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Re: LF: Re: Schumann in my garden

from [M0FMT] [Permanent Link][Original]
To: "[email protected]" <[email protected]>
Subject: Re: LF: Re: Schumann in my garden
From: M0FMT <[email protected]>
Date: Mon, 6 Oct 2014 11:21:39 +0000 (UTC)
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Hi all

Stefan, Thank you for the teach-in, very interesting. I am amazed even outside your city that the band is so clear. My experience in Saarland during my visits in the 2003-8 period was that just about anywhere I went I could hear the mains supply harmonics on the Hire car radio tuned to LW (I used to listen the BBC on 198khz). I can not remember anywhere in the UK where it was that "Bad". I always assumed it was the very high loading on your grid by a power hungry and burgeoning industry (never remotely experienced here of course) causing the wave form to become square......:-)

73 es GL Pete M0FMT IO91UX






Sent via my own personal Too-Way (two way) Earth Station to and from the Eutelsat Ka-band satellite  http://www.tooway.co.uk/  at approximately 172 degrees Azimuth in the Clarke belt owing to BTs 19th century cable technology inability to provide a good enough 21st century broadband service. I agree for this message to be passed on to BT Plc at 81 Newgate Street, London EC1A 7AJ  via the snoops at GCHQ Cheltenham, thank for your cooperation it is appreciated.


From: DK7FC <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Sunday, 5 October 2014, 23:10
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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