Return-Path: X-Spam-DCC: paranoid 1290; 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=-1.9 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_40_50,HTML_MESSAGE 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 t350d2R0021331 for ; Sun, 5 Apr 2015 02:39:02 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1YeYXE-00035l-5n for rs_out_1@blacksheep.org; Sun, 05 Apr 2015 01:35:32 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1YeYXD-00035c-IX for rsgb_lf_group@blacksheep.org; Sun, 05 Apr 2015 01:35:31 +0100 Received: from omr-m07.mx.aol.com ([64.12.143.81]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.85) (envelope-from ) id 1YeYXB-0000p1-6G for rsgb_lf_group@blacksheep.org; Sun, 05 Apr 2015 01:35:30 +0100 Received: from mtaout-mbc02.mx.aol.com (mtaout-mbc02.mx.aol.com [172.26.221.142]) by omr-m07.mx.aol.com (Outbound Mail Relay) with ESMTP id C074970000094 for ; Sat, 4 Apr 2015 20:35:26 -0400 (EDT) Received: from White (ipb21bee4a.dynamic.kabel-deutschland.de [178.27.238.74]) by mtaout-mbc02.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 094673800008C for ; Sat, 4 Apr 2015 20:35:23 -0400 (EDT) Message-ID: From: "Markus Vester" To: References: <551F1D67.8050609@gmail.com> <552009D2.3070105@gmail.com> Date: Sun, 5 Apr 2015 02:35:32 +0200 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20140625; t=1428194126; bh=bHuh0Nk6Dq7IgsjgxLuuykwqfJREw/GVA9G7G3EDzng=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=BXOdubo3744In7ktDbAHFTrWg0OEUTJHSZTTjh9AUYSyUOecymOgXhgPJhHbI7wAT m5GUWqusDryStsT9r65ZgT6Q2B0KVxizUZkopG4NoGe8+Tm+ohqB9CjbcmES5E2xzz tjYm6CsTDNWddZjMH8rJKIOvhSu0kVjuxjxLE7mU= x-aol-sid: 3039ac1add8e5520834b4390 X-AOL-IP: 178.27.238.74 X-Scan-Signature: e21031ef48bbae1c5a8c64549547751e Subject: Re: LF: VLF in Canada Content-Type: multipart/alternative; boundary="----=_NextPart_000_0003_01D06F49.300BCD80" 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: 2883 Dies ist eine mehrteilige Nachricht im MIME-Format. ------=_NextPart_000_0003_01D06F49.300BCD80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Joe,=20 sounds good! At 1.25 km you're still in the reactive nearfield, where = signal transfer occurs by capacitive coupling rather than Hertzian wave = propagation. In that regime, electric field strength is governed by an = inverse cube law, falling off rather steeply at 60 dB per range decade. The SNR of your audible CW signal would probably have been on the order = of 10 dB in 50 Hz. If you went to QRSS-3 you'd gain around 20 dB, which = would get you to 2.7 km. To reach the radiation field boundary = (lambda/2pi =3D 5.77 km), you'd need another 20 dB, or 100-fold symbol = length (ie 300 s dots). The good news is that beyond that point, it gets = much easier to go further at 20 dB/decade. For the very slow modes, it would probably be better to do away with the = receiver and connect the antenna directly to a laptop soundcard. Then = you can use SpecLab's sophisticated samplerate tracking functions and = achieve ultimate frequency stability. On the transmit side, it's more important to design the antenna and coil = for voltage capability than for highest Q factor. It's relatively easy = to overcome losses by a stronger power amplifier. Maximum achievable ERP = from a small electrical antenna scales with (voltage withstanding * = antenna capacitance * effective height)^2 * frequency^4. All the best, Markus (DF6NM) From: jcraig@mun.ca=20 Sent: Sunday, April 05, 2015 12:33 AM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: VLF in Canada Dear Group, Last summer, my VLF CW signals were copied outside my back yard. Today, using a Marconi XH-100 with a SRA-8 mixer & AD9850/Arduino LO and a=20 National LF-10 preselector, the sigs could be clearly heard outside my = town with a 20 metre wire aerial strung between the car and a road sign. For = TX, the 100m wire (~15 m high) was coupled with 425 mH to a variac (2:1) = in series with a 5:1 ferrite xfmr to the keyboard amp with the volume = control=20 set to 5 (about 30 watts). This is DX record on 8.277 kHz for this station -- 1.25 km! I wonder how = far away it could be copied with QRSS? Any TA attempt will have to wait = until a higher Q tuning coil appears. The DC resistance of the current = one is almost 1k and I think it has much series capacitance. It gets warm=20 and emits an stench of ozone when in use. 73 Joe VO1NA ------=_NextPart_000_0003_01D06F49.300BCD80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Joe,
 
sounds good! At 1.25=20 km you're still in the reactive nearfield, where signal transfer = occurs=20 by capacitive coupling rather than Hertzian wave propagation. In = that=20 regime, electric field strength is governed by an inverse cube law, = falling=20 off rather steeply at 60 dB per range decade.
 
The SNR of your audible CW signal = would=20 probably have been on the order of 10 dB in 50 Hz. If you went = to QRSS-3 you'd gain around 20 dB, which would get you to 2.7 = km.=20 To reach the radiation field boundary (lambda/2pi =3D 5.77 km), = you'd need=20 another 20 dB, or 100-fold symbol length (ie 300 s = dots). The=20 good news is that beyond that point, it gets much easier to go further = at 20=20 dB/decade.
 
For the very slow modes, it would = probably be=20 better to do away with the receiver and connect the = antenna directly to a=20 laptop soundcard. Then you can use SpecLab's sophisticated = samplerate=20 tracking functions and achieve ultimate frequency = stability.
 
On the transmit side, it's = more important=20 to design the antenna and coil for voltage capability than for highest Q = factor.=20 It's relatively easy to overcome losses by a stronger power = amplifier.=20 Maximum achievable ERP from a small electrical antenna scales = with (voltage=20 withstanding * antenna capacitance * effective height)^2 *=20 frequency^4.
 
All the best,
Markus (DF6NM)

From: jcraig@mun.ca
Sent: Sunday, April 05, 2015 12:33 AM
Subject: LF: VLF in Canada

Dear Group,

Last summer, my VLF CW = signals=20 were copied outside my back yard. Today,
using a Marconi XH-100 with = a SRA-8=20 mixer & AD9850/Arduino LO and a
National LF-10 preselector, the = sigs=20 could be clearly heard outside my town
with a 20 metre wire aerial = strung=20 between the car and a road sign.  For
TX, the 100m wire (~15 m = high)=20 was coupled with 425 mH to a variac (2:1) in
series with a 5:1 = ferrite xfmr=20 to the keyboard amp with the volume control
set to 5 (about 30=20 watts).

This is DX record on 8.277 kHz for this station -- 1.25 = km! I=20 wonder how
far away it could be copied with QRSS?  Any TA = attempt will=20 have to wait
until a higher Q tuning coil appears.  The DC = resistance=20 of the current one
is almost 1k and I think it has much series = capacitance.=20 It gets warm
and emits an stench of ozone when in = use.

73
Joe=20 VO1NA

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