Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-db05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 605B5380001C1; Thu, 1 Sep 2011 12:22:59 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QzA1S-00014o-Ub for rs_out_1@blacksheep.org; Thu, 01 Sep 2011 17:21:46 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QzA1S-00014f-H3 for rsgb_lf_group@blacksheep.org; Thu, 01 Sep 2011 17:21:46 +0100 Received: from smtp04.online.nl ([194.134.41.34]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QzA1Q-0002iQ-5J for rsgb_lf_group@blacksheep.org; Thu, 01 Sep 2011 17:21:46 +0100 Received: from smtp04.online.nl (localhost [127.0.0.1]) by smtp04.online.nl (Postfix) with ESMTP id 1CF5CE0F5 for ; Thu, 1 Sep 2011 18:21:43 +0200 (CEST) Received: from pa3fnytrqxpddu (s529d275f.adsl.wanadoo.nl [82.157.39.95]) by smtp04.online.nl (Postfix) with SMTP for ; Thu, 1 Sep 2011 18:21:43 +0200 (CEST) From: To: Date: Thu, 1 Sep 2011 18:21:42 +0200 Message-ID: MIME-Version: 1.0 X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2911.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 In-Reply-To: <4E5F8F83.7050404@legal-medicine.de> X-Online-Scanned: by Cloudmark authority (on smtp04.online.nl) X-Spam-Score: 0.6 (/) X-Spam-Report: autolearn=disabled,NO_REAL_NAME=0.55 Subject: RE: LF: Re: Ferrite wideband antennas? Content-Type: text/plain; charset="iso-8859-1" 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=1.2 required=5.0 tests=FROM_ENDS_IN_NUMS,NO_REAL_NAME 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: 0:2:356841792:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d40594e5fb1623de3 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Hi Peter, try a BFP640,rBB 1ohm.Noise as low as 300pV/sqrt(Hz) is possible.Very cheap,but one drawback,Ft is about 40GHz,not easy to get stable.For topband I use BD139 (yes a lf driver),rbb 1,2 Ohm,very easy to use.. GL,73 Victor PA3FNY -----Oorspronkelijk bericht----- Van: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]Namens pws Verzonden: donderdag 1 september 2011 15:58 Aan: rsgb_lf_group@blacksheep.org Onderwerp: Re: LF: Re: Ferrite wideband antennas? Hi Jim, You wrote: > ... > I would be interested to know what method you used to determine SNR for the > different rod configurations. > ... Simply by going the broadband way and using a very low noise, very low impedance pre-amplifier. It's easy to get voltage noises below 1nV/sqrt(Hz) by running some transistors in parallel. Today I know that it's a low "Rbb" of the transistor type what makes the difference. Unfortunately it's hard to find this value in datasheets. I remember using BC327 or BC337 running at ~10mA each. Fortunately current noise doesn't matter here. The antennas had an inductance elsewhere around 0.5 mH. So the self resonances lowered by 200-300pF added by the transistors had been at least 1 octave above the region of interest. Obtaining spectra at a quiet spot will immediately showed the differences of SNRs since some constant signals were available not influenced by the ionosphere e.g. 147 kHz or Loran-C. I had/have such quiet spot here for field-days, a constructor's trailer made of sheet included. This was of importance for shielding the computer. Checking the depths of *both* "nulls" will give some hints about the balance. Peter, df3lp