Return-Path: Received: from mtain-dg09.r1000.mx.aol.com (mtain-dg09.r1000.mx.aol.com [172.29.65.17]) by air-md06.mail.aol.com (v127_r1.1) with ESMTP id MAILINMD063-8b8a4b865f16364; Thu, 25 Feb 2010 06:29:26 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dg09.r1000.mx.aol.com (Internet Inbound) with ESMTP id 07B4238000106; Thu, 25 Feb 2010 06:29:22 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NkbtF-0002K6-R2 for rs_out_1@blacksheep.org; Thu, 25 Feb 2010 11:28:21 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NkbtF-0002Jx-5o for rsgb_lf_group@blacksheep.org; Thu, 25 Feb 2010 11:28:21 +0000 Received: from mail-bw0-f215.google.com ([209.85.218.215]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NkbtD-0003e0-Iz for rsgb_lf_group@blacksheep.org; Thu, 25 Feb 2010 11:28:21 +0000 Received: by bwz7 with SMTP id 7so4443036bwz.4 for ; Thu, 25 Feb 2010 03:28:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=X8nvZXKh8twmfBwUwQYf58aGUduqfuKPm6tQL8z/eps=; b=ijAqy/tIXoYAqfafd1yJLVks+7NyJQg1LYAXxEJWNqEEme3zOFAJQwg5KE94uaFFNr ZrX6f+w9SqXyB5FTL/xRnuJAfa0xYzSq8r+7QQdLbmiAyppcL4j734cGum9QX78ywRw3 jKu4lODOzmjWWAoEYppj8cakq22mfTDxTk5h8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=HCqQtrvqSpRIV/B83v8hx90pYAfngxr2Vlaowe5t6P+t8ZmRQ3c7wXYYw7ufGUTTUm I1nhHzK6edCZI56H+2ElJCfQBKJMR7YFfzxepYGrf8B8OCOjbREpe+Y+2DdsDXDff32U lT2+d+E/psyohv48dA0siYqTJWZKSiNALFAeE= MIME-Version: 1.0 Received: by 10.204.32.74 with SMTP id b10mr664694bkd.38.1267097292799; Thu, 25 Feb 2010 03:28:12 -0800 (PST) In-Reply-To: <72058C74D1E84593AE608BA4ED0E2297@IBM7FFA209F07C> References: <818138.8525.qm@web28102.mail.ukl.yahoo.com> <72058C74D1E84593AE608BA4ED0E2297@IBM7FFA209F07C> Date: Thu, 25 Feb 2010 11:28:12 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,HTML_TAG_EXIST_TBODY=0.126 Subject: Re: LF: RE: Re: VLF_8.79 kHz Content-Type: multipart/alternative; boundary=000325555bf20881c704806b14d4 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=HTML_MESSAGE, HTML_TAG_EXISTS_TBODY 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-d305.1 ; domain : googlemail.com DKIM : pass x-aol-sid: 3039ac1d41114b865f127cc8 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --000325555bf20881c704806b14d4 Content-Type: text/plain; charset=ISO-8859-1 I dunno.... Some 99p headphone 'dongles' from Ebay deserve that sort of treatment. Andy www.g4jnt.com On 25 February 2010 11:16, Chris wrote: > You should NEVER 'stick an antenna wire into your sound card'. > Chris, G4AYT, Whitstable, Kent. > > ----- Original Message ----- > *From:* M0FMT > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Thursday, February 25, 2010 10:38 AM > *Subject:* Re: LF: RE: Re: VLF_8.79 kHz > > Ken. > Why not just stick an antenna wire into your Sound card mic socket and > install either Argo Spectran or Spec lab FFT application. You then have DC > to 48kc/s VLF coverage with the ability to detect very very weak signals. > Using SDR software you can then record the result in real time spectrum > allowing it to be processed by others. > > This type of set up is used by many people to copy SAQ on 17.2kc/s. > > It is the method we are using here for some simple tests on 7.8125kc/s and > or 9.765625kc/s depending upon xtal used. > > You are about 11km from this location if you are keen on this exercise I > can let you know when my setup is working. Now that the weather is getting > better I will be able to get out working on the antenna. > > Two arrangements will be tried a vertical loop up abt 12/13m and an earth > electrode method. I have no real idea of how to load these antennas because > my best calculations say if I use a kW the coil about 1 Henry will dissipate > most of the power which means it be getting very very hot and probably fail > and need over 2 km of wire. Totally impractical! Some ideas have been kicked > around on the is reflector and off list there may be something I can try. > > 73 es GL petefmt > > --- On *Thu, 25/2/10, Ken * wrote: > > > From: Ken > Subject: LF: RE: Re: VLF_8.79 kHz > To: rsgb_lf_group@blacksheep.org > Date: Thursday, 25 February, 2010, 10:05 > > Hi Jim. > I think I could knock up a quick 9kHz RX here in Luton over the weekend if > that would help. I have been following this thread with interest, could you > put up some diagrams etc of your parallel capacitor and other antenna > configurations and formulae. > > 73. > Ken > M0KHW IO91TV > > -----Original Message----- > From: owner-rsgb_lf_group@blacksheep.org > [mailto:owner-rsgb_lf_group@blacksheep.org] > On Behalf Of James Moritz > Sent: 24 February 2010 21:14 > To: rsgb_lf_group@blacksheep.org > Subject: LF: Re: VLF_8.79 kHz > > Dear LF Group, > > A couple of years ago I did some measurements of Rloss of the 10m high, 40m > > long inv-L antenna at my home QTH, and also a near-identical antenna set up > > in the middle of a field away from trees and buildings. The attached graph > shows Rloss plotted against frequency over the range 10kHz to 600kHz for > both antennas. At all frequencies, the loss resistance of the open-field > antenna is much lower than the home QTH antenna, which is surrounded by > numerous small trees. The ground in both cases was 4 x 1m ground rods, > close > > to the feed point of the antenna. The actual ground around both antennas > was > > very similar - a waterlogged clay soil. > > At 10kHz, the open field antenna has Rloss of 50R, against 380R for the > home QTH antenna. Both antennas show a decreasing Rloss with frequency - > this suggests dielectric losses are dominant (the antenna voltage increases > > at lower frequencies for a given current) in both cases. The text books > say, > > for electrically small antennas, that dielectric losses will dominate at > low > > frequencies, while at high frequencies the skin effect will eventually > cause > > resistance to start increasing - in the case of the open field antenna, a > turn-over point might have been reached at a few hundred kHz. > > The 50R figure suggests that antenna efficiency might actually be higher at > > 9kHz than people are expecting - at least in an open field site. A suitable > > loading coil would be a problem. The antenna capacitance was around 350pF - > > in these experiments I used a ferrite-cored coil of around 0.7H with a Q of > > about 150, but this had a loss resistance of about 300R. If you tolerated > loosing half the TX power in the loading coil, a similar inductance with a > Q > > of around 1000 would be needed. Increasing the top-loading capacitance of > the antenna would definitely be useful... > > Cheers, Jim Moritz > 73 de M0BMU > > > > --000325555bf20881c704806b14d4 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
I dunno....
Some 99p=A0headphone =A0'dongles' from Ebay=A0deserve that so= rt of=A0treatment.
=A0
On 25 February 2010 11:16, Chris <c.ashby435@btinternet= .com> wrote:
You should NEVER 'stick an antenn= a wire into your sound card'.
Chris, G4AYT, Whitstable, Kent.
----- Original Message -----
From: M0FMT
Sent: Thursday, February 25, 2010= 10:38 AM
Subject: Re: LF: RE: Re: VLF_8.79= kHz

