Return-Path: Received: (qmail 11787 invoked from network); 21 Jun 1999 16:13:37 +0100 Received: from magnet.plus.net.uk (HELO magnet.force9.net) (195.166.128.26) by guiness.force9.net with SMTP; 21 Jun 1999 16:13:37 +0100 Received: (qmail 25394 invoked from network); 21 Jun 1999 15:13:29 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnet.plus.net.uk with SMTP; 21 Jun 1999 15:13:29 -0000 X-Priority: 3 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 10w5X7-0005Zz-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 21 Jun 1999 15:58:49 +0100 X-MSMail-Priority: Normal Received: from relay1.mail.uk.psi.net ([154.32.105.6]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 10w5X6-0005Zu-00 for rsgb_lf_group@blacksheep.org; Mon, 21 Jun 1999 15:58:48 +0100 Received: from mail.itexgsy.com ([195.153.167.5] helo=itxint02.itexjsy.com) by relay1.mail.uk.psi.net with esmtp (Exim 2.12 #2) id 10w5Wr-00076v-00 for rsgb_lf_group@blacksheep.org; Mon, 21 Jun 1999 15:58:33 +0100 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: by ITXINT02 with Internet Mail Service (5.5.2448.0) id ; Mon, 21 Jun 1999 15:57:54 +0100 Message-ID: From: "Phil Daniells" To: rsgb_lf_group@blacksheep.org Subject: LF: RE: Antennas Date: Mon, 21 Jun 1999 15:57:30 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2448.0) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Sender: > -----Original Message----- > From: Mike Dennison [SMTP:mike.dennison@rsgb.org.uk] > Sent: Monday, June 21, 1999 2:27 PM > To: rsgb_lf_group@blacksheep.org > Subject: LF: Antennas > > I have done very many antenna experiments over the past 2-3 > years to get a better signal at 73 and 136kHz from a small garden. > > I have experimented with inverted-L Marconis. These have mainly > sloped down from the top of the vertical section and I have on two > occasions increased the height of the far end with improved results. > It seems that at LF you cannot get away with drooping the far end > of an inverted-L like you can at HF. This is presumably because > the current distribution is approximately linear for a short Marconi > and sinusoidal for something a quarter-wave or more. > [CBQ>] You don't get away with it on HF either. My experience on 160 is that inverted-Ls invariably work better with horizontal tops rather than sloping ones, possibly losses associated with the high voltage end of the aerial are lower and the radiation resistance is higher. There was a QST article dealing with this some while back (I'm sorry but I don't recall the issue). The conclusion was that sloping the far end below ~50% of the height of the vertical section was counterproductive. > Also, if I run three top wires in parallel, should I join them at > the far end? [CBQ>] I recall another QST article (but not the date of issue) that dealt with broad-banding an 80 metre dipole using a multi-wire top. The advice was not to connect the parallel wires together at the far end, though I can't remember why. Cheers, Phil, GJ4CBQ.