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VLF: Carrier on 4470.005 Hz! - Reception in France

To: [email protected]
Subject: VLF: Carrier on 4470.005 Hz! - Reception in France
From: DK7FC <[email protected]>
Date: Mon, 18 Sep 2017 00:56:48 +0200
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Am 31.08.2017 22:37, schrieb DK7FC:
This weekend i will be in France again, JN29OD96SK , on a field day with the radio club. I plan to receive the 4470 Hz signal with a small loop and its new preamp and the octo soundcard. Thus i want to run a carrier again on 4470.005 Hz. Tomorrow, Friday, i will transmit the EbNaut message again. After that, the carrier will continue until sunday. With some luck i hope you can decode the message when including the friday transmission. If not, i could continue to transmit on monday...

It took some time but now i have some results from that experiment. I actually placed a 84 turn loop with 0.8 m diameter and a low noise preamp between some trees in France, JN29PD06BO.
A path of 250 km or 3.7 wavelengths between RX and TX ( ). Quite a compact RX system for VLF. I did not prepare the experiment as good as possible, there was no E field RX together with the loop. H field only. It was mainly another test of the octo-soundcard and a first test for the samll loop and its LNA.
I converted the data files recorded by vlfrx tools into a wav file and analysed it in SpecLab. Here is a wideband spectrogram showing the QRN: (time markers are incorrect there)

On sunday morning, 3rd Spetember when i looked at the installation i found that the preamp was disconnected from the battery. It must have been an animal walking arround into the field, stumbling over the cable ;-) . Fortunately the interruption took just about one hour ;-)
Assuming that vlfrx tools correctly resampled to 24 kS/s i run the file into SpecLab set to 47 uHz FFT bin width, hoping to see a trace/peak at 4470.005 Hz.
And indeed, there is something! See attachment. That's a first trace from DL to F on the 67 km band :-) About 18 dB in 47 uHz during the best time, much more than i expected.

Another success is that i managed to produce a first spectrum peak and generated a png file using vlfrx tools. The procedure is based on Paul's advice. :-)

73, Stefan

Attachment: 4470_47uHz.png
Description: PNG image

Attachment: 4470plot.png
Description: PNG image

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