[Aavso-sid-list] Software longwave receiver

[P. W. Schnoor]

Dear Fellow Observers,

Playing around with a new sound card (M-Audio, Audiophile 192)
I'm testing the autonomous creation of "waterfall spectra" from
4.0 KHz up to 96.0 KHz over time. The signal strengths are coded
as colours. Examples: http://home.arcor.de/df3lp/spec/
updated in 30 min. intervals. Resolution: 1000x1200 pixels.

Some technical details:
-Antenna: ferrite coil l=20cm, nulls at 240/60 deg.
-Preamp: OP27 low noise operational amplifiers.
-Transfer to sound card input: Cheap video/audio transmission
  system from supermarket, 2.4 GHz, using the video channel(!).
-Channels at VLF/LF: 4096, 3830 presented, each ~23.5 Hz of
  bandwidth.
-Dynamic range:  >60dB (>100 dB at sound card).
-Computer: Pentium III/450 MHz (bored...).
-Data acquisition system load: ~5% average.
-Software: modified SIDD 0.93 from Paul Nicholson, UK
  and some homemade Python code for graphic and upload.
-Operating System: Linux, sound: OSS (ALSA does not work well
  with the Audiophile 192).
-Spectral averaging: 5 min.
-Data volume: >100Mb per diem. (Hmmm...)

The strongest transmitter is 23.4 KHz (German Navy) received via
the 240 deg. "antenna null". Clearly visible are several navy
signals from UK, French, Italy and time code transmissions from
Germany, UK, and Switzerland. Signals from Puerto Rico, USA and
Russia have been detected over night. Some signals are not
identified yet. Beyond 88 KHz the splatter from LORAN-C (100KHz)
appears to be prominent. Unfortunately some wireless 
thermometers are present on the 2.4 GHz link, so I will
switch back to ordinary wire transfer between antenna block and
sound card in the near future.

Keep in mind that this is a testing phase so all parameters may
vary...

Greetings from North Europe,
Peter