Return-Path: Received: from mtain-dh01.r1000.mx.aol.com (mtain-dh01.r1000.mx.aol.com [172.29.65.21]) by air-mc02.mail.aol.com (v129.10) with ESMTP id MAILINMC022-a8d44dd015f12e3; Sun, 15 May 2011 14:05:37 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh01.r1000.mx.aol.com (Internet Inbound) with ESMTP id E84CA38000096; Sun, 15 May 2011 14:05:35 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QLffx-0000S1-8U for rs_out_1@blacksheep.org; Sun, 15 May 2011 19:04:21 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QLffw-0000Rs-Cg for rsgb_lf_group@blacksheep.org; Sun, 15 May 2011 19:04:20 +0100 Received: from mail-yx0-f171.google.com ([209.85.213.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QLfft-0000pb-Nq for rsgb_lf_group@blacksheep.org; Sun, 15 May 2011 19:04:20 +0100 Received: by yxe42 with SMTP id 42so1838294yxe.16 for ; Sun, 15 May 2011 11:04:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; bh=zdM4imk1cwizl9XOC74NZtZr4WM/LC+nRIrPvs57sdc=; b=LRXgbpwEe9c+AN8jpjVVkoE0OafORTIUq33S2hKpr64vOxqAt4kHwazk5wUmhT88fK aH42nJ46bj+m3NnUZAmTvmXZvVJz/B5y7FeMnSioLt5W9BUomNe45bo4ThAX7JsMaGCz UXSJHgUyJGO72pk+hC8k9vWjkQmFqO0jPRGho= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=uliZAKMOK3sLeYHIDHkCxt4s6k6G6+p5++7boCv9T8Cl5yl8QYJ8XzV824p/Sey1/i jIt06QWxcElt3OeJHcw6vDpgVwDGI0oSMI6I76G1iwZEM3r0kKNRxnXqAYvk//Fw2ApG 0Y5Jf4pG862AIGUpjprn+UNOEB7pxWNu0Zxl4= MIME-Version: 1.0 Received: by 10.101.148.37 with SMTP id a37mr1993674ano.150.1305482649930; Sun, 15 May 2011 11:04:09 -0700 (PDT) Received: by 10.100.210.9 with HTTP; Sun, 15 May 2011 11:04:09 -0700 (PDT) In-Reply-To: <4DD009E3.3060503@iup.uni-heidelberg.de> References: <80703.53770.qm@web28515.mail.ukl.yahoo.com> <4DCEDBB3.1020808@iup.uni-heidelberg.de> <4DCFA642.5070305@m0dts.co.uk> <4DD009E3.3060503@iup.uni-heidelberg.de> Date: Sun, 15 May 2011 19:04:09 +0100 X-Google-Sender-Auth: qxUZKiDFpjDFPtCgp_MRYIFMU5A Message-ID: From: Gary - G4WGT To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: LF SWR Bridge Content-Type: multipart/alternative; boundary=0016e68ee1369c0ade04a3545d56 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE 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-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d006.1 ; domain : gmail.com DKIM : fail x-aol-sid: 3039ac1d41154dd015ef34ca X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --0016e68ee1369c0ade04a3545d56 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hello Rob & Stefan, That is the one I used & I can highly recommend it. I have now changed to using the "ScopeMatch" tuning aid which is in "The Low Frequency Experimenters Handbook" by the same author. Of course you will require an oscilloscope for the display but I find it more accurate & very easy to us= e. Construction is very simple. If you wish to see the article (with other tuning aids) I will place it on my web site for down load, size is 2.6Mb. 73 Gary - G4WGT. 2011/5/15 Stefan Sch=E4fer > Hello Rob, > > Instead of a SWR bridge i would recommend a voltage/current and a phase > meter. The voltage/current ratio should be 50:1, so you can easily check= for > 50 Ohm. As i started with LF in 2003 i found that pdf from Jim/M0BMU wit= h a > good description. The advantage of that tuning meter is that you can see= if > the mismatch is caused by a reactive part (=3D not in resonance) or due= to an > impedance that is not equal to 50 Ohm. > I'm not sure if the link is still working but i found the pdf in my old= LF > folder and put it to http://dl.dropbox.com/u/19882028/LF/LFtunemeter.pdf= ...if you want to take a look there... > > 73, Stefan/DK7FC > > > > Am 15.05.2011 12:09, schrieb Rob, M0DTS: > > 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 aga= in > 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 > > --0016e68ee1369c0ade04a3545d56 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hello Rob & Stefan,

That is the one I used & I= can highly recommend it. I have now changed to using the "ScopeMatch= " tuning aid which is in "The Low Frequency Experimenters Handbo= ok" by the same author. Of course you will require an oscilloscope fo= r the display but I find it more accurate & very easy to use. Construc= tion is very simple.

If you wish to see the article (with other tuning aids= ) I will place it on my web site for down load, size is 2.6Mb.
<= br>
73

Gary - G4WGT.


2011/5/15 Stefan Sch=E4fer &l= t;schaefer@iup.uni-heide= lberg.de>
=20
Hello Rob,

Instead of a SWR bridge i would recommend a voltage/current and a phase meter. The voltage/current ratio should be 50:1, so you can easily check for 50 Ohm. As i started with LF in 2003 i found that pdf from Jim/M0BMU with a good description. The advantage of that tuning meter is that you can see if the mismatch is caused by a reactive part (=3D not in resonance) or due to an impedance that is not equal to 50 Ohm.
I'm not sure if the link is still working but i found the pdf in my ol= d LF folder and put it to http://dl.dropbox.com/u/19882028/LF/LFtunemeter.pdf ...if you= want to take a look there...

73, Stefan/DK7FC



Am 15.05.2011 12:09, schrieb Rob, M0DTS:
=20 =20 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..=A0 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,=A0 a very small one (13mm) but i should be able= to get the same effect I'm sure,=A0 i just can't get any difference= between forward/reflect at all with 50R on the load port..=A0 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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