Return-Path: Received: from mtain-dc03.r1000.mx.aol.com (mtain-dc03.r1000.mx.aol.com [172.29.64.131]) by air-dc05.mail.aol.com (v129.4) with ESMTP id MAILINDC053-86514d72920613c; Sat, 05 Mar 2011 14:41:58 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc03.r1000.mx.aol.com (Internet Inbound) with ESMTP id E077938000090; Sat, 5 Mar 2011 14:41:56 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PvxLV-0007Hh-51 for rs_out_1@blacksheep.org; Sat, 05 Mar 2011 19:40:57 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PvxLT-0007HY-LY for rsgb_lf_group@blacksheep.org; Sat, 05 Mar 2011 19:40:55 +0000 Received: from out1.ip02ir2.opaltelecom.net ([62.24.128.238]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PvxLR-0007vN-GB for rsgb_lf_group@blacksheep.org; Sat, 05 Mar 2011 19:40:55 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AsADABMhck0CZMwO/2dsb2JhbAAMC6F5mXepKoViBJAN X-IronPort-AV: E=Sophos;i="4.62,269,1297036800"; d="scan'208,217";a="357840333" Received: from unknown (HELO [192.168.2.2]) ([2.100.204.14]) by out1.ip02ir2.opaltelecom.net with ESMTP; 05 Mar 2011 19:40:45 +0000 Message-ID: <4D7291BD.8080301@talktalk.net> Date: Sat, 05 Mar 2011 19:40:45 +0000 From: "qrss@talktalk.net" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <4D72471D.30904@talktalk.net> <4D72695E.3090100@talktalk.net> In-Reply-To: X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: Sub 9kHz antenna tests. Content-Type: multipart/alternative; boundary="------------000208000205070409060701" 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-sid: 3039ac1d40834d72920439aa X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --------------000208000205070409060701 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi Gary Yes I see Jim 'tunes' his loop after the coax feed or is it HF filtering. My Loop is 800mm sq 50 turns and 3.6mH according to rjeloop. I am using SpecLab and PC 73 Eddie . On 05/03/2011 18:52, Gary - G4WGT wrote: > 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. >> >> >> >> > > --------------000208000205070409060701 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Gary

Yes I see Jim 'tunes' his loop after the coax feed or is it HF filtering.

My Loop is 800mm sq 50 turns and 3.6mH according to rjeloop.

I am using SpecLab and PC

73 Eddie
.
On 05/03/2011 18:52, Gary - G4WGT wrote:
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 <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 <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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