Return-Path: Received: (qmail 51964 invoked from network); 11 Jan 2005 14:02:35 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore01.plus.net with SMTP; 11 Jan 2005 14:02:35 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CoMbB-000Egc-Re for dave@picks.force9.co.uk; Tue, 11 Jan 2005 14:02:18 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CoMbB-000EgZ-Mh for dave@picks.force9.co.uk; Tue, 11 Jan 2005 14:02:17 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1CoMbR-000Lft-VM for dave@picks.force9.co.uk; Tue, 11 Jan 2005 14:02:34 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CoMaZ-0003I6-Fh for rs_out_1@blacksheep.org; Tue, 11 Jan 2005 14:01:39 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CoMaX-0003Hx-2V for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2005 14:01:37 +0000 Received: from virus-out-st.online.no ([193.212.240.200] helo=scan.telenor.net) by relay.thorcom.net with esmtp (Exim 4.43) id 1CoMaQ-0001Km-G0 for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2005 14:01:37 +0000 Received: from tns-fbu-22-208.corp.telenor.no ([134.47.162.90] [134.47.162.90]) by scan.telenor.net with ESMTP for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2005 14:59:45 +0100 Received: from tns-fbu-22-213.corp.telenor.no ([134.47.162.191]) by tns-fbu-22-208.corp.telenor.no with Microsoft SMTPSVC(5.0.2195.6713); Tue, 11 Jan 2005 14:59:36 +0100 Received: from TNS-FBU-2E-014.corp.telenor.no ([134.47.163.124]) by tns-fbu-22-213.corp.telenor.no with Microsoft SMTPSVC(5.0.2195.6713); Tue, 11 Jan 2005 14:59:36 +0100 X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Content-class: urn:content-classes:message Date: Tue, 11 Jan 2005 14:59:35 +0100 Message-Id: Thread-Topic: LF: Re: Pre-amps on LF thread-index: AcT327jRQfvwbPbFQqmW1Ikm9PmRKgACYzVA From: jan-martin.noding@telenor.com To: rsgb_lf_group@blacksheep.org X-OriginalArrivalTime: 11 Jan 2005 13:59:36.0343 (UTC) FILETIME=[C8E7EA70:01C4F7E5] MIME-Version: 1.0 X-SPF-Result: relay.thorcom.net: 193.212.240.200 is neither permitted nor denied by domain of telenor.com X-Spam-Score: 0.2 (/) X-Spam-Report: autolearn=no,FORGED_RCVD_HELO=0.05,NO_REAL_NAME=0.178 Subject: LF: Re: semiconductor switches, was "Pre-amps on LF" Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.3 required=5.0 tests=NO_REAL_NAME 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) 100µH has reactance = 80 ohms, and 0.1µF has 12.5 ohm, so it isn't dramatic extra attenuation for the 6 switches, possibly around 10-15 dB in a 50 ohm system, or did I make wrong calculation? Jan-Martin, LA8AK -----Opprinnelig melding----- Fra: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]På vegne av Joe Craig Sendt: 11. januar 2005 13:45 Til: rsgb_lf_group@blacksheep.org Emne: Re: LF: Re: Pre-amps on LF 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 > > > >