Return-Path: X-Spam-DCC: paranoid 1170; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.4 required=5.0 tests=BAYES_00,HTML_40_50, HTML_MESSAGE,RATWARE_GECKO_BUILD autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id s93JfoEG030157 for ; Fri, 3 Oct 2014 21:41:51 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Xa8gD-0007MI-2D for rs_out_1@blacksheep.org; Fri, 03 Oct 2014 20:38:17 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Xa8gC-0007M9-NO for rsgb_lf_group@blacksheep.org; Fri, 03 Oct 2014 20:38:16 +0100 Received: from relay.uni-heidelberg.de ([129.206.100.212]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.82) (envelope-from ) id 1Xa8gA-0003xL-Dr for rsgb_lf_group@blacksheep.org; Fri, 03 Oct 2014 20:38:15 +0100 Received: from crusoe.iup.uni-heidelberg.de (crusoe.iup.uni-heidelberg.de [129.206.22.248]) by relay.uni-heidelberg.de (8.14.1/8.14.1) with ESMTP id s93JcCAx005554 for ; Fri, 3 Oct 2014 21:38:13 +0200 Received: from [129.206.22.206] (pc206.iup.uni-heidelberg.de [129.206.22.206]) by crusoe.iup.uni-heidelberg.de (Postfix) with ESMTP id A7CD7E1493 for ; Fri, 3 Oct 2014 21:38:12 +0200 (CEST) Message-ID: <542EFB24.5010300@iup.uni-heidelberg.de> Date: Fri, 03 Oct 2014 21:38:12 +0200 From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= 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: <54281B0D.4040202@gmail.com> <1FEF5D3CDFAF4F5D9A31B0134D133FCF@White> <54296984.7080607@gmail.com> In-Reply-To: <54296984.7080607@gmail.com> X-Scan-Signature: fce77e88417377663dedf94f027ec622 Subject: Re: LF: ZEVS RX ant question, now success Content-Type: multipart/alternative; boundary="------------040707000507060709060202" 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 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 594 This is a multi-part message in MIME format. --------------040707000507060709060202 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Hi VLF, This evening i received ZEVS for the first time in the garden :-) I used nearly the same circuit than in my email below. However, i found that the J310 was damaged! Remembers me on the old discussion if protecting diodes are necessary or not :-) But this is a large antenna, compared to an active E probe like the PA0RDT-antenna... Now i've replaced the JFET and added two 4148 protecting diodes on the gate against ground and plus. Reception looks much better now: 0...24kHz: https://dl.dropboxusercontent.com/u/19882028/VLF/wide_500msperdiv_732mHzFFT_garden3rd.png 0...4 kHz: https://dl.dropboxusercontent.com/u/19882028/VLF/0...4kHz_500msperdiv_732mHzFFT_garden3rd.png 0...500 Hz: https://dl.dropboxusercontent.com/u/19882028/VLF/0...500Hz_500msperdiv_732mHzFFT_garden3rd.png ZEVS in 7.6 mHz, 40 sec scroll rate: https://dl.dropboxusercontent.com/u/19882028/VLF/ZEVS_1st.png It looks like i need some more gain on the lower frequencies. Will modify the circuit a bit... 73, Stefan/DK7FC >> >> *From:* DK7FC >> *Sent:* Sunday, September 28, 2014 4:28 PM >> *To:* rsgb_lf_group@blacksheep.org >> *Subject:* LF: ZEVS RX ant question >> >> HI VLF, >> >> Yesterday i tried again to receive ZEVS. I didn't know if it was on >> air but gave it a try. Recorded about 2 hours of the VLF spectrum >> received on my T antenna (i.e. E-field). I also used a source >> follower (J310) but added a 3 stage RC filter in front of the gate. I >> thought i can afford some pF against ground now with the relatively >> large antenna which must have about 150 pF. I used this circuit: >> https://dl.dropboxusercontent.com/u/19882028/VLF/ZEVS%20test%20ant.jpg >> >> But somehow the spectrum looks not as expected. While the MSKs are >> still strong, there is much noise below 2 kHz and the sferics appear >> to be quite weak. See: >> https://dl.dropboxusercontent.com/u/19882028/VLF/Garden%20T%20antenna%20VLF%201.png >> >> I remember from tests with a small active antenna for VLF, where i >> used 100 MOhm resistors on the gate, that *charged humidity *caused >> much noise. >> Could this be the same effect here? >> Should i try to use a lower input impedance of the preamp? >> Maybe you remember, there were certain transistors, several decades >> ago, they were called bipolar transistors, NPN and PNP. Maybe i >> should try one of them? :-) >> >> Advice is apprechiated. Where are the experts? >> >> 73, Stefan/DK7FC --------------040707000507060709060202 Content-Type: text/html; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit Hi VLF,

This evening i received ZEVS for the first time in the garden :-)

I used nearly the same circuit than in my email below. However, i found that the J310 was damaged! Remembers me on the old discussion if protecting diodes are necessary or not :-) But this is a large antenna, compared to an active E probe like the PA0RDT-antenna...
Now i've replaced the JFET and added two 4148 protecting diodes on the gate against ground and plus.
Reception looks much better now:
0...24kHz: https://dl.dropboxusercontent.com/u/19882028/VLF/wide_500msperdiv_732mHzFFT_garden3rd.png
0...4 kHz: https://dl.dropboxusercontent.com/u/19882028/VLF/0...4kHz_500msperdiv_732mHzFFT_garden3rd.png
0...500 Hz: https://dl.dropboxusercontent.com/u/19882028/VLF/0...500Hz_500msperdiv_732mHzFFT_garden3rd.png
ZEVS in 7.6 mHz, 40 sec scroll rate: https://dl.dropboxusercontent.com/u/19882028/VLF/ZEVS_1st.png

It looks like i need some more gain on the lower frequencies. Will modify the circuit a bit...

73, Stefan/DK7FC


From: DK7FC
Sent: Sunday, September 28, 2014 4:28 PM
Subject: LF: ZEVS RX ant question

HI VLF,

Yesterday i tried again to receive ZEVS. I didn't know if it was on air but gave it a try. Recorded about 2 hours of the VLF spectrum received on my T antenna (i.e. E-field). I also used a source follower (J310) but added a 3 stage RC filter in front of the gate. I thought i can afford some pF against ground now with the relatively large antenna which must have about 150 pF. I used this circuit: https://dl.dropboxusercontent.com/u/19882028/VLF/ZEVS%20test%20ant.jpg

But somehow the spectrum looks not as expected. While the MSKs are still strong, there is much noise below 2 kHz and the sferics appear to be quite weak. See: https://dl.dropboxusercontent.com/u/19882028/VLF/Garden%20T%20antenna%20VLF%201.png

I remember from tests with a small active antenna for VLF, where i used 100 MOhm resistors on the gate, that charged humidity caused much noise.
Could this be the same effect here?
Should i try to use a lower input impedance of the preamp?
Maybe you remember, there were certain transistors, several decades ago, they were called bipolar transistors, NPN and PNP. Maybe i should try one of them? :-)

 Advice is apprechiated. Where are the experts?

73, Stefan/DK7FC
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