Return-Path: Received: (qmail 21332 invoked from network); 19 Dec 2002 00:48:40 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 19 Dec 2002 00:48:40 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 27676 invoked from network); 19 Dec 2002 00:48:36 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 19 Dec 2002 00:48:36 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.10) id 18OorA-0004Rx-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 19 Dec 2002 00:48:08 +0000 Received: from [152.163.225.99] (helo=imo-r03.mx.aol.com) by post.thorcom.com with esmtp (Exim 4.10) id 18Oor9-0004Ro-00 for rsgb_lf_group@blacksheep.org; Thu, 19 Dec 2002 00:48:07 +0000 Received: from MarkusVester@aol.com by imo-r03.mx.aol.com (mail_out_v34.13.) id l.ba.329865bc (25508) for ; Wed, 18 Dec 2002 19:47:32 -0500 (EST) From: MarkusVester@aol.com Message-ID: Date: Wed, 18 Dec 2002 19:47:32 EST To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: AOL 7.0 for Windows DE sub 10501 Subject: LF: Big vs small RX antennas Content-Type: text/html; charset=windows-1252 X-Spam-Status: No, hits=1.9 required=5.0tests=NO_REAL_NAME,SPAM_PHRASE_00_01,USER_AGENT_AOLversion=2.42 X-Spam-Level: * Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Content-transfer-encoding: 8bit Hi John and LF group,

Just curious -- since the signal to noise ratio in my receiving installation
appears to be limited by external (man-made and atmospheric) noise, rather
than noise in my preamp/receiver, how would a 100 foot tower improve that
situation?

John Andrews, W1TAG


A big vertical does help a lot against local noise-sources (neighbours' TVs and SMPSs), but with anything originating further away than a couple of 100m, it makes absolutely no difference.

However the directivity provided by a magnetic receive loop can be valuable. If all of the noise was coming in isotropically from the horizon, the figure-eight pattern would theoretically have 3dB better SNR than a vertical, and a cardioid combination would gain 4.8dB. In practice, of course one can often null out a source of QRM or a thunderstorm front and have far greater improvement.

The only problem I am having with small loops is that they seem to be much more prone to local pickup than the E-field antenna - at least in my suburban area which has underground mains wiring. The 86cm-diameter pair in the garden is often swamped by notorious 100Hz-modulated carriers which at the same time I can hardly see on the marconi.

73 de
Markus, DF6NM