Return-Path: Received: from mtain-mb03.r1000.mx.aol.com (mtain-mb03.r1000.mx.aol.com [172.29.96.23]) by air-dc02.mail.aol.com (v127_r1.1) with ESMTP id MAILINDC024-86a04b865391263; Thu, 25 Feb 2010 05:40:17 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mb03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 8B848380000BC; Thu, 25 Feb 2010 05:40:15 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Nkb7P-0001jC-Ji for rs_out_1@blacksheep.org; Thu, 25 Feb 2010 10:38:55 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Nkb7O-0001j3-SN for rsgb_lf_group@blacksheep.org; Thu, 25 Feb 2010 10:38:54 +0000 Received: from web28102.mail.ukl.yahoo.com ([217.146.182.122]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1Nkb7O-00030j-EV for rsgb_lf_group@blacksheep.org; Thu, 25 Feb 2010 10:38:54 +0000 Received: (qmail 9430 invoked by uid 60001); 25 Feb 2010 10:38:47 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.co.uk; s=s1024; t=1267094327; bh=17dNAWOWslaM9EigBG5bxiCq3U3wbDy6WELZKjKyVqg=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=IIQd1PXrXr/BtBvQGLutFNiTpekYUJnRBB1gKcN+fqEk778ewhAQSfGEKMGiaYsx8q6HvGi3ggRzgUEHmkfHCd9pEu5WqDBe5sze8Ffps7pM3mDMZ8QURUwbiBzQTRVGTwqMbo19GIrcvo4KcFZdcdA63kplH1K6tO+LFOmIMWs= DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.co.uk; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=WyA4t3lD8iB7WoNIBIZ3VnQ/k9RcbIo99QgHG1t5DJT9YwCIATsQibObJtWMRWv3CaeOPDJwD3xt+O3/AvjtulSQC7i3TbZ/pWopxR1k6pCO+/Ymnw3qdJ96dYYkX7fZMFMJiGtLu+nQBWXBZsMVvBr+PVEign9eP4+ijOBRyKE=; Message-ID: <818138.8525.qm@web28102.mail.ukl.yahoo.com> X-YMail-OSG: yVPGcOcVM1l4Hf.fiA7F3inJqQ0tZ.2RbvTxUcCRIwatfZtLf6VuxiJE4rBO6A2_JZ.vzovPMrZNlkRkzYzcvlJ1kDAUFkvTbiKOZpFUALIKMwoTokfyMrc3VXTxsuK1kYVngD.Ntz157z4gSxlFcoKrDM7yLd.lEiOvnyqqaH_jjIPP2V2tjPhvq6ZLAdm4OLRJoAEK05Ul8j_gOjaZl2_yu_XwWorVfE6QdWIEP3B0rjoti6SZ7OmnNdocx3IfVLaM4tKWRV0Ujr9yd8p15ws1Qb8- Received: from [81.129.13.50] by web28102.mail.ukl.yahoo.com via HTTP; Thu, 25 Feb 2010 10:38:47 GMT X-Mailer: YahooMailClassic/9.2.12 YahooMailWebService/0.8.100.260964 Date: Thu, 25 Feb 2010 10:38:47 +0000 (GMT) From: M0FMT To: rsgb_lf_group@blacksheep.org In-Reply-To: <2021F4D9DCF542B290883FF2F30AB357@lindavideo> MIME-Version: 1.0 DomainKey-Status: good (testing) Subject: Re: LF: RE: Re: VLF_8.79 kHz Content-Type: multipart/alternative; boundary="0-1926506509-1267094327=:8525" 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-d235.1 ; domain : yahoo.co.uk DKIM : pass x-aol-sid: 3039ac1d60174b86538f2eb0 X-AOL-IP: 193.82.116.20 --0-1926506509-1267094327=:8525 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Ken. Why not just stick an antenna wire into your Sound card mic socket and ins= tall 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. Us= ing SDR software you can then record the result in real time spectrum allo= wing it to be processed by others.=20 =A0 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.=20 =A0 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 gettin= g 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 these antennas becau= se my best calculations say if I use a kW the coil about 1 Henry will diss= ipate most of the power which means it be=A0getting very very hot and prob= ably fail and need over 2 km of wire. Totally impractical!=A0Some ideas ha= ve been kicked around on the is reflector and off list there may be someth= ing 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 yo= u put up some diagrams etc of your parallel capacitor and other antenna configurations and formulae. 73. Ken M0KHW=A0 =A0 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, 40= m=20 long inv-L antenna at my home QTH, and also a near-identical antenna set= up=20 in the middle of a field away from trees and buildings. The attached graph= =20 shows Rloss plotted against frequency over the range 10kHz to 600kHz for= =20 both antennas. At all frequencies, the loss resistance of the open-field= =20 antenna is much lower than the home QTH antenna, which is surrounded by=20 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 10kHz, the open=A0 field antenna has Rloss of 50R, against 380R for the= =20 home QTH antenna. Both antennas show a decreasing Rloss with frequency -= =20 this suggests dielectric losses are dominant (the antenna voltage increase= s=20 at lower frequencies for a given current) in both cases. The text books sa= y, for electrically small antennas, that dielectric losses will dominate at= low frequencies, while at high frequencies the skin effect will eventually cau= se resistance to start increasing - in the case of the open field antenna, a= =20 turn-over point might have been reached at a few hundred kHz. The 50R figure suggests that antenna efficiency might actually be higher= at=20 9kHz than people are expecting - at least in an open field site. A suitabl= e=20 loading coil would be a problem. The antenna capacitance was around 350pF= -=20 in these experiments I used a ferrite-cored coil of around 0.7H with a Q= of=20 about 150, but this had a loss resistance of about 300R. If you tolerated= =20 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= =20 the antenna would definitely be useful... Cheers, Jim Moritz 73 de M0BMU =20 --0-1926506509-1267094327=:8525 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
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.
 
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 exercis= e I can let you know when my setup is working. Now that the weather is get= ting 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 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 getting= very very hot and probably fail and need over 2 km of wire. Totally impra= ctical! Some ideas have been kicked around on the is reflector and of= f list there may be something I can try.

73 es GL petefmt

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

From: Ken <ken.h.wright@btinternet.com><= BR>Subject: LF: RE: Re: VLF_8.79 kHz
To: rsgb_lf_group@blacksheep.orgDate: 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 followi= ng this thread with interest, could you
put up some diagrams etc of you= r 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 Februar= y 2010 21:14
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: VLF_8.79 kH= z

Dear LF Group,

A couple of years ago I did some measuremen= ts of Rloss of the 10m high, 40m
long inv-L antenna at my home QTH, an= d also a near-identical antenna set up
in the middle of a field away= from trees and buildings. The attached graph
shows Rloss plotted agai= nst frequency over the range 10kHz to 600kHz for
both antennas. At all= frequencies, the loss resistance of the open-field
antenna is much lo= wer 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&= nbsp; field antenna has Rloss of 50R, against 380R for the
home QTH an= tenna. 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 st= art increasing - in the case of the open field antenna, a
turn-over po= int might have been reached at a few hundred kHz.

The 50R figure su= ggests that antenna efficiency might actually be higher at
9kHz than= people are expecting - at least in an open field site. A suitable
loa= ding 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 yo= u 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 capac= itance of
the antenna would definitely be useful...

Cheers, Jim= Moritz
73 de M0BMU


=20 --0-1926506509-1267094327=:8525--