Return-Path: Received: (qmail 19274 invoked from network); 19 Nov 1999 19:59:56 +0000 Received: from unknown (HELO cask.force9.net) (195.166.128.29) by guiness.force9.net with SMTP; 19 Nov 1999 19:59:56 +0000 Received: (qmail 31168 invoked from network); 19 Nov 1999 19:59:59 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by cask.force9.net with SMTP; 19 Nov 1999 19:59:59 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11otb9-0004w3-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 19 Nov 1999 19:21:32 +0000 Received: from mb04.swip.net ([193.12.122.208]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11otb9-0004vy-00 for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 1999 19:21:31 +0000 Received: from oemcomputer (d212-151-86-119.swipnet.se [212.151.86.119]) by mb04.swip.net (8.8.8/8.8.8) with SMTP id UAA14006 for ; Fri, 19 Nov 1999 20:21:07 +0100 (MET) Message-ID: <00b501bf32c3$6e1d78e0$775697d4@oemcomputer> From: "Johan Bodin" To: rsgb_lf_group@blacksheep.org Subject: LF: SV: Receivers and power-line noise Date: Fri, 19 Nov 1999 20:21:54 +0100 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 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hello, Kevin Ravenhill wrote: >I have found out the hard way that the rectifier diodes in some power >supplies can generate truly enormous amounts of harmonic hash at these >frequencies. Not only on LF! Sometimes it is a problem on HF too. Many direct conversion receivers suffer from hum problems when powered from a mains supply, no matter how well regulated the supply is. There is more hum when using unbalanced antennas. The reason seems to be that local oscillator energy is leaking out on the antenna and some of this signal finds its way back to ground through the PSU rectifier. The signal is "chopped" by the rectifier diodes at the mains frequency (much like a sub-harmonic mixer) and the result is hum sidebands. The problem can often be solved by putting 0.1 uF capacitors across each rectifier diode. 73 de Johan, SM6LKM