Return-Path: Received: from mtain-dl06.r1000.mx.aol.com (mtain-dl06.r1000.mx.aol.com [172.29.74.212]) by air-da07.mail.aol.com (v129.10) with ESMTP id MAILINDA072-86174dcfa6822cd; Sun, 15 May 2011 06:10:10 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dl06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9D86C380000B1; Sun, 15 May 2011 06:10:09 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QLYGB-0007bc-MO for rs_out_1@blacksheep.org; Sun, 15 May 2011 11:09:15 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QLYGB-0007bS-8g for rsgb_lf_group@blacksheep.org; Sun, 15 May 2011 11:09:15 +0100 Received: from yoda.london.02.net ([82.132.130.151] helo=mail.o2.co.uk) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QLYG9-0001n7-52 for rsgb_lf_group@blacksheep.org; Sun, 15 May 2011 11:09:15 +0100 Received: from [192.168.1.122] (87.194.98.211) by mail.o2.co.uk (8.5.119.05) (authenticated as m0dts@o2.co.uk) id 4C9F76EE3621C4D0 for rsgb_lf_group@blacksheep.org; Sun, 15 May 2011 11:09:07 +0100 Message-ID: <4DCFA642.5070305@m0dts.co.uk> Date: Sun, 15 May 2011 11:09:06 +0100 From: "Rob, M0DTS" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <80703.53770.qm@web28515.mail.ukl.yahoo.com> <4DCEDBB3.1020808@iup.uni-heidelberg.de> In-Reply-To: X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: LF: LF SWR Bridge Content-Type: multipart/alternative; boundary="------------000906000006040505050005" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_MESSAGE,HTML_TITLE_EMPTY 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-aol-global-disposition: G x-aol-sid: 3039ac1d4ad44dcfa68104d2 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --------------000906000006040505050005 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi All.. I'm trying to put together my 137KHz transmitter after it has gathered dust in the loft for a few years and will hopefully generate some signals again soon.. I'm not so good with this LF so need a bit of help with an swr bridge.. This will stop me blowing FET's this time i hope! I've seen a couple of designs for an swr bridge and have tried out G0MRF's one here which appears so simple who could go wrong?! I'm using a 3c90 core, a very small one (13mm) but i should be able to get the same effect I'm sure, i just can't get any difference between forward/reflect at all with 50R on the load port.. the only difference i have in my build is the different core size. I've tried increasing the bifiliar turns but just gave more coupling as you would expect.. I guess I'm just very low on inductance by using the different core so the q is too low and i don't 'see' the dip in reflected signal when tuned? Any ideas and a simple explanation of how it works would be useful.. Thanks Rob M0DTS --------------000906000006040505050005 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi All..

I'm trying to put together my 137KHz transmitter after it has gathered dust in the loft for a few years and will hopefully generate some signals again soon..
I'm not so good with this LF so need a bit of help with an swr bridge.. This will stop me blowing FET's this time i hope!

I've seen a couple of designs for an swr bridge and have tried out G0MRF's one here which appears so simple who could go wrong?!

I'm using a 3c90 core, a very small one (13mm) but i should be able to get the same effect I'm sure, i just can't get any difference between forward/reflect at all with 50R on the load port.. the only difference i have in my build is the different core size.
I've tried increasing the bifiliar turns but just gave more coupling as you would expect..

I guess I'm just very low on inductance by using the different core so the q is too low and i don't 'see' the dip in reflected signal when tuned?

Any ideas and a simple explanation of how it works would be useful..

Thanks

Rob
M0DTS

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