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Re: LF: Also EA in VLF soon?

To: [email protected]
Subject: Re: LF: Also EA in VLF soon?
From: DK7FC <[email protected]>
Date: Wed, 13 Apr 2016 14:57:22 +0200
In-reply-to: <[email protected]cal>
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Hi Luis,

Am 13.04.2016 12:21, schrieb VIGILANT Luis Fernández:
This is getting too fast, isn't it ? ;-)
Hehe, i know what you mean ;-) But it's just the first step, receiving!

Living in a 26th floor, my main enemy and at the same time my best friend is the elevator :-)))
The motor variators using three plase 380V are very noisy.
My VLF-grabber is living on a 6th floor building (35m AGL) and we have 2 elevators. I am sure they run at 400V 3-phase.
Specially from DC to 10MHz
This is the question! I wouldn't expect it is a white noise from DC to 10 MHz. There are band regios where no QRM can be found and others which are massively contaminated.
You have to see, and this is why it makes sense to check that before.

I have been trying to fix this even with the help of the lift maintenance company, but it is impossible.
I bet it is not impossible :-) Did you insert a 3 phase mains-filter network and avoid unwanted ground loops and other EMC problematic stuff? Maybe it is not necessary to do that work when receiving below 10 kHz.
 I have my antennas just on the roof cover of the
lift motors and controllers cabin. The variators include all the standar ferrite "filters" but can't fully solve the problem. It would probably need a matched
filter, not a standar "plug&play" but this things are under professional control and can't be touched without risks
I understand.
That's why I keep my Rx at 9km in a different QTH. There is a MiniWhip there and a Perseus SDR
My plan for VLF is to connect the MiniWhip directly to the sundcard of the PC.
Yes, exactly, that's the way. You could simply use a second mini-whip, with some minor modifications maybe. A audio decoupling transformer could help to avoid QRM too.
Would you install a VLF grabber from there, frequently uploading spectrograms generated in SpecLab? I could help you with any problems.

A resistive splitter for the MiniWhip is what I have in mind for that
Perseus works down to 10KHz but not lower
The soundcard is the best choice!
Once you get "hands on work" with the coils, just imaging how big coil will I need for VLF gets me sweat :-)
But knowing the very good performance of the low bands here at 80m height that will really worth the effort
Ideas wellcome !
For a first impression i would definitely focus on RXing on VLF first. And don't forget to transmit on LF! :-) We are waiting for your signal there :-)
I have updated my OPDS32 list and i'm watching all the time now. BTW the groundwave range on 2200m is about 800km in daytime, so there are chances. If you can, just run the TX through the night :-)

Luis, i found a stereo sound system today in the trash bin. I works well! I have coupled my VLF generator to it and it produces a perfect sine wave. Also i successfully transformed the power to a voltage of 220V rms, which is the level that i need to run the maximum allowed power to my antenna incombination with the yoghurt coil :-) Soon i will radiate some power on VLF again. Maybe soon means today!

73, Stefan
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