Return-Path: Received: from rly-da02.mx.aol.com (rly-da02.mail.aol.com [172.19.129.76]) by air-da03.mail.aol.com (v123.4) with ESMTP id MAILINDA031-a574a190c4e306; Sun, 24 May 2009 04:59:14 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-da02.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDA027-a574a190c4e306; Sun, 24 May 2009 04:58:56 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M89X9-0006yh-AL for rs_out_1@blacksheep.org; Sun, 24 May 2009 09:58:19 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M89X8-0006yY-Jb for rsgb_lf_group@blacksheep.org; Sun, 24 May 2009 09:58:18 +0100 Received: from mail-gx0-f170.google.com ([209.85.217.170]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M89X3-0006p0-1d for rsgb_lf_group@blacksheep.org; Sun, 24 May 2009 09:58:17 +0100 Received: by gxk18 with SMTP id 18so2415881gxk.4 for ; Sun, 24 May 2009 01:58:05 -0700 (PDT) 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=MsvdieUh7DEvKVoSMxoHzUVBCJnXeWfeE3vPiSYwiSY=; b=eI1VhTQxXrJtPSghA5xZ7dWIvWaZUD3c/Yxm6hIAtK41SI4AQxj1PyURIfWmkFiYUH V1LCERPZmiMf0Kz90PCqfmYymBOqNyS8MvRMU3ecljNGQxKG5zbW9waKvogWNYm5gmt0 QK2RhINA6c3KEwcCs1as2AAz0xyXMfE6fAbK4= 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=iETQl5fS5sI9+GOFfIaSylfVtz8HwTRe3s591XC43wW6BDJ3OwwR6u8025z0kCsvKz B1UeUS6ke7RBNCLskHIV/Qd3O5rSvUwnlLQGP3+l3aX3cw1HA4mQUMyIe2bCkffTgFZh lFwutf/gvBLFcBPJhvK03Apo7/R/u4a6FLihk= MIME-Version: 1.0 Received: by 10.151.73.9 with SMTP id a9mr11499517ybl.60.1243155484534; Sun, 24 May 2009 01:58:04 -0700 (PDT) In-Reply-To: <8CBA9F282F0E172-BD8-2E43@webmail-mf12.sysops.aol.com> References: <4A181EEC.5050600@btconnect.com> <8CBA9F282F0E172-BD8-2E43@webmail-mf12.sysops.aol.com> Date: Sun, 24 May 2009 09:58:04 +0100 Message-ID: <88d2415e0905240158l205c0700y3413766a82d07827@mail.gmail.com> From: lawrence mayhead To: rsgb_lf_group@blacksheep.org X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: First Portable Trip Content-Type: multipart/alternative; boundary=001e680f0ff80e6697046aa4b1ab 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=CLICK_BELOW, HTML_LINK_CLICK_HERE,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-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d271.1 ; domain : googlemail.com DKIM : pass X-Mailer: Unknown (No Version) --001e680f0ff80e6697046aa4b1ab Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Richard, I must commend your efforts to go portable. However there seems to me to be one major problem. That is GROUND, all antennas except loops (more later) need to work against "Ground" which is not really ground as we know it since at LF the earth is pretty transparent, varies a bit, but mainly RF penetrates many feet. Think about cave radio. So we use counterpoise/radial etc. wires, but to be any good these have to be quarter wave long! ie 125meters !!! not easy when you are portable. At home the mains feed, is probably the best radial available, since it goes to all the other houses far and near. So your problem is not so much to fly a kite or balloon but to find a few hundred yards of viable fencing/old railway etc. But Loops are different, no ground required and mebbe you could lay a horizontal loop out on the ground (its pretty transparent after all ) better still a mountain site not in East Sussex though I guess. Lots of data on LF Loops on the reflector, matching etc. Best of luck and will always listen for you 73 Laurie. 2009/5/23 > Hi Richard. > > I've used a system similar to yours with some success. Mine, now > dismantled, is detailed at > > http://www.g0mrf.com/500kAntenna.htm > > It was a 10m mast with a very small 3m top section. Power in 7.5W PEP. > 100km was no problem 24/7 with good conditions it made it to ON and PA. > With very good conditions it made it to the Scotish Islands at apx 800km but > that was rare. > > The photo shows a variometer in series with a fixed coil in series with > another fixed coil which was connected to ground at the bottom end. Despite > all these turns of wire, the 50 ohm match was only a few turns up from the > ground end. > > Hope that helps. > > David > > > > > > -----Original Message----- > From: Richard Newstead > To: rsgb_lf_group@blacksheep.org > Sent: Sat, 23 May 2009 16:06 > Subject: LF: First Portable Trip > > Not a great success. Tried a 200ft inverted L with 7m vertical section fed > against 3 radials each between 50 and 100ft long. The final 100ft was very > low - within 1 metre of the ground. > > Did not succeeded in tuning aerial up in link configuration. Tried tapping > the feeder at various points on the main coil but this reduced the Q > dramatically and the RX and TX performance were very poor. In configurations > where the RX performance was good and the Q high, there was little on no > aerial current on transmit. The only configuration that gave some antenna > current was nearly useless on receive. Connecting a radial to a metal fence > detuned things so much that I go nowhere like that. > > Heard GW0HXO's beacon at reasonable strength and GW3UEP's beacon - just. > Called CQ quite a few times. No takers. > > Band was still noisy even on relatively remote hilltop with horrible > "line-timebase" type burble drifting across band. > > Clearly more work required to get a viable system. Tips? > > 73 > > Richard > G3CWI > > > ------------------------------ > Click here to get the very > best of AOL, including news, sport, gossip, lifestyles updates and email. > --001e680f0ff80e6697046aa4b1ab Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Richard,
I must commend your efforts to go portable. However there see= ms to me to be one major problem. That is GROUND, all antennas except loops=20= (more later) need to work against "Ground" which is not really gro= und as we know it since at LF the earth is pretty transparent, varies a bit,= but mainly RF penetrates many feet. Think about cave radio. So we use count= erpoise/radial etc. wires, but to be any good these have to be quarter wave=20= long! ie 125meters !!! not easy when you are portable. At home the mains fee= d, is probably the best radial available, since it goes to all the other hou= ses far and near. So your problem is not so much to fly a kite or balloon bu= t to find a few hundred yards of viable fencing/old railway etc.
But Loops are different, no ground required and mebbe you could lay a horizo= ntal loop out on the ground (its pretty transparent after all ) better still= a mountain site not in East Sussex though I guess. Lots of data on LF Loops= on the reflector, matching etc.
Best of luck and will always listen for you
73 Laurie. =A0

