Reminder: First BAA VLF (SID Monitoring) meeting 16 March 2026 @ 20:00 UTC
andrew....@googlemail.com
Welcome to everyone, whether you are member of BAA or not – everyone welcome – regardless of experience level – come and tell us about your setup and discuss any issues or advice you have for others.
It does not matter if you have never done any VLF monitoring in past – still come!
The meeting will be recorded and available to watch on the BAA Youtube channel by end of the week.
Andrew
LOG IN DETAILS FOR MEETING BELOW:
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Microsoft Teams meeting
Join: https://teams.microsoft.com/meet/357127117415?p=HsB0ITEukhGEDeLGBK
Meeting ID: 357 127 117 415
Passcode: 4mh9we9A
Dial in by phone
+44 20 3321 5208,,453456086# United Kingdom, City of London
Phone conference ID: 453 456 086#
Franck Durand
The recording system consists of a triangular antenna insulated from the ground, with the top point at about 8 m and the base at 20 cm above the ground or square 1,2m x 1,2m at 1,5m from the ground. The connection is made at the center of the base of the triangle using a ferrite transformer made of TDK N30 material purchased from TME (https://www.tme.eu/fr/details/b64290l0038x830/anneaux-de-ferrite/epcos/) with the reference B64290L0038X830. The properties of this ferrite toroid are AL = 7000 nH.
Around this ferrite core, I carefully wound 25 turns of copper wire for the primary and two windings of 54 turns each for the secondary. This toroid was not originally intended for this application but for building another differential preamplifier based on matched SSM2212 transistors configured in common-base with the emitters as the input. This is the reason for the double winding with a center tap, which will not be used this time since the preamplifier is not yet ready. The two output windings are therefore connected together in series to form a 108-turn coil.
The output of the toroid is connected to the sound card and the digital recorder using a coaxial cable, normally as short as possible but long enough to allow sufficient distance from the antenna to avoid introducing electromagnetic interference, particularly the 50 Hz from the house electrical system. In my case there was still about 30 m of low-loss 10.3 mm coaxial cable of the Hyperflex-10 type.
The sound card used is a U-PHORIA UMC204HD, set to a sampling rate of 96 kHz / 16 bits.
Here some link (most in French) to presentations en vidéo I've done for public in our Ham radio associations, this could be useful.https://franck.aquarelles.org/wp-content/uploads/2022/04/Onde_Expo_VLF_F4IEW_V8.pdf
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Conférence ELF VLF à L’ARAM 95, 14/02/2020
https://franck.aquarelles.org/wp-content/uploads/2020/02/aram95_VLF_F4IEW_V8.pdf
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« Un voyage sur Terre à la découverte des mystérieux signaux radio naturels » De l’enregistrement à l’écoute de la musique des aurores boréales …
Une conférence accessible à tous (enfants et adultes) animée par Franck Durand,
https://aram95.r-e-f.org/wp-content/uploads/2023/07/Conference_signaux_radio_naturels.F4IEW_V1.pdf
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Récepteur ELF-VLF DARJEELING V.2.1. de F6AGR, tests and measurments by F4IEW
https://franck.aquarelles.org/wp-content/uploads/2020/01/Essais_mesures_Darjeeling_V2_1_F4IEW.pdf
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YouTube:
Les très basses fréquences (TLF-ELF-VLF), qu'est-ce que c'est ?
https://www.youtube.com/watch?v=jfkgoobsSxw
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YouTube:
Un voyage sur Terre à la découverte des mystérieux signaux radio naturels
Part1:
https://www.youtube.com/watch?v=q04NjeDdP1I&t=4s
Part2:
https://www.youtube.com/watch?v=ASfytpGAaiE&t=17s
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