From: "Clemens Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <5908F9D1.7030403@posteo.de> <579355A36AEE9D4FA555C45D556003AB8FDD90BF@servigilant.vigilant.local>
In-Reply-To: <579355A36AEE9D4FA555C45D556003AB8FDD90BF@servigilant.vigilant.local>
Date: Mon, 8 May 2017 14:40:27 +0200
Message-ID: <DEEC4AE5DFCB445C92E482F5BF61F998@Clemens0811>
MIME-Version: 1.0
Thread-Index: AQHSx9kqLov3ejSO8ky0ZlWew2jd+6HqXfnA
Subject: LF: RE: Some improvements in VLF Rx
Content-Type: text/plain;
	charset="iso-8859-1"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Content-Transfer-Encoding: 8bit
Status: RO

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: owner-rsgb_lf_group@blacksheep.org 
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of 
>VIGILANT Luis Fernández
>Sent: Monday, May 08, 2017 10:58 AM
>To: rsgb_lf_group@blacksheep.org
>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: owner-rsgb_lf_group@blacksheep.org 
>[mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de DK7FC
>Enviado el: martes, 02 de mayo de 2017 23:28
>Para: rsgb_lf_group@blacksheep.org
>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
>
>