2009/5/23 <g0mrf@aol.com>
Hi Richard.

I've used a system similar to yours with some success.=A0 Mine, now dism= antled, is detailed at

http://ww= w.g0mrf.com/500kAntenna.htm

It was a 10m mast with a very small 3m top section. Power in 7.5W PEP.
100km was no problem 24/7 with good conditions it made it to ON and PA.=A0 W= ith very good conditions it made it to=A0the Scotish Islands at apx 800km bu= t that was rare.

The photo shows a variometer in series with a fixed coil in series with anot= her fixed coil which was connected to ground at the bottom end.=A0 Despite a= ll these turns of wire, the 50 ohm match was only a few turns up from the gr= ound end.

Hope that helps.

David





-----Original Message-----
From: Richard Newstead <g3cwi@btconnect.com>
To: rsgb_l= f_group@blacksheep.org
Sent: Sat, 23 May 2009 16:06
Subject: LF: First Portable Trip

No= t a great success. Tried a 200ft inverted L with 7m vertical section fed aga= inst 3 radials each between 50 and 100ft long. The final 100ft was very low=20= - within 1 metre of the ground.=A0
=A0
Did not succeeded in tuning aerial up in link configuration. Tried tapping t= he feeder at various points on the main coil but this reduced the Q dramatic= ally and the RX and TX performance were very poor. In configurations where t= he RX performance was good and the Q high, there was little on no aerial cur= rent on transmit. The only configuration that gave some antenna current was=20= nearly useless on receive. Connecting a radial to a metal fence detuned thin= gs so much that I go nowhere like that.=A0
=A0
Heard GW0HXO's beacon at reasonable strength and GW3UEP's beacon - j= ust. Called CQ quite a few times. No takers.=A0
=A0
Band was still noisy even on relatively remote hilltop with horrible "l= ine-timebase" type burble drifting across band.=A0
=A0
Clearly more work required to get a viable system. Tips?=A0
=A0
73=A0
=A0
Richard=A0
G3CWI=A0
=A0

=
= Click here to get the very best of AOL, including news, sport, gossip, l= ifestyles updates and email.

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