Return-Path: Received: from mtain-md10.r1000.mx.aol.com (mtain-md10.r1000.mx.aol.com [172.29.96.94]) by air-di06.mail.aol.com (v127_r1.1) with ESMTP id MAILINDI061-eaca4baa7b51224; Wed, 24 Mar 2010 16:51:29 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-md10.r1000.mx.aol.com (Internet Inbound) with ESMTP id AB7B1380000BA; Wed, 24 Mar 2010 16:51:27 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NuXWS-0006c1-1I for rs_out_1@blacksheep.org; Wed, 24 Mar 2010 20:49:52 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NuXWR-0006bs-CS for rsgb_lf_group@blacksheep.org; Wed, 24 Mar 2010 20:49:51 +0000 Received: from smtp817.mail.ukl.yahoo.com ([217.12.12.246]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1NuXWP-00014J-Ak for rsgb_lf_group@blacksheep.org; Wed, 24 Mar 2010 20:49:51 +0000 Received: (qmail 3147 invoked from network); 24 Mar 2010 20:49:43 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btopenworld.com; h=DKIM-Signature:Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MIMEOLE; b=CGpUnj1OgjEgX0SnZ1osaYlLGh+ZzEFZqeeHLUJIIZ66d1HHq7eUHiXZMdv8kOToi9JGguwoFQtTmZtkxTe/M03TzzTFrdPLJMvMWGh2Jpqf5ioQVVgFYg5VdowOvZ6jbUEij2/PuS2fxm78psD893AgerFbKjRLig3QN1sb4a4= ; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btopenworld.com; s=s1024; t=1269463783; bh=nE5gZ5+HyUCpco3SO9Qltj+weeVcc12+lIUHNaZSG9Q=; h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MIMEOLE; b=zUhjvm6KVWn6Lr2zJ10WxbVZeg7duh2eCVtdJC1lqaT6jb7YiYxpThI7Xocz62UHW+Mb/taDN3k9cuTpN+3PfYjbZMXWPd/1DJCHQ/Lx8xV3KNnXDyyvZLO9ODaLG5jwnZ51ZV32u3RyCLCvzEIyFsM5kqXz55iBT1XvatTeGlM= Received: from JimPC (james.moritz@86.180.204.156 with login) by smtp817.mail.ukl.yahoo.com with SMTP; 24 Mar 2010 20:49:43 +0000 GMT X-Yahoo-SMTP: Cxhli3eswBD1ozmtAojhjrja86kWx0Qm9tycD5QR1DKWrOLgjJcXkw-- X-YMail-OSG: 5azZBs4VM1mF.6zCOinZHqXs7CWlKmPgW47trl34wQ3YKLRoSlYRuxhiR5SuxN85uXhTjZiG55HwmQY2V1zkwiCUrXPm2X_ahOwwbBrOoHf1L1r2gdn9Jd5Gki.ejSDv3aZKDK79n305JJWuL8Wxz4aVhzXloaUbVOcd4Q23yAKhAyUF10VX_I7QBZTVPSEk4nN0eiqZ7ZSIdLF81y6jFFcDVxOl X-Yahoo-Newman-Property: ymail-3 Message-ID: From: "James Moritz" To: References: <2a2c8.24f60f40.38d54e4e@aol.com> <38A51B74B884D74083D7950AD0DD85E82A1B81@File-Server-HST.hst.e-technik.tu-darmstadt.de> <4BA5CFAA.2030007@freenet.de> <56800827A5644E1BB3F320CB51E2300E@Black> <26E279AD762E44FB937A8A7DF8F934BC@Black> <8C7F2923D86B4517B1C156BA499E96E4@Black> <29746320.1346347.1269244849281.JavaMail.fmail@mwmweb078> <4BA7361F.1030702@abelian.org> <4BA7A586.8080307@abelian.org> <38A51B74B884D74083D7950AD0DD85E82A1B87@File-Server-HST.hst.e-technik.tu-darmstadt.de> <0A742B5B9F6A4E84A802D1F98B670E79@JimPC> <20100323130953.2BEFC31E702@smtps01.kuleuven.be> In-Reply-To: Date: Wed, 24 Mar 2010 20:49:43 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18005 X-MIMEOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,UNPARSEABLE_RELAY=0.001 Subject: LF: Re: Mini-Whip Content-Type: text/plain; format=flowed; charset="ISO-8859-15"; reply-type=original 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=0.1 required=5.0 tests=MISSING_OUTLOOK_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-AUTHENTICATION: mail_rly_antispam_dkim-d277.2 ; domain : btopenworld.com DKIM : fail x-aol-sid: 3039ac1d605e4baa7b4f3358 X-AOL-IP: 193.82.116.20 Dear Roelof, LF Group, Thinking about your mini-whip design, it seems to me it might benefit from modification for VLF use. The circuit is a high Z buffer driven by the capacitive probe - the source impedance might be 10 - 20pF , if one includes the JFET follower input capacitance with the probe capacitance as part of the source. The reactance of 15pF at 9kHz is about 1.2Megohms. This is shunted via the bias resistors, totalling 1.5Megohms, so nearly 3dB loss of signal amplitude will occur relative to higher frequencies at 9k, or more at lower frequencies if one were to use the antenna for "natural radio" purposes - the resistors will also add to the input noise voltage. So for VLF use, higher value bias resistors might be appropriate. Alternatively, the probe capacitance could be increased. The band noise level may be so high that this doesn't make much difference in practice though, as far as SNR is concerned. Cheers, Jim Moritz 73 de M0BMU