Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dd06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 12F4D380009DC; Tue, 30 Aug 2011 11:18:05 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QyQ3s-0007vr-IO for rs_out_1@blacksheep.org; Tue, 30 Aug 2011 16:17:12 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QyQ3s-0007vi-6T for rsgb_lf_group@blacksheep.org; Tue, 30 Aug 2011 16:17:12 +0100 Received: from moutng.kundenserver.de ([212.227.17.9]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QyQ3q-0007mb-RS for rsgb_lf_group@blacksheep.org; Tue, 30 Aug 2011 16:17:12 +0100 Received: from [192.168.2.102] (p548D5769.dip.t-dialin.net [84.141.87.105]) by mrelayeu.kundenserver.de (node=mrbap3) with ESMTP (Nemesis) id 0M1GfI-1RDbQn0YgK-00tMjN; Tue, 30 Aug 2011 17:17:05 +0200 Message-ID: <4E5CFEEF.6050803@legal-medicine.de> Date: Tue, 30 Aug 2011 17:17:03 +0200 From: pws User-Agent: Mozilla/5.0 (X11; U; Linux i686; de; rv:1.9.2.18) Gecko/20110616 SUSE/3.1.11 Thunderbird/3.1.11 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <16BC8B3CA8672445BC2A29B4C14A26D4379ED2AAB4@exlnmb01.eur.nsroot.net> <4DF9EFD1.5010208@iup.uni-heidelberg.de> <1313780109.51443.YahooMailNeo@web111907.mail.gq1.yahoo.com> <9CD1E11E8BC9402CB4AECECAC4088443@JimPC> <1314394178.5030.YahooMailNeo@web111905.mail.gq1.yahoo.com> <1314641183.5605.YahooMailNeo@web111910.mail.gq1.yahoo.com> <4E5CBC9A.5020900@iup.uni-heidelberg.de> <1314705226.37125.YahooMailNeo@web111901.mail.gq1.yahoo.com> <4E5CF192.3040905@legal-medicine.de> <1314715132.88047.YahooMailNeo@web111917.mail.gq1.yahoo.com> In-Reply-To: <1314715132.88047.YahooMailNeo@web111917.mail.gq1.yahoo.com> X-Provags-ID: V02:K0:zDQaun+LGHAR2OVGv+07kaSIXj1KE8sKr21Gz7b5Yp1 VV1ayF3N+nmTeJ6VJY+FrKnwiuPTBLntXsbhd3e+u4I9HM7fNr VJ6NV6LeegRHc5Y5ea/i2yZfvLnCeQIPT6b9Qx1xrB3+/p1DAm BO98APBJzZlQleLM2msrqQUhTCiRDA8NYOhmyeoKI8Mgs79E8O O4v/QmW0zCJQ8cNVmRtnI7R3EC+RL4Ckw+n+2p0AjNom2RdV8p kiI0Qxeen4DH8W9+fBsRoLQcbZIlPrF+TypHBPp840AjyCXnOI gY8XdXa2GZIBVZ8xkXGZHFFtLN1qzsgh0JIVZ0uGi/sikCcHHV 9yr4GcJ9+xv9Rg1xj1MAXExB1DI7Dq+9ENk/vN+Hg X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,RATWARE_GECKO_BUILD=1.426 Subject: LF: Re: Ferrite wideband antennas? Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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=none 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-SCORE: 0:2:396895232:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d40924e5cff2c4607 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Hi again Daniele, I forgot some words about shielding. Do not use solid sheet. I just built a small receiver for rtty at 147 kHz for weather report reception when sailing. Using a fine looking u-shaped copper shield the signal went down of some 10 dB even if spaced 4 cm apart from the rod. And it did not improve the SNR considerably. Using an envelope from old SCSI flatline soldered together only at one side the SNR went up of >10 dB inside the house. The effect is incredible. My guess is that Eddy currents are responsible for this. So if possible shield your ferrite antenna coil by a "feathered", comb-like structure with multiple conductors running in parallel around the rod. They may overlap some cm if isolated. And in contrast to solid shielding distance doesn't matter. Peter, df3lp