Return-Path: Received: (qmail 25890 invoked from network); 18 Jan 2001 11:39:32 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by extortion.plus.net with SMTP; 18 Jan 2001 11:39:32 -0000 Received: (qmail 25966 invoked from network); 18 Jan 2001 11:42:14 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 18 Jan 2001 11:42:14 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14JDIe-0000Sq-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 18 Jan 2001 11:32:16 +0000 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14JDId-0000Sl-00 for rsgb_lf_group@blacksheep.org; Thu, 18 Jan 2001 11:32:15 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id LAA18259; Thu, 18 Jan 2001 11:33:18 GMT Received: (qmail 25399 invoked from network); 18 Jan 2001 12:25:48 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 18 Jan 2001 12:25:48 -0000 Received: by gauntlet.mail.dera.gov.uk; id MAA08709; Thu, 18 Jan 2001 12:17:38 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma008603; Thu, 18 Jan 01 12:17:19 GMT Received: from FRN-MAIL-3.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Thu, 18 Jan 2001 11:34:43 +0000 Received: by frn-mail-3.dera.gov.uk with Internet Mail Service (5.5.2650.21) id ; Thu, 18 Jan 2001 11:31:46 -0000 Message-ID: <65AECDF1F89AD411900400508BFC869F0D7529@pdw-mail-1.dera.gov.uk> From: "Talbot Andrew" To: "LF Group \(E-mail\)" Subject: LF: Dipole antenna at LF Date: Thu, 18 Jan 2001 11:31:50 -0000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/html; charset=windows-1252 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Content-transfer-encoding: 8bit

A new subject now .....

Someone must have already tried this, but how effective would a (say) 100m long dipole laid down a chalk hill be ?

Isn't limestone also the same material as chalk, Are there any CREG members reading this who know about conductivity of rocks?

Chalk is a very poor conductor, even when wet. A 4m earthing rod driven into the top of Portsdown Hill on the South coast of the UK in an attempt to make an RF ground measured 120 ohms to mains Earth - attempt abandoned in favour of a dipole !

There are plenty of chalk hills of this sort of height, and the amount of wire needed - 500m perhaps - means the radiation resistance will rise to an acceptable figure to reduce copper loss.

Andy G4JNT





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