Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HTML_MESSAGE,RCVD_IN_DNSWL_MED,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: dmv.com: mailn 1095; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v4BDceh2009323 for ; Thu, 11 May 2017 15:38:41 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1d8oE9-0002fZ-E3 for rs_out_1@blacksheep.org; Thu, 11 May 2017 14:33:57 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1d8oE8-0002fQ-Ng for rsgb_lf_group@blacksheep.org; Thu, 11 May 2017 14:33:56 +0100 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1d8oE5-0005me-Hf for rsgb_lf_group@blacksheep.org; Thu, 11 May 2017 14:33:55 +0100 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id CCF8E20D5D for ; Thu, 11 May 2017 15:33:51 +0200 (CEST) Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 3wNvFq0Tf8z105n for ; Thu, 11 May 2017 15:33:51 +0200 (CEST) Message-ID: <5914683E.3000809@posteo.de> Date: Thu, 11 May 2017 15:33:50 +0200 From: DK7FC User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <579355A36AEE9D4FA555C45D556003AB8FDD90BF@servigilant.vigilant.local> In-Reply-To: <579355A36AEE9D4FA555C45D556003AB8FDD90BF@servigilant.vigilant.local> X-Scan-Signature: 69d86b33142413363dd56bd312139bf4 Subject: Re: LF: Some improvements in VLF Rx Content-Type: multipart/alternative; boundary="------------070601030308030501070600" X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.75 Status: RO X-Status: X-Keywords: X-UID: 11668 This is a multi-part message in MIME format. --------------070601030308030501070600 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Hi Luis, Am 08.05.2017 10:57, schrieb VIGILANT Luis Fernández: > 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 Yes the noise background is dominated by 'horizontal' traces, not by vertical traces, i.e. QRM (unwanted) instead of QRN (expected in a clean location). This domination is very expressed. So either your ground is hopeless contaminated or maybe something is even wrong connected? > 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 ? Are you using the BF862 as the first FET? I observed VHF oscillations in the past and would now suggest a ferrite bead as close as possible to the gate of the JFET. Are you sure the FET is working correctly? You can measure/calculate the drain current by measuring the voltage across the drain resistor. The TV coaxe is fine. What is the length (or better: estimated capacity) of the probe now and what is the height above the ground/roof/sourroundings? Did you try to use a bettery for testing the effect on the QRM? 73, Stefan --------------070601030308030501070600 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Luis,

Am 08.05.2017 10:57, schrieb VIGILANT Luis Fernández:
The VLF espectrogram has got clearer, but still contaminated. Specially at night, probably due to street led lights in the area
Yes the noise background is dominated by 'horizontal' traces, not by vertical traces, i.e. QRM (unwanted) instead of QRN (expected in a clean location). This domination is very expressed. So either your ground is hopeless contaminated or maybe something is even wrong connected?
 
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 ?
Are you using the BF862 as the first FET? I observed VHF oscillations in the past and would now suggest a ferrite bead as close as possible to the gate of the JFET.
Are you sure the FET is working correctly? You can measure/calculate the drain current by measuring the voltage across the drain resistor.
The TV coaxe is fine.
What is the length (or better: estimated capacity) of the probe now and what is the height above the ground/roof/sourroundings?
Did you try to use a bettery for testing the effect on the QRM?


73, Stefan

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