Hi Luis,
>Would it be better to use twisted pair
At this low QRG skin depth may become an issue.
The coax shield might be not thick enough.
So it's probably worth a try with twisted pair.
73
Clemens
DL4RAJ
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of
>VIGILANT Luis Fernández
>Sent: Monday, May 08, 2017 10:58 AM
>To: [email protected]
>Subject: LF: Some improvements in VLF Rx
>
>Hi VLF
>
>This weekend could fix the QRM problem with the VLF E-probe.
>There was a ground loop at the 1pps from GPS
>The ground of the GPS (and PC via USB) was routed to the audio
>transformer at the VLF signal side, not soundard side
>
>So, the noise was going up by the VLF cable to the probe and
>caused a 20dB noise rise in MF/LF in the nearby MiniWhip
>The VLF espectrogram has got clearer, but still contaminated.
>Specially at night, probably due to street led lights in the area
>https://ea5dom.ure.es/grabber/index.html
>
>I'm using a separate first Fet at the probe, connected by
>aprox 15m TV coax. Would it be better to use twisted pair or
>keep all the preamp up, close to the probe ?
>
>73 de Luis
>EA5DOM
>________________________________
>
>De: [email protected]
>[mailto:[email protected]] En nombre de DK7FC
>Enviado el: martes, 02 de mayo de 2017 23:28
>Para: [email protected]
>Asunto: Re: LF: SL settings for EbNaut FFT recording ?
>
>
>Hi Luis,
>
>Am 02.05.2017 22:51, schrieb VIGILANT Luis Fernández:
>
> The grabber is now showing full spectrum from 0-24KHz
> https://ea5dom.ure.es/grabber/index.html
>
>OK. There is still some room for improvements :-)
>
>
>
> The Rx is not at Benidorm in the high tower. It is in
>the roof of a two level house on top of a 5m pole
> But clear out from high obstacles and trees
>
>On top of a 5m pole is very good. But the location or earth is
>very contaminated.
>
>
> The pole is a 50cm x 10mm diameter aluminium rod. Will
>play with the 10MOhm resistor and first fet stage
> with filter.
>
>I think this is not necessary now. Better to try to find a
>cleaner ground and/or location, as you say.
>
>
> The noise at MiniWhip rised 20dB, so must get it
> appart to keep the ear at MF/LF.
>
>Yes, LF and MF stays important too! :-)
>
>
> The power supply is a 12V transformer shared with the MiniWhip
>
>Maybe this causes a ground loop which picks up the hum. Could
>explain why LF/MF became worse as well.
>
>
> Will test another one just for the VLF probe and with
>better filtering.
>
>Or try a battery in a first step and see the difference. A
>separate small transformer supply is certainly a good decision.
>
>
> The GND of the antenna is separated
> from mains earth and there is an audio transformer to
>the PC soundcard
>
>FB.
>
> BTW. What I'm getting from SL is one FFT file 112Kb
>size every hour as Markus said
> But how can I merge all the files of a 8h transmission
>like the one your are running now ?
>
>Each file covers 8.9 hours. They are just overlapping so that
>you can select the closest one (lowest start time offset). I
>don't know the exact settings though. I would recommend to set
>the FFT center frequency to 8270.1 Hz.
>
>
>
> Your signal in your grabber looks stronger than the
>previous transmissions
>
>It is the same antenna current though.
>
>73, Stefan
>
>
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