Return-Path: Received: (qmail 30597 invoked from network); 16 Apr 2003 09:05:35 -0000 Received: from marstons.services.quay.plus.net (212.159.14.223) by mailstore with SMTP; 16 Apr 2003 09:05:35 -0000 Received: (qmail 29899 invoked by uid 10001); 16 Apr 2003 09:05:35 -0000 Received: from post.thorcom.com (193.82.116.70) by marstons.services.quay.plus.net with SMTP; 16 Apr 2003 09:05:35 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.14) id 195iqJ-0004nj-RV for rsgb_lf_group-outgoing@blacksheep.org; Wed, 16 Apr 2003 10:04:35 +0100 Received: from [62.253.162.47] (helo=mta07-svc.ntlworld.com) by post.thorcom.com with esmtp (Exim 4.14) id 195iqE-0004na-TI for rsgb_lf_group@blacksheep.org; Wed, 16 Apr 2003 10:04:31 +0100 Received: from mike1 ([80.4.107.45]) by mta07-svc.ntlworld.com (InterMail vM.4.01.03.37 201-229-121-137-20020806) with ESMTP id <20030416090430.PITG25105.mta07-svc.ntlworld.com@mike1> for ; Wed, 16 Apr 2003 10:04:30 +0100 Message-ID: <001001c303f7$43b8dd20$2602a8c0@WorkGroup> From: "mike.dennison" To: rsgb_lf_group@blacksheep.org References: <001e01c30389$be512e20$97d2fc3e@ian> <000b01c303a8$9a95bf40$07c828c3@erica> Date: Wed, 16 Apr 2003 10:05:00 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: The Mystery Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-22.8 required=5.0tests=EMAIL_ATTRIBUTION,QUOTED_EMAIL_TEXT,REFERENCES, REPLY_WITH_QUOTESversion=2.53 X-Spam-Checker-Version: SpamAssassin 2.53 (1.174.2.15-2003-03-30-exp) X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false G3LDO wrote: > It wasn't always so. When I used the BK amp originally I used a tapped > loading coil arangement and got some strange effects. Things got better when > I started using a multi-tapped torroid transformer, which isolated the BK > amp from the antenna system. This transformer was located at the base of the > coil and fed at 4ohms from the amp using heavy duty electrical cable. The BK > amplifier is prone to instability when experimenting with different loads. > This is caused by the high gain of the amplifier (the negative feedback > might also become positive feedback with some loads) and could be fixed by > putting some heavy resistive loading at the input of the amplifier. That's exactly my experience. Since using toroidal transformers and a resistor across the input I have a very stable BK amp. I use the amp on 73kHz (though it will, of course, also run on 136 if I want) and I have a toroid to take the impedance from 4ohms to about 50 ohms, then this feeds a multitapped toroidal transformer that I use on 136kHz to take the Decca from 50ohms to the 150-200ohms of the antenna system. Since the final output is completely isolated, any current is due to the earths that I know about, not any stray earthing through the rig. In the history of my station, one of the great breakthroughs (several years ago) was to separate the matching and resonating. They can be done together but it leads to much fiddling and some confusion as to what is happening. Mike, G3XDV http://www.lf.thersgb.net ====================