Return-Path: Received: from mtain-dh06.r1000.mx.aol.com (mtain-dh06.r1000.mx.aol.com [172.29.65.26]) by air-ma09.mail.aol.com (v129.4) with ESMTP id MAILINMA091-b5344d7286c99; Sat, 05 Mar 2011 13:54:01 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh06.r1000.mx.aol.com (Internet Inbound) with ESMTP id EF8FB380000B0; Sat, 5 Mar 2011 13:53:59 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Pvwau-0006rO-MU for rs_out_1@blacksheep.org; Sat, 05 Mar 2011 18:52:48 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Pvwat-0006rF-Om for rsgb_lf_group@blacksheep.org; Sat, 05 Mar 2011 18:52:47 +0000 Received: from mail-gw0-f42.google.com ([74.125.83.42]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Pvwar-00073L-Lo for rsgb_lf_group@blacksheep.org; Sat, 05 Mar 2011 18:52:47 +0000 Received: by gwj23 with SMTP id 23so1331287gwj.1 for ; Sat, 05 Mar 2011 10:52:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; bh=XfDReckzYw9iRYwzmcUp11QJOkclLASctydz8a/6Pjc=; b=CEbNYfRjrgHXQmfM+0uWhjwB4kXeGXy//ya0j7e6TQdePna4NVKMPrfgDPHJrXZzyS RGClatZrrICZz4gTPQ9IYueVI0j79tRBKlpaKxPzffUyPbKe6scvh9dXXbEj6LrBPIkR XaI8IfyFrte4lCPfr0nfr7XJ8/HpqN3EtIBaQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=w/dA3nK1orff2wG0aODNDlB4m5CBZl2CPu7no59BYrpn7XcW/6xD1kooUGR01M0mWq RUzvVPY5FPc2CCHXcb1FjrTF9yEEAHRfzUwMzfx/D2lf8XhueLKh0P+/IabgnqZc/qnW /BCe4seVVZhfeo5qIMk275L38xER2FhZudyMY= MIME-Version: 1.0 Received: by 10.100.86.1 with SMTP id j1mr487887anb.170.1299351159096; Sat, 05 Mar 2011 10:52:39 -0800 (PST) Received: by 10.101.95.2 with HTTP; Sat, 5 Mar 2011 10:52:39 -0800 (PST) In-Reply-To: <4D72695E.3090100@talktalk.net> References: <4D72471D.30904@talktalk.net> <4D72695E.3090100@talktalk.net> Date: Sat, 5 Mar 2011 18:52:39 +0000 X-Google-Sender-Auth: 5eBf3cCe7vabInt-u-5WFQGt1DU Message-ID: From: Gary - G4WGT To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Sub 9kHz antenna tests. Content-Type: multipart/alternative; boundary=0016368e21e946c594049dc0c4f3 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.63 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-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m241.1 ; domain : gmail.com DKIM : fail x-aol-sid: 3039ac1d411a4d7286c73a39 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --0016368e21e946c594049dc0c4f3 Content-Type: text/plain; charset=ISO-8859-1 Hi Eddie, Firstly, I have not detected any signals on any of the three VLF antennas during the test period. I haven't tried my loops without a pre-amp or resonated them but I note that Jim's (M0BMU) loop is smaller than mine at 800mm x 800mm & only 30 turns (2.85mH) were mine is 1100mm x 1100mm, 46 turns & about 4mH. Jim,s pre-amp also has a tuning capacitor (fixed value) which I removed. The strange thing is that most successful loop systems seem to be 800x800 but all use a pre-amp. Well, the results of the tests show that the noise level varies quite a lot. Using a sound card & SpecLab the noise levels are as follows, the ferrite loopstick is -140 dB, the Mini-Whip is -150 dB & the large loop is -120 dB. This surprised me as I believed the loops would be quieter. The best visibility & strength of the Alpha's was using the Mini-Whip. The Mini-Whip may be the best choice for me being omni-directional & I have never seen all four of the Alpha pulses on one RSDN before using this modified Mini-Whip. At the moment (1840utc) RSDN 1 & 2 I am seeing 3 signals & RSDN3 seeing 4 signals. So, a worth while test result for me but disappointed not to receive any amateur signals. BTW, are you using SpecLab on a PC or receiving on a real receiver ?? 73, Gary - G4WGT. On 5 March 2011 16:48, qrss@talktalk.net wrote: > Hi Gary > > Thanks for the reply, first thing, for "10dB hump at 8.9kHz" read 20dB. > Direct coupling of coax to the feed was killing the Q, I have added a 4 turn > coupling loop. The flatness was only really noted once it was outside. > > I can see the need for an amplifier on a broad band loop as with the > E-Probe which is non resonant and at a few inches long hasn't got a lot > going for it but not for a resonant loop which untuned produces 10dB of > noise and resonant 30dB I am dubious still. > > Maybe M0BMU will have a comment :-) please. > > 73 Eddie G3ZJO > > > On 05/03/2011 15:21, Gary - G4WGT wrote: > > Hi Eddie, > > Yes, you will need a pre-amp, don' forget that the E-Probe has a pre-amp. > I advise you to build the M0BMU VLF pre-amp with 7 to 10 kHz band-pass > filter, circuit attached. > > 73, Gary - G4WGT. > > > On 5 March 2011 14:22, qrss@talktalk.net wrote: > >> Hi Gary >> >> I am testing a very similar loop to your 1.1m square, mine is 800mm sq. >> and uses Litz wire. Results at the same hight as my E-Probe are >> disappointing as yet. >> >> I have no pre amp on it, and am wondering whether it would be advantageous >> as when tuned to 8.9kHz the noise level rises by 10dB. I suppose I shall end >> up building an amp to try but I would welcome any thoughts from the group. >> >> 73 Eddie G3ZJO >> >> >> On 05/03/2011 12:35, Gary - G4WGT wrote: >> >>> Hi All, >>> >>> Whilst monitoring 9090kHz & 8970kHz using SpecLab at 423uHz, I am testing >>> 3 different VLF Rx antenna types :- >>> >>> 1 - An 84mH shielded ferrite loopstick (10mm x 200mm), 1 metre above >>> ground >>> 2 - A modified PA0RDT Mini-Whip, 8 metres above ground >>> 3 - A 1.1 metre square loop with 46 turns of 1mm insulated wire, 1 metre >>> above ground >>> >>> Both of the loops using M0BMU VLF pre-amp. >>> >>> I have had No. 1 connected since 2000utc last night until 1030utc this >>> morning, no signals detected on the SpecLab display. I have connected No. 2 >>> at 1030utc & notice a fall in noise level of about 10dB & a greater >>> visibility of the Alpha signals. Later today I will connect the large loop & >>> report my findings. >>> >>> 73, >>> >>> Gary - G4WGT - IO83qo. >>> >> >> >> > > --0016368e21e946c594049dc0c4f3 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Eddie,

