On a sunny day (Wed, 10 Mar 2021 11:56:46 +0200) it happened Tauno Voipio snipped-for-privacy@notused.fi.invalid> wrote in <s2a54v$po4$ snipped-for-privacy@dont-email.me:
So did not get around to it yesterday, but his morning put one xpsa rtl-sdr spectrum analyzer on 1,350,000,000 Hz and an other one on 1,374,576,000 Hz. those seems to be the start and end space they use.
The top xpsa looks at a 2048 kHz wide band at 1,374,576,000 Hz and the lower one at a 2048 kHz wide band at 1,350,000,000 Hz
2048 kHz is the widest band I can look at, 2048000 sample rate for these rtl-sdr sticks, 4096000 it does not accept... ??Recording is just screen capture with ffmpeg -f x11rab -s 1906x1070 -r 60 -i 0:0 -y radar.mpeg And then edited for length.
So may well be digital but for sure they are sending very complex signals.
Will think about it a bit....
Could listen to it on the radio, aha! I see how the modulation has changed during the sweep from the lowest to the highest frequency or during rotations.
But how does it sound, for example on an AM radio? # listen to the radar with rtl-sdr in AM mode (using alsa hw:1,0 change for your audio): rtl_fm -d 0 -f 1350000000 -M am -p 0.0 -s 24k | aplay -D hw:1,0 -t raw -r 24000 -f S16_LE -c 1 -
# to record the radar using AM demodulation as wave file: rtl_fm -d 0 -f 1350000000 -M am -p 0.0 -s 44.1k | sox -t raw -r 44.1k -e signed-integer -b 16 -c 1 - radar_am_sound.wav
# to make it into a shorter mp3 file: lame radar_am_sound.wav radar_am_sound.mp3
You can download it here:
Now we all know trained birds have been used in wars.... Pigeons Hawks... But so if you hear a bird (animal I mean ;-) on the radio beware, it may be a radar station.
The USB, WBFM and FM demodulation did not give such nice signals. I did notice the in hearing range AM sidebands in a previous post I think, but much of the modulation part may well be above human hearing range.
And digital? I think not now. But could be.