Return-Path: Received: (qmail 7131 invoked from network); 17 Dec 2001 10:12:10 -0000 Received: from unknown (HELO warrior.services.quay.plus.net) (212.159.14.227) by excalibur-qfe1-smtp-plusnet.harl.plus.net with SMTP; 17 Dec 2001 10:12:10 -0000 Received: (qmail 353 invoked from network); 17 Dec 2001 10:12:15 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior.services.quay.plus.net with SMTP; 17 Dec 2001 10:12:15 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 16FufX-0005nJ-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 17 Dec 2001 10:06:47 +0000 Received: from tungsten.btinternet.com ([194.73.73.81]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 16FufT-0005nE-00 for rsgb_lf_group@blacksheep.org; Mon, 17 Dec 2001 10:06:43 +0000 Received: from host213-122-240-11.btinternet.com ([213.122.240.11] helo=default) by tungsten.btinternet.com with smtp (Exim 3.22 #8) id 16FueY-00053r-00 for rsgb_lf_group@blacksheep.org; Mon, 17 Dec 2001 10:05:47 +0000 Message-ID: <000001c186e2$62743b80$0bf07ad5@default> From: "Alan Melia" To: "LF-Group" Subject: LF: A Matching LPF Date: Sun, 16 Dec 2001 23:29:03 -0000 MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="------------020107060007030309040109" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: This is a multi-part message in MIME format. --------------020107060007030309040109 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Hi all, by way of a Christmas present to the group, I have attached a diagram of an L-Pi LPF design. The idea is that the filter offers both low pass filtering and also will match a PA output impedance (quite often in the 4 to 10 ohms range) to 50 ohms as well. This approach can avoid one transformer and one more variable in the tune-up process. If anyone wants to play the design is done using the disc in Wes Haywards "Intro to RF Design" with the program ZMAT I have used it in a successful Class E stage lash-up, so it does work. It is suggested that air cored coils and pulse rated capacitors are used. I used ordinary 400v caps and iron-dust cores and they did get warm at 150 watts. Also a Smith Chart simulation confirms that a few switched caps on the output (C2) could help to tweak it for best match to an aerial that is not exactly 50 ohms. Happy Chrismas de Alan G3NYK alan.melia@btinternet.com --------------020107060007030309040109 Content-Type: image/gif; name="L-PIMA~1.gif" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="L-PIMA~1.gif" R0lGODdhJAGAAYAAAAAAAP///ywAAAAAJAGAAQAC/oyPqcvtD6OctNqLs968+w+G4kiW5omm 6sq27gvH8kzX9o3n+s73vgwAVILEIiLYICaREmHTuWCKpK2iNWa9BqTcEzWSNRq+R6VCDCEv 1yN1Kmx2wZlcp/tzZ5DjDnQ5XzYBSDJICHXAt1I4ZnfY5pgGuSV5JiRpSVkpmGmyOHXJWeJJ F8rhyRjVuPaFRJWF6DfpijkLKwtpdDfox5qgC/qXeIsbq8k2Oeyb2Fp4imz8+2xLGsYYV22t JQ0XXGy79CotG6gHPMwbni1MXj6Nxq1eKg5GrNq+5Ys6X6cM2whlpg5AftaOpWJ3iA+nPaT6 6fvGKtOcb88iIjzlbM5A/jYEoz3cZw/iRnIW7x102GVkOXgmPT7Bti3kvIry2Cl7x3KmyJ03 CX50yBPkT5fGSKpqmG5iqmvFtPVZOHIWvIyUkoZyCZAiy1om9fn06ogoUK2YkFFjGinduYRq i56k2U0L1SFXJW7siPaj2IZDZer8afMhM7N1H+BcCUosUL6AA0eia9iuu6CC2aIMG7Jkybdu 9eIb8/lp5LGdHVN8y/hvY9EUABG1ZPTP6Zh+GW8WaNBtxIGlXLNVCZa0abJ9ZatG7LS08NMK /1kVeDh28Xi/YOYcV3D0U5hr40JlTRN69E3clQ8X19yfbalcg26+pVqp+pbydolhX883eNzd 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