Envelope-to: dave@picks.force9.co.uk Delivery-date: Thu, 03 Nov 2005 16:33:58 +0000 Received: by ptb-mxcore03.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1EXi2H-0002oK-Bj for dave@picks.force9.co.uk; Thu, 03 Nov 2005 16:33:58 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (PlusNet MXCore v2.00) id 1EXi2H-0002oB-3f for dave@picks.force9.co.uk; Thu, 03 Nov 2005 16:33:57 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1EXi1g-0008Nb-Tm for rs_out_1@blacksheep.org; Thu, 03 Nov 2005 16:33:20 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1EXi1g-0008NS-Dd for rsgb_lf_group@blacksheep.org; Thu, 03 Nov 2005 16:33:20 +0000 Received: from nibbel.kulnet.kuleuven.ac.be ([134.58.240.41]) by relay1.thorcom.net with esmtp (Exim 4.51) id 1EXino-0002qG-0R for rsgb_lf_group@blacksheep.org; Thu, 03 Nov 2005 17:23:07 +0000 Received: from localhost (localhost [127.0.0.1]) by nibbel.kulnet.kuleuven.ac.be (Postfix) with ESMTP id ABE7C4C474 for ; Thu, 3 Nov 2005 17:33:11 +0100 (CET) Received: from smtp01.kuleuven.be (octavianus.kulnet.kuleuven.ac.be [134.58.240.71]) by nibbel.kulnet.kuleuven.ac.be (Postfix) with ESMTP id F3CD84C4CC for ; Thu, 3 Nov 2005 17:33:10 +0100 (CET) Received: from smtp01.kuleuven.be (localhost.localdomain [127.0.0.1]) by smtp01.kuleuven.be (Postfix) with ESMTP id D1FFF63D82; Thu, 3 Nov 2005 17:33:10 +0100 (CET) Received: from dell-rik.fys.kuleuven.be (pc-10-33-165-177.fys.kuleuven.ac.be [10.33.165.177]) by smtp01.kuleuven.be (Postfix) with ESMTP id 7968763D7C for ; Thu, 3 Nov 2005 17:33:10 +0100 (CET) Message-Id: <5.1.0.14.0.20051103173148.0307fea8@u0019445.kuleuven.be> X-Sender: u0019445@u0019445.kuleuven.be X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Thu, 03 Nov 2005 17:37:20 +0100 To: rsgb_lf_group@blacksheep.org From: Rik Strobbe In-Reply-To: References: <000901c5e005$e2d511c0$fe79a8c0@PCVONWALTER> Mime-Version: 1.0 X-Virus-Scanned: by KULeuven Antivirus Cluster Subject: Re: LF: low pass filter for power use Content-Type: text/html; charset=windows-1252 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-PN-SpamFiltered: by PlusNet MXCore (v2.00) Content-transfer-encoding: 8bit Hello Tom,

I believe the first one is the "G3YXM filter".
The pitfalls when using a 147 kHz filter might be:
- higher attenuation at 137 kHz
- more sensitive to changes of the antenna impedance (if the antenna is not 50 Ohm then it will affect the filter, largest changes are at frequencies close to the "filter slope").

73, Rik ON7YD

At 17:21 3/11/2005 +0100, you wrote:

Hi Lf's
in all circuit diagrams I find filters like 12nF---->54uH---->27nF----->54uH----->12nF
here is the 3db point at 250khz.
Has anyone test a filter in this configuration 47nF-----> 54uH----->82nF------54uH----->47nF
here is the 3db point at 147khz.
The 2. filter gives a better suppress of the harmonics!
Wat is the reason that all use the fist one?

best 73' Tom DL4EAU


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