Envelope-to: dave@picks.force9.co.uk Delivery-date: Sun, 05 Feb 2006 10:44:56 +0000 Received: by ptb-mxcore01.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1F5hO3-0007D0-He for dave@picks.force9.co.uk; Sun, 05 Feb 2006 10:44:56 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (PlusNet MXCore v2.00) id 1F5hO3-0007BX-Ah for dave@picks.force9.co.uk; Sun, 05 Feb 2006 10:44:55 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1F5hNl-0001k0-Ci for rs_out_1@blacksheep.org; Sun, 05 Feb 2006 10:44:37 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1F5hNk-0001jr-VH for rsgb_lf_group@blacksheep.org; Sun, 05 Feb 2006 10:44:36 +0000 Received: from [62.24.128.121] (helo=smtp.talktalk.net) by relay1.thorcom.net with esmtp (Exim 4.51) id 1F5iio-0007ek-AL for rsgb_lf_group@blacksheep.org; Sun, 05 Feb 2006 12:10:42 +0000 Received: from unknown (HELO [84.13.28.139]) (84.13.28.139) by smtp.talktalk.net with ESMTP; 05 Feb 2006 10:43:59 +0000 X-BrightmailFiltered: true X-Brightmail-Tracker: AAAAAA== Received: from 127.0.0.1 (AVG SMTP 7.1.375 [267.15.0/249]); Sun, 05 Feb 2006 10:44:02 +0000 Message-ID: <007701c62a41$1414dbf0$8b1c0d54@traceydlqceh0p> From: "Tracey Gardner" To: rsgb_lf_group@blacksheep.org References: <007001c62a34$97e808b0$2101a8c0@AUG2004> Date: Sun, 5 Feb 2006 10:44:02 -0000 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Mime-Version: 1.0 Subject: LF: Active_antennas Content-Type: multipart/mixed; boundary="------------070908000106010008000305" 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-PN-SpamFiltered: by PlusNet MXCore (v2.00) This is a multi-part message in MIME format. --------------070908000106010008000305 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: 8bit

The theory behind the "height gain" observed using small LF active antennas at different heights has to do with compression of the near-earth LF potential gradient caused by the grounded "mast" holding the antenna.

The essential bit is that there is a grounded connection between the antenna and receiver, which may be just the outer of the co-ax cable.

It would be an interesting experiment to repeat the "height gain" experiment without any connection to ground.

This could be done by building an active antenna with a little transmitter to re-radiate the received LF signal (on 2.4 GHz?) and poking it up using a fibreglass mast.

If the theory is right then there wouldn't be any height gain.

Sticking to the KISS principle, how about hauling say, a battery powered SPM-3 selective level meter up a fibreglass mast and observing the signal strength at various heights through a pair of binoculars? :-)

Tracey

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