Return-Path: Received: (qmail 26428 invoked from network); 19 Dec 2002 18:03:33 -0000 Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 19 Dec 2002 18:03:33 -0000 Content-Transfer-Encoding: 8bit Received: (qmail 21377 invoked from network); 19 Dec 2002 18:03:27 -0000 X-Priority: 3 Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 19 Dec 2002 18:03:27 -0000 X-MSMail-Priority: Normal X-SQ: A X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from majordom by post.thorcom.com with local (Exim 4.10) id 18P4zi-0008Ui-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 19 Dec 2002 18:02:02 +0000 Received: from [212.125.75.12] (helo=mail4.messagelabs.com) by post.thorcom.com with smtp (Exim 4.10) id 18P4ze-0008UZ-00 for rsgb_lf_group@blacksheep.org; Thu, 19 Dec 2002 18:01:59 +0000 X-VirusChecked: Checked X-Env-Sender: William.Ashlock@edwards.boc.com X-Msg-Ref: server-9.tower-4.messagelabs.com!1040320916!41505 Received: (qmail 24286 invoked from network); 19 Dec 2002 18:01:56 -0000 Received: from unknown (HELO ukfw1.ge.boc.com) (193.131.2.157) by server-9.tower-4.messagelabs.com with SMTP; 19 Dec 2002 18:01:56 -0000 Received: from z-160-100-160-136.est.ibm.com ([160.100.160.136]) by ukfw1.ge.boc.com; Thu, 19 Dec 2002 18:01:49 +0000 (GMT) Received: from exc_wil04.edwards.boc.com ([162.118.144.226]) by exc_cra03.edwards.boc.com with SMTP (Microsoft Exchange Internet Mail Service Version 5.5.2653.13) id YSKVTCR8; Thu, 19 Dec 2002 18:05:37 -0000 Received: by EXC_WIL04 with Internet Mail Service (5.5.2653.19) id ; Thu, 19 Dec 2002 13:01:49 -0500 Message-ID: From: "Ashlock,William" To: rsgb_lf_group@blacksheep.org Date: Thu, 19 Dec 2002 13:01:44 -0500 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Subject: RE: LF: Big vs small RX antennas Content-Type: text/plain; charset=iso-8859-1; format=flowed X-Spam-Status: No, hits=-0.1 required=5.0tests=EXCHANGE_SERVER,INVALID_MSGID,QUOTED_EMAIL_TEXT, SPAM_PHRASE_00_01version=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group > Not so sure about the balanced pre-amp, it doesn't makes double balance, only one stage should be centered, when the > aerial is balanced - the connection to one side is just as good as balanced connection, the only improvement you can add >is better linearity. The only result of a balanced amplifier is that it is more difficult to make, but probably isn't so balanced > after all. > As long as the background noise without pre-amplifier is 10-20dB above the background band noise > it is totally waste to use a pre-amplifier, it may only worsening the result. I don't buy this. The reason for the balanced connection (or center tap) to the loop is to reduce the so called 'antenna effect'. Without the balance the antenna will be sensitive to the E-field of the intended signal as well as all the other unwanted signals and noise in the area, coming from all directions. Also, the desired null off the side, typically 40db for a well balanced loop, will be greatly reduced if the loop is connected simply to one side. One common way to achieve a 'balance' is to isolate the tuned winding from the input to the amplifier with a one or two turn isolated pickup winding. A ferrite core can also be used that couples one turn from the main winding to the amplifier or receiver. John Andrews uses this approach. I call both of these a 'floating connection' rather than a balanced connection', but they achieve the same thing because neither is effected by E-field signals. Bill A _____________________________________________________________________ This e-mail has been scanned for viruses by the WorldCom Internet Managed Scanning Service - powered by MessageLabs. For further information visit http://www.worldcom.com