Measured against European transmitters in known directions, it suppresses what comes from behind by about 20 dB. There is also a Tecsun AN-200 and an active loop, a Bonito MegaLoop FX, which can be turned — it also goes on the balcony in Karlskrona.
The recording
A night becomes a few hundred gigabytes. Once it has been gone through, only narrow strips around what was interesting are kept, along with the originals of what was logged.
The carrier as a fingerprint
Every transmitter sits slightly off its channel, often by only a few tenths of a hertz. The offset follows the transmitter night after night. A book of thousands of such carriers lets the computer say «this is the channel's usual one» or «this is new» — a clue, never an ID.
The time
The recording drops half a percent of its data at a steady rate, and the clock drifts. The time signal on the hour — six pips, the last one on the second — locks it again, so that a voice can be found to the second.
Speech recognition
Whisper, an open speech-recognition model, listens to selected pieces and looks for station names, towns and frequencies. Pieces in other languages are translated into English next to the original. It suggests; it never decides.
The app
An app of my own on iPad and Mac, built during the autumn together with Claude. The log, the forecasts, the reports and the morning's review live there. This site is built from the same log.