clear skies! (created 05-30-1999; modified 09-11-1999)
New unexpected results of
VLF/ELF-monitoring
antenna located at D64354 Reinheim/Georgenhausen - E 8°48'14'' N 49°50'50"
A question to all of you:
During an experimental setup of a capacitive pickup made of a circular Al-plate with a diameter of approx 10 inches, placed 6'' above a rectangular shaped ground plane (steel) just on the ground (15m in front of my house) i noticed many strange and unknown signals like that one below. The modification was done with my active electric antenna (i normaly prefered a 2.5m pole-antenna for horizontal E) to increase the sensitivity in vertical polarised E-Field VLF/ELF-signals. Immediately i change the input back to the pole - and no 'strange' Signals could be heard further on. So i turned my pole horizontally - keeping a small distance to the ground (5'') and the unknown Signals appeared again (spherics with highter frequencies and the humm of the powerlines vanished in this case). I resume that the shape of the antenna could be very variable but it must be positioned near the ground and oriented for vertical polarisation (highest capacity against ground). The intensity of this signals is remarkable. It exceeds the residual humm of the powerlines in my suburbane region by a factor of 10 and more. It seems that the activity is highter at daytime and low at night. I thought for the first time that birds, insects or other mechanical exitations of the plate are the reason of this 'ringings'. But the modified pole antenna shows its electrical origine (covered with PVC it could not ring). The center-frequency of the example was approx. 275Hz. Other events appeared in the range of 30Hz up to 500Hz with a single (another event is shown here), double or (very rare) triple peak with short duration (<=secs). Attack and decay could be very variable also. The maximum rate during my observations was hight as 30/h after hight noon 'til sunset and low as 1/h at nighttime. If anyone got a good idea to explain this effect or knows something from his own personal experience - please let me know.
Thanks for all responses
Hans Guenter
Fig. 1 Spectrogram of an insects signal
(275Hz)
Fig. 2 and in the frequency
domain
unknown2.wav (80k)
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