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Stefan,
very fine result, well worth the
effort!
73, Markus
Sent: Monday, October 06, 2014 12:10 AM
Subject: LF: Re: Schumann in my garden
PS:
Another link :-) The file https://dl.dropboxusercontent.com/u/19882028/VLF/VLF%20Garten%20in%20T%20Antenne%2005102014_2nd.WAV
(576 MB) You can test your sound system by listening to the 16 2/3 Hz stuff and
ELF sferics :-)
Am 06.10.2014 00:06, schrieb DK7FC:
Hi ELF und sub-ELF
fans,
I have to report about very good success on reception in the
ELF and sub-ELF range. This evening arround 16 UTC i successfully
received 5 Schumann resonances with my T antenna in the
garden in 8m above ground, 400m outside the city.
I significantly
improved the circuit:
Higher input resistance, now 100 MOhm
Lower
cut off frequency using a 3 stage LPF arround 3 kHz
also a lower cuf off
frequency of the high pass now below 10 Hz
Removed the electronic parts
from the breadboard and re-soldered them on a copper board. This was
essential! because there were undefined conducting layers on the breadboard
which affected the working point of the JFET.
New preamp: https://dl.dropboxusercontent.com/u/19882028/VLF/20141005_162621.jpg
New
schematic: https://dl.dropboxusercontent.com/u/19882028/VLF/DK7FC%20ELF%20preamp%20V2.jpg
Results
(shown without sferic blanking)
wideband 0...24 kHz: https://dl.dropboxusercontent.com/u/19882028/VLF/NewELF_wide_10s_1.46HzFFT.png
also showing the frequency response of the circuit
0...1 kHz: https://dl.dropboxusercontent.com/u/19882028/VLF/NewELF_0to1kHz_10s_1.46HzFFT.png
0...55
Hz: https://dl.dropboxusercontent.com/u/19882028/VLF/0...55Hz_5sperdiv_45mHzFFT_garden3rd.png
ZEVS:https://dl.dropboxusercontent.com/u/19882028/VLF/ZEVS_garden3rd.png
(not so strong this time. QRN?)
What about these sferics below 2 kHz?
Is it normal that they are so strong? Or is it a technical problem? Can i
improve the situation by harder attenuating the spectrum above 2 kHz? At least
this is what i want to try.
Next ideas for improving the SNR of
ZEVS and Schumann:
Increasing the R of the LPF to 2.2...3.3 MOhm
Maybe
trying 1 GOhm for biasing the JFETs gate to 6V
Improving the insulation of
the antenna feeds (simple cord now, without ceramic between).
Trying to
rise the antenna 1 meter
Fixing the feed point by a ceramic
insulator
73, Stefan/DK7FC
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