X-GM-THRID: 1210068186790824898 X-Gmail-Labels: rsgb lf X-Gmail-Received: 4268100d27c82ab7579442bca961b57cdc52b71d Delivered-To: daveyxm@gmail.com Received: by 10.64.250.6 with SMTP id x6cs310898qbh; Thu, 27 Jul 2006 07:35:51 -0700 (PDT) Received: by 10.48.210.20 with SMTP id i20mr86553nfg; Thu, 27 Jul 2006 07:35:50 -0700 (PDT) Return-Path: Received: from post.thorcom.com ([193.82.116.20]) by mx.gmail.com with ESMTP id i1si3422340nfe.2006.07.27.07.35.37; Thu, 27 Jul 2006 07:35:50 -0700 (PDT) Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1G66re-0003gc-Sx for rs_out_1@blacksheep.org; Thu, 27 Jul 2006 15:29:26 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1G66re-0003gT-BJ for rsgb_lf_group@blacksheep.org; Thu, 27 Jul 2006 15:29:26 +0100 Received: from relay.dera.gov.uk ([192.5.29.49] helo=relay.dstl.gov.uk) by relay1.thorcom.net with smtp (Exim 4.62) (envelope-from ) id 1G66rb-0006zQ-9u for rsgb_lf_group@blacksheep.org; Thu, 27 Jul 2006 15:29:26 +0100 Received: (qmail 20497 invoked from network); 27 Jul 2006 15:29:17 +0100 Received: from warlock.dstl.gov.uk (192.5.29.10) by relay.dera.gov.uk with SMTP; 27 Jul 2006 15:29:17 +0100 Message-ID: <7D653C9C42F5D411A27C00508BF8803D06A1AC4A@mail.dstl.gov.uk> From: Talbot Andrew To: rsgb_lf_group@blacksheep.org Cc: Andy Talbot Date: Thu, 27 Jul 2006 15:29:38 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) X-Spam-Score: 0.5 (/) X-Spam-Report: autolearn=disabled,AWL=0.369,FORGED_RCVD_HELO=0.05,HTML_50_60=0.095,HTML_MESSAGE=0.001 Subject: LF: RE: Tapped loading coil design spreadshe et Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C6B189.174511DA" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.0 required=5.0 tests=HTML_30_40,HTML_FONTCOLOR_BLUE, HTML_FONTCOLOR_UNKNOWN,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 Status: O X-Status: X-Keywords: X-UID: 6204 This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------_=_NextPart_001_01C6B189.174511DA Content-Type: text/plain Could I have a copy of the tapped coil design info pse. Can you send to my other account andy.g4jnt@googlemail.com as the firewall here gets a bit upset with .xls attachments Andy G4JNT www.scrbg.org/g4jnt/ _____ From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of james moritz Sent: 27 July 2006 14:12 To: rsgb_lf_group@blacksheep.org Subject: LF: Tapped loading coil design spreadsheet Dear LF Group, I have been doing some investigation into the design of tapped loading coils for LF antennas - specifically, where to put the tap for the TX connection to achieve matching to 50 ohms. As far as I can see, there is no simple formula that gives a realistic result, and generally the tapping point is selected by trial and error. But it would be nice to know at least approximately where the taps should be, to take the guesswork out of making a coil. It appears that the tapping point can be calculated reasonably accurately (within about 10% resistance, or +/- 1 turn or so - assuming the antenna loss resistance is known), but it is quite a complicated and tedious process. So I have made an Excel spreadsheet that does all the coil design calculations, the user just has to enter the coil diameter, winding pitch and some other details, and the antenna capacitance, and gets a graph of matched antenna resistance vs. tapping point turns (and some other info, like the overall number of turns needed). I have tested the spreadsheet results against measurements of 3 real loading coils with different geometries, with the kind of results mentioned above. It is also quite easy to "reverse engineer" an existing loading coil. Some interesting results arose that I was not aware of previously. There is a definite upper limit to the antenna resistance that can be matched, which depends on the winding pitch and diameter of the coil. "Short, fat" loading coils, with large diameter and closely spaced turns, can match higher antenna resistances than "long, thin" coils. Any tapped coil can match resistances below the TX output resistance, if it has enough turns. But for lower antenna resistance, a "long, thin" coil offers the advantage of a smaller change in resistance between each tap, leading to a more accurate match. I have written a short article as a pdf file that explains how to fill in the spreadsheet, and showing the measured coil data, to go with the spreadsheet itself. These files are too big for the reflector, but let me know if you would like me to email them direct. I would be interested to know if others get reasonable agreement between the spreadsheet results and their loading coils - if you don't have Excel on your PC, let me know details of your coil (diameter, length, number of turns or winding pitch), and I can run the calculations for you. Cheers, Jim Moritz 73 de M0BMU "This e-mail is intended for the recipient only. If you are not the intended recipient you must not use, disclose, distribute, copy, print, or rely upon this e-mail. If an addressing or transmission error has misdirected this e-mail, please notify the author by replying to this e-mail." "Recipients should note that all e-mail traffic on MOD systems is subject to monitoring and auditing." ------_=_NextPart_001_01C6B189.174511DA Content-Type: text/html
Could I have a copy of the tapped coil design info pse.   Can you send to my other account  andy.g4jnt@googlemail.com as the firewall here gets a bit upset with .xls attachments
 
Andy  G4JNT

 

 

From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of james moritz
Sent: 27 July 2006 14:12
To: rsgb_lf_group@blacksheep.org
Subject: LF: Tapped loading coil design spreadsheet

Dear LF Group,

 

I have been doing some investigation into the design of tapped loading coils for LF antennas – specifically, where to put the tap for the TX connection to achieve matching to 50 ohms. As far as I can see, there is no simple formula that gives a realistic result, and generally the tapping point is selected by trial and error. But it would be nice to know at least approximately where the taps should be, to take the guesswork out of making a coil.

 

It appears that the tapping point can be calculated reasonably accurately (within about 10% resistance, or +/- 1 turn or so – assuming the antenna loss resistance is known), but it is quite a complicated and tedious process. So I have made an Excel spreadsheet that does all the coil design calculations, the user just has to enter the coil diameter, winding pitch and some other details, and the antenna capacitance, and gets a graph of matched antenna resistance vs. tapping point turns (and some other info, like the overall number of turns needed). I have tested the spreadsheet results against measurements of 3 real loading coils with different geometries, with the kind of results mentioned above. It is also quite easy to “reverse engineer” an existing loading coil.

 

Some interesting results arose that I was not aware of previously. There is a definite upper limit to the antenna resistance that can be matched, which depends on the winding pitch and diameter of the coil. “Short, fat” loading coils, with large diameter and closely spaced turns, can match higher antenna resistances than “long, thin” coils. Any tapped coil can match resistances below the TX output resistance, if it has enough turns. But for lower antenna resistance, a “long, thin” coil offers the advantage of a smaller change in resistance between each tap, leading to a more accurate match.

 

I have written a short article as a pdf file that explains how to fill in the spreadsheet, and showing the measured coil data, to go with the spreadsheet itself. These files are too big for the reflector, but let me know if you would like me to email them direct. I would be interested to know if others get reasonable agreement between the spreadsheet results and their loading coils – if you don’t have Excel on your PC, let me know details of your coil (diameter, length, number of turns or winding pitch), and I can run the calculations for you.

 

Cheers, Jim Moritz

73 de M0BMU

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