Envelope-to: dave@picks.force9.co.uk Delivery-date: Thu, 03 Nov 2005 21:28:10 +0000 Received: by pih-mxcore09.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1EXmcz-0007tz-JM for dave@picks.force9.co.uk; Thu, 03 Nov 2005 21:28:10 +0000 Received: from post.thorcom.com ([193.82.116.20]) by pih-mxcore09.plus.net with esmtp (PlusNet MXCore v2.00) id 1EXmcz-0007sz-Cd for dave@picks.force9.co.uk; Thu, 03 Nov 2005 21:28:09 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1EXmce-0001fx-UK for rs_out_1@blacksheep.org; Thu, 03 Nov 2005 21:27:48 +0000 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1EXmce-0001fo-CA for rsgb_lf_group@blacksheep.org; Thu, 03 Nov 2005 21:27:48 +0000 Received: from imo-d22.mx.aol.com ([205.188.144.208]) by relay2.thorcom.net with esmtp (Exim 4.51) id 1EXngb-0000Zt-FO for rsgb_lf_group@blacksheep.org; Thu, 03 Nov 2005 22:35:58 +0000 Received: from G0MRF@aol.com by imo-d22.mx.aol.com (mail_out_v38_r6.3.) id l.e2.1fe12226 (17526) for ; Thu, 3 Nov 2005 16:27:36 -0500 (EST) From: G0MRF@aol.com Message-ID: Date: Thu, 3 Nov 2005 16:27:36 EST To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: 9.0 SE for Windows sub 5014 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

In a message dated 03/11/2005 16:23:39 GMT Standard Time, dl4eau@t-online.de writes:

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

Lower insertion loss.

At 1200 Watts every 0.1dB counts. and with a push pull design, the second harmonic should be very low.....it's the odd order harmonics you need to worry about.

Regards

David