Return-Path: Received: (qmail 41408 invoked from network); 10 Jan 2005 14:33:28 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore02.plus.net with SMTP; 10 Jan 2005 14:33:28 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1Co0bU-000NZv-S7 for dave@picks.force9.co.uk; Mon, 10 Jan 2005 14:33:13 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1Co0bU-000NZj-GE for dave@picks.force9.co.uk; Mon, 10 Jan 2005 14:33:08 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1Co0bh-000GQM-Je for dave@picks.force9.co.uk; Mon, 10 Jan 2005 14:33:21 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Co0aY-0007hG-4D for rs_out_1@blacksheep.org; Mon, 10 Jan 2005 14:32:10 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Co0aX-0007h7-OG for rsgb_lf_group@blacksheep.org; Mon, 10 Jan 2005 14:32:09 +0000 Received: from one.surfree.co.uk ([195.80.0.234]) by relay.thorcom.net with esmtp (Exim 4.43) id 1Co0aV-00057N-84 for rsgb_lf_group@blacksheep.org; Mon, 10 Jan 2005 14:32:09 +0000 Received: from standalone ([212.248.140.7]) by one.surfree.co.uk (8.9.3/8.9.3) with SMTP id PAA20973 for ; Mon, 10 Jan 2005 15:33:08 GMT Received: by localhost with Microsoft MAPI; Mon, 10 Jan 2005 14:31:41 -0000 Message-ID: <01C4F721.19B091C0.actalbot@southsurf.com> From: Andy To: "'rsgb_lf_group@blacksheep.org'" Date: Mon, 10 Jan 2005 14:31:38 -0000 Importance: high X-Priority: 1 (Highest) Organization: UKNWN(UK) X-Mailer: Microsoft Internet E-mail/MAPI - 8.0.0.4211 MIME-Version: 1.0 X-SPF-Result: relay.thorcom.net: 195.80.0.234 is neither permitted nor denied by domain of southsurf.com X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=failed,X_PRIORITY_HIGH=0.093 Subject: RE: LF: Re: 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=0.5 required=5.0 tests=X_PRIORITY_HIGH 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) Many receivers probably have a high pass filter to reduce strong broadcast signals below 1.6MHz Andy G4JNT On Monday, January 10, 2005 12:23 PM, jan-martin.noding@telenor.com [SMTP:jan-martin.noding@telenor.com] wrote: > Even 1N4148 doesn't add more attenuation than a fraction of dB. so I really > doubt the statement, the only real problem is possible intermodulation > > 73 > Jan-Martin, LA8AK > > -----Opprinnelig melding----- > Fra: owner-rsgb_lf_group@blacksheep.org > [mailto:owner-rsgb_lf_group@blacksheep.org]På vegne av Claudio Pozzi > Sendt: 10. januar 2005 11:46 > Til: rsgb_lf_group@blacksheep.org > Emne: Re: LF: Re: Pre-amps on LF > > > On Saturday 08 January 2005 17:48, Joe Craig wrote: > > Dear LF Group, > > > > Getting back to the FT-817, is it possible to > > modify the front end or first mixer so that > > a preamp would be unnecessary? > > Many RTX uses inexpensive diodes in the front-end design, for bandpass > filter and preamp and attenuator switching. > > Also if they used more expensive PIN diodes those devices are not the > best switching devices for LF. A 100 kHz PIN diode switching devices > require a minority carrier lifetime of few ten's of microseconds. If > the life time is shorter the diodes acts as a rectifier, not as a > switch. I don't know many PIN diodes useful in LF band. > > So I think that the problem is not in the mixer but in band switching > devices. > > 73 de Claudio, ik2pii > > -- > Claudio Pozzi - Happy Linux User - http://www.qsl.net/ik2pii > > > > > > > > -- > > Email.it, the professional e-mail, gratis per te: http://www.email.it/f > > > > Sponsor: > > Migliaia di manuali e guide scaricabili su: Office, Webmaster, Internet, > Windows e non solo...clicca qui > > Clicca qui: http://adv.email.it/cgi-bin/foclick.cgi?mid=2731&d=10-1