Ken.
Why not just stick an antenna wire into your Sound card mic socket an= d install either Argo Spectran or Spec lab FFT application.= You then have DC to 48kc/s VLF coverage with the ability to detect very= very weak signals. Using SDR software you can then record the result in= real time spectrum allowing it to be processed by others.

This type of set up is used by many people to copy SAQ on 17.2kc/= s.
=A0
It is the method we are using here for some simple tests on 7.8125kc/= s and or 9.765625kc/s depending upon xtal used.
=A0
You are about 11km from this location if you are keen on this exercis= e I can let you know when my setup is working. Now that the weather is get= ting better I=A0will be able to get out working on the antenna.
=A0
Two arrangements will be tried a vertical loop up abt 12= /13m and an earth electrode method. I have no real idea of how to load the= se antennas because my best calculations say if I use a kW the coil about= 1 Henry will dissipate most of the power which means it be=A0getting very= very hot and probably fail and need over 2 km of wire. Totally impractica= l!=A0Some ideas have been kicked around on the is reflector and off list= there may be something I can try.

73 es GL petefmt

--- On Thu, 25/2/10, Ken= <k= en.h.wright@btinternet.com> wrote:

From: Ken <ken.h.wright@btinternet.com>
Su= bject: LF: RE: Re: VLF_8.79 kHz
To: rsgb= _lf_group@blacksheep.org
Date: Thursday, 25 February, 2010, 10:05
Hi Jim.
I think I could knock up a quick 9kHz RX here in Luton ove= r the weekend if
that would help. I have been following this thread wit= h interest, could you
put up some diagrams etc of your parallel capacit= or and other antenna
configurations and formulae.

73.
Ken
M0KHW=A0 =A0 IO91TV
<= br>-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blackshe= ep.org] On Behalf Of James Moritz
Sent: 24 February 2010 21:14
T= o: rsgb_lf_group@blacksheep.org
Subject: LF: Re: VLF_8.79 kHz

Dear LF Group,

A couple of yea= rs ago I did some measurements of Rloss of the 10m high, 40m
long inv-= L antenna at my home QTH, and also a near-identical antenna set up
in= the middle of a field away from trees and buildings. The attached graph=
shows Rloss plotted against frequency over the range 10kHz to 600kHz for=
both antennas. At all frequencies, the loss resistance of the open-fi= eld
antenna is much lower than the home QTH antenna, which is surround= ed by
numerous small trees. The ground in both cases was 4 x 1m ground rods, clo= se

to the feed point of the antenna. The actual ground around both= antennas was

very similar - a waterlogged clay soil.

At 10k= Hz, the open=A0 field antenna has Rloss of 50R, against 380R for the
home QTH antenna. Both antennas show a decreasing Rloss with frequency -=
this suggests dielectric losses are dominant (the antenna voltage inc= reases
at lower frequencies for a given current) in both cases. The te= xt books say,

for electrically small antennas, that dielectric losses will dominate= at low

frequencies, while at high frequencies the skin effect will= eventually cause

resistance to start increasing - in the case of= the open field antenna, a
turn-over point might have been reached at a few hundred kHz.

The= 50R figure suggests that antenna efficiency might actually be higher at=
9kHz than people are expecting - at least in an open field site. A su= itable
loading coil would be a problem. The antenna capacitance was around 350pF= -
in these experiments I used a ferrite-cored coil of around 0.7H wit= h a Q of
about 150, but this had a loss resistance of about 300R. If= you tolerated
loosing half the TX power in the loading coil, a similar inductance with= a Q

of around 1000 would be needed. Increasing the top-loading cap= acitance of
the antenna would definitely be useful...

Cheers,= Jim Moritz
73 de M0BMU




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