Return-Path: Received: from mtain-de10.r1000.mx.aol.com (mtain-de10.r1000.mx.aol.com [172.29.64.210]) by air-db07.mail.aol.com (v129.4) with ESMTP id MAILINDB072-86214d0a7da13a; Thu, 16 Dec 2010 15:59:13 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-de10.r1000.mx.aol.com (Internet Inbound) with ESMTP id 1978138000145; Thu, 16 Dec 2010 15:59:10 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PTKuH-0000fa-O4 for rs_out_1@blacksheep.org; Thu, 16 Dec 2010 20:58:33 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PTKuH-0000fR-7l for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 20:58:33 +0000 Received: from nm16-vm0.bullet.mail.ne1.yahoo.com ([98.138.91.49]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1PTKuF-0007tO-QW for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 20:58:33 +0000 Received: from [98.138.90.53] by nm16.bullet.mail.ne1.yahoo.com with NNFMP; 16 Dec 2010 20:58:24 -0000 Received: from [98.138.89.254] by tm6.bullet.mail.ne1.yahoo.com with NNFMP; 16 Dec 2010 20:58:24 -0000 Received: from [127.0.0.1] by omp1046.mail.ne1.yahoo.com with NNFMP; 16 Dec 2010 20:58:24 -0000 X-Yahoo-Newman-Id: 824474.91742.bm@omp1046.mail.ne1.yahoo.com Received: (qmail 1553 invoked from network); 16 Dec 2010 20:58:24 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btinternet.com; h=DKIM-Signature:Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=uOWeKtnHm/k7MLJ0Pfnk40pStrAg9g6PBaKVHcTOb59wNIcH1OCo0iq2bYXpuysyxtXosBZ2Yfo8U/WmVfuhJJv1+k3pvYYPGi1CidYXgDuOsEslMB3qO22qd4iqQ8X+wJa08/uHD0HcESIyRED4RQT5eKPfJmC9KagwN7VWTqI= ; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=s1024; t=1292533104; bh=OyZ4LHYxCj2dFDfhIsLWvtmXl35xaqMVnu2BnIKtvx0=; h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=ajrds6EVdCvXgNrR9P6yNsF/U25DVn/WOxPT/IQIe6GuhpYkhutOzCXhdNo6Ik6P3ddzMmrQJMMK/mUkg0MpMr6WNzUutaIj8LqMmwf56G6dS3AiBUsMpx3CKm0jchATbpOHCDfNLfl3H+dbqSGxE3ehsb53AFmZnODPC6pbo0U= Received: from lindavideo (ken.h.wright@86.162.64.127 with login) by smtp145.mail.mud.yahoo.com with SMTP; 16 Dec 2010 12:58:24 -0800 PST X-Yahoo-SMTP: 9Y6mUHuswBAgnrOsukIiNdFDf95uy_Dz34nY1hlg2liKgYD952sjbg-- X-YMail-OSG: d_BB7gQVM1m7y8_.mJjaA0mpU9f8UN06y3DV93l6_tPIU0k KKNREd6bxM_VlCrB4BQbB2K.ZOCTW8BBbcrVQox9p0QyPWni9ZcUsA7itEs5 C17vGRwS1E7H4lJjOZfnpkPRxDKgdvYc7uwore3pRni.6zmGJAQXrVNmLZn2 UeAT2YI8orcu2qNLmPRwLR80g6yHttD6AvyFLthRLo6S_4TXVArvLeh0Mwbp 5rAloJfGXunJIi5dSEX7jRHqmzmnViOW3R9kCdjGhqW6tks1PYSGJHv8MmtK FE1xAYVxfT4oybOW7Lq7yxXlb1DgvPZcWneHxCopBqFT_YUyU..MEAqcCH7c ZHB5aaJ5XWtMFuh4x2OOBqJFnqHjBZl2jik1AbQp.7nI- X-Yahoo-Newman-Property: ymail-3 Message-ID: From: "Ken" To: References: Date: Thu, 16 Dec 2010 20:58:21 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 DomainKey-Status: good (testing) X-Spam-Score: 3.4 (+++) X-Spam-Report: autolearn=disabled,FORGED_MUA_OUTLOOK=3.36,HTML_MESSAGE=0.001,UNPARSEABLE_RELAY=0.001 Subject: Re: LF: Sound Card mic Impedance Content-Type: multipart/alternative; boundary="----=_NextPart_000_005B_01CB9D63.F9127290" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.5 required=5.0 tests=FORGED_MUA_OUTLOOK,HTML_30_40, HTML_FONTCOLOR_UNSAFE,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-d255.2 ; domain : btinternet.com DKIM : pass x-aol-sid: 3039ac1d40d24d0a7d9e49a4 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_005B_01CB9D63.F9127290 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Andy. I must admit I had not thought of that, so used to using equal impedan= ces, I did use AADE for this and the component values came almost as= standard values, I used the tolerance option of 20% and they were alm= ost standard values, 330000 nf, 470uh, which I concluded would make li= fe easier. 73s Ken M0KHW=20 ----- Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, December 16, 2010 8:25 PM Subject: Re: LF: Sound Card mic Impedance If its a passive L/C filter, why not do a version with unequal Zin= and Zout and take advantage of the voltage gain in going from 50ohms= to, say, 500 ohms? That will give you an apparant 10dB without tryi= ng. AADE filter designer lets you have different termination impedances. Andy www.g4jnt.com =20 On 16 December 2010 20:06, Ken wrote: Thank you all LFs. Thank you for all the info that you sent me, it looks they can be= anything from 4k ohms upwards, this is ok for me, I am doing a Low= Pass Filter to use with Winrad, F1, 20kHz, F2, 30 kHz, 100kHz -80 dB= (theoretical) with a characteristic impedance of 50 ohms, with this= high input impedance I can locate the filter very close to the sound= card mic input and terminate the filter output with a 50 ohm resistor= . Hopefully this will eliminate the BC intermod I was experiencing whe= n trying to receive Chris G3XIZ the other day. 73 Ken M0KHW I091TV=20 ------=_NextPart_000_005B_01CB9D63.F9127290 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Andy.
I must admit I had not thought of tha= t, so used to=20 using equal impedances, I did use AADE for this and the component= values=20 came almost as standard values, I used the tolerance option of 20% and= they were=20 almost standard values, 330000 nf, 470uh, which I concluded would make= life=20 easier.
 
73s
Ken
M0KHW 
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Thursday, December 16,= 2010 8:25=20 PM
Subject: Re: LF: Sound Card= mic=20 Impedance

If its a passive L/C filter, why not do a version with une= qual Zin=20 and Zout and take advantage of the voltage gain in going from 50ohms= to, say,=20 500 ohms?   That will give you an apparant 10dB without=20 trying.
 
AADE filter designer lets you have different termination=20 impedances.
 
Andy
 


 
On 16 December 2010 20:06, Ken <ken.h.wrigh= t@btinternet.com>=20 wrote:
Thank you all LFs.
Thank you for all the info that= you sent me, it=20 looks they can be anything from 4k ohms upwards, this is ok for me= , I am=20 doing  a Low Pass Filter to use with Winrad, F1, 20kHz, F2,= 30 kHz,=20 100kHz -80 dB (theoretical) with a characteristic impedance= of 50 ohms,=20 with this high input impedance I can locate the filter= very close=20 to the sound card mic input and terminate the filter output with= a 50 ohm=20 resistor. Hopefully this will eliminate the BC intermod I was= =20 experiencing when trying to receive Chris G3XIZ the other day.
 
73
Ken
M0KHW  =20 I091TV 

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