Return-Path: Received: (qmail 21099 invoked from network); 11 Jan 2005 12:46:10 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore01.plus.net with SMTP; 11 Jan 2005 12:46:10 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CoLPD-000Fou-4O for dave@picks.force9.co.uk; Tue, 11 Jan 2005 12:45:53 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CoLPC-000Foe-Le for dave@picks.force9.co.uk; Tue, 11 Jan 2005 12:45:50 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1CoLPT-000MNO-Fo for dave@picks.force9.co.uk; Tue, 11 Jan 2005 12:46:07 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CoLOl-00032D-Qq for rs_out_1@blacksheep.org; Tue, 11 Jan 2005 12:45:23 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CoLOl-000324-F5 for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2005 12:45:23 +0000 Received: from gander.ucs.mun.ca ([134.153.232.65]) by relay.thorcom.net with esmtp (Exim 4.43) id 1CoLOf-00018d-RN for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2005 12:45:23 +0000 Received: from plato.ucs.mun.ca (root@plato.ucs.mun.ca [134.153.232.151]) by gander.ucs.mun.ca (8.12.10/8.12.10) with ESMTP id j0BCj0np031034 for ; Tue, 11 Jan 2005 09:15:00 -0330 Received: from plato.ucs.mun.ca (jcraig@localhost [127.0.0.1]) by plato.ucs.mun.ca (8.12.3p2/8.12.3) with ESMTP id j0BCixTW005625 for ; Tue, 11 Jan 2005 09:14:59 -0330 (NST) Received: (from jcraig@localhost) by plato.ucs.mun.ca (8.12.3p2/8.12.1/Submit) id j0BCixVe004737; Tue, 11 Jan 2005 09:14:59 -0330 (NST) Date: Tue, 11 Jan 2005 09:14:59 -0330 (NST) From: Joe Craig X-X-Sender: jcraig@plato.ucs.mun.ca To: rsgb_lf_group@blacksheep.org In-Reply-To: <41E2BD35.2010105@usa.net> Message-ID: References: <000001c4f735$272eea90$e6a4c593@RD40002> <41E2BD35.2010105@usa.net> MIME-Version: 1.0 X-Spam-Flag: NO X-Spam-Report: -10 USER_IN_WHITELIST From: address is in the user's white-list * -2.8 ALL_TRUSTED Did not pass through any untrusted hosts X-SPF-Result: relay.thorcom.net: 134.153.232.65 is neither permitted nor denied by domain of morgan.ucs.mun.ca X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=failed,none Subject: Re: LF: Re: Pre-amps on LF Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Content-transfer-encoding: 8bit Dear Jim and Alberto and LF group, Thank-you for the info. I well remember reading Alberto's article. The schematic of the FT-817 shows about 6 switching diodes and some shunt 100 uH chokes and series 0.1 uF caps. Fortunately, the internal preamp can be bypassed (by activiating the so called AIP) which improves the LF gain significantly. It appears as if the main culprit is indeed insufficient reactance of the transformer before the mixer. So we can replace the shunt chokes, pad the caps and replace the transformer, but the frustration level of having to do this at the SMT scale will be high. I think that this will also compromise the VHF an UHF performance of the RX. It is now starting to look easier to start from scratch by building a new LF RX or simply to continue using the external preamp. 73 Joe VO1NA On Mon, 10 Jan 2005, Alberto di Bene wrote: > james moritz wrote: > > > I'm sure some people have described mods > >where this transformer is changed to improve LF performance, but I can't > >think who at the moment. > > > > > http://www.mods.dk/view.php?ArticleId=2711 > > 73 Alberto I2PHD > > > >