Return-Path: Received: (qmail 29519 invoked from network); 16 Jun 1999 21:09:01 +0100 Received: from unknown (HELO magnet.force9.net) (195.166.128.26) by guiness.force9.net with SMTP; 16 Jun 1999 21:09:01 +0100 Received: (qmail 18564 invoked from network); 16 Jun 1999 18:46:50 -0000 Received: from unknown (HELO post.thorcom.com) (194.75.130.70) by magnet.plus.net.uk with SMTP; 16 Jun 1999 18:46:50 -0000 Received: from troy.blacksheep.org ([194.75.183.50] ident=root) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10uBoz-0006Wx-00; Wed, 16 Jun 1999 10:17:25 +0100 Received: (from root@localhost) by troy.blacksheep.org (8.6.12/8.6.12) id JAA23134 for rsgb_lf_group-outgoing; Wed, 16 Jun 1999 09:15:10 GMT Received: from post.thorcom.com (root@post.unica.co.uk [194.75.183.70]) by troy.blacksheep.org (8.6.12/8.6.12) with ESMTP id JAA23130 for ; Wed, 16 Jun 1999 09:15:07 GMT Received: from mb04.swip.net ([193.12.122.208]) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10uBmT-0006We-00 for rsgb_lf_group@blacksheep.org; Wed, 16 Jun 1999 10:14:50 +0100 Received: from s-257519 (dialup56-2-57.swipnet.se [130.244.56.121]) by mb04.swip.net (8.8.8/8.8.8) with SMTP id LAA21557 for ; Wed, 16 Jun 1999 11:14:45 +0200 (MET DST) Message-ID: <006201beb7d8$a65bb700$fcf8f482@s-257519> From: "Johan Bodin" To: rsgb_lf_group@blacksheep.org Subject: SV: LF: Antennas, bandwidth, etc Date: Wed, 16 Jun 1999 11:13:52 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Bob ZL2CA wrote: >Also note that it is ineffective to use a separate noise receiver to >derive noise blanking drive, as it does not "reverse" the situation that >once a noise spike has become a noise blob (due to band limiting) then >the process can not be reversed, and the noise blob passes through the >receiver to the demodulator. I guess the "noise blob" you mentioned is the exponentially decaying ringing which occurs when a high Q antenna, such as a tuned loop, is excited by a short noise spike. As far as I understand, the traditional way is to put a switch somewhere in the signal path that opens up during the blanking pulse. This pulse has to be quite long if a high Q antenna is used (long blob). I think it is possible to kill that blob right at the antenna by using a separate wideband noise receiver and feed the blanking pulse to a switch (analog switch, fet or something) connected ACROSS the loop. This will "eat" the pulse energy almost instantly and the blanking pulse width can be made much shorter than in the "traditional" case. Has anyone tried this idea? 73 de Johan Bodin, SM6LKM