Firstly, I have not detected any signals on= any of the three VLF antennas during the test period.

<= div>I haven't tried my loops without a pre-amp or resonated them but= I note that Jim's (M0BMU) loop is smaller than mine at 800mm x 800mm= & only 30 turns (2.85mH) were mine is 1100mm x 1100mm, 46 turns &= about 4mH. Jim,s pre-amp also has a tuning capacitor (fixed value) which= I removed. The strange thing is that most successful loop systems seem to= be 800x800 but all use a pre-amp.

Well, the results of the tests show that the noise lev= el varies quite a lot. Using a sound card & SpecLab the noise levels= are as follows, the ferrite loopstick is -140 dB, the Mini-Whip is -150= dB & the large loop is -120 dB. This surprised me as I believed the= loops would be quieter. The best visibility & strength of the Alpha&#= 39;s was using the Mini-Whip. The Mini-Whip may be the best choice for me= being omni-directional & I have never seen all four of the Alpha puls= es on one RSDN before using this modified Mini-Whip. At the moment (1840ut= c) RSDN 1 & 2 =A0I am seeing 3 signals & RSDN3 seeing 4 signals.

So, a worth while test result for me but disappointed= not to receive any amateur signals.

BTW, are you= using SpecLab on a PC or receiving on a real receiver ??

73, Gary - G4WGT.



On 5 March 2011 16:48, qrss@= talktalk.net <qrss@talktalk.net> wrote:
=20 =20 =20
Hi Gary

Thanks for the reply, first thing, for "10dB hump at 8.9kHz"= read 20dB. Direct coupling of coax to the feed was killing the Q, I have added a 4 turn coupling loop. The flatness was only really noted once it was outside.

I can see the need for an amplifier on a broad band loop as with the E-Probe which is non resonant and at a few inches long hasn't got= a lot going for it but not for a resonant loop which untuned produces 10dB of noise and resonant 30dB I am dubious still.

Maybe M0BMU will have a comment :-) please.

73 Eddie G3ZJO


On 05/03/2011 15:21, Gary - G4WGT wrote:
Hi Eddie,

Yes, you will need a pre-amp, don' forget that the E-Probe has a pre-amp. I advise you to build the M0BMU VLF pre-amp with 7 to 10 kHz band-pass filter, circuit attached.

73, Gary - G4WGT.


On 5 March 2011 14:22, qrss@talktalk.net <qrss@talktalk.net> wrote:
Hi Gary

I am testing a very similar loop to your 1.1m square, mine is 800mm sq. and uses Litz wire. Results at the same hight as my E-Probe are disappointing as yet.

I have no pre amp on it, and am wondering whether it would be advantageous as when tuned to 8.9kHz the noise level rises by 10dB. I suppose I shall end up building an amp to try but I would welcome any thoughts from the group.

73 Eddie G3ZJO


On 05/03/2011 12:35, Gary - G4WGT wrote:
Hi All,

Whilst monitoring 9090kHz & 8970kHz using SpecLab at 423uHz, I am testing 3 different VLF Rx antenna types :-

1 - An 84mH shielded ferrite loopstick (10mm x 200mm), 1 metre above ground
2 - A modified PA0RDT Mini-Whip, 8 metres above ground 3 - A 1.1 metre square loop with 46 turns of 1mm insulated wire, 1 metre above ground

Both of the loops using M0BMU VLF pre-amp.

I have had No. 1 connected since 2000utc last night until 1030utc this morning, no signals detected on the SpecLab display. I have connected No. 2 at 1030utc & notice a fall in noise level of about 10dB & a greater visibility of the Alpha signals. Later today I will connect the large loop & report my findings.

73,

Gary - G4WGT - IO83qo.





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