Return-Path: Received: from mtain-dc09.r1000.mx.aol.com (mtain-dc09.r1000.mx.aol.com [172.29.64.137]) by air-db06.mail.aol.com (v129.4) with ESMTP id MAILINDB061-85f24d0a799c2e0; Thu, 16 Dec 2010 15:42:04 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dc09.r1000.mx.aol.com (Internet Inbound) with ESMTP id 12631380001DE; Thu, 16 Dec 2010 15:42:02 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PTKdQ-0000M9-Eo for rs_out_1@blacksheep.org; Thu, 16 Dec 2010 20:41:08 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PTKdP-0000M0-U9 for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 20:41:07 +0000 Received: from mailout-de.gmx.net ([213.165.64.22] helo=mail.gmx.net) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1PTKdN-0007jW-77 for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 20:41:07 +0000 Received: (qmail invoked by alias); 16 Dec 2010 20:40:59 -0000 Received: from p5DC4308C.dip.t-dialin.net (EHLO Clemens04) [93.196.48.140] by mail.gmx.net (mp018) with SMTP; 16 Dec 2010 21:40:59 +0100 X-Authenticated: #17214767 X-Provags-ID: V01U2FsdGVkX1/5+R5dNsn5kUbcOfcmBoNe6xZUZkZn6auo9krl57 L/fPahLFZ71fwE Message-ID: <005201cb9d61$8bdf3200$0201a8c0@Clemens04> From: "Clemens Paul" To: References: Date: Thu, 16 Dec 2010 21:40:55 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3664 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3664 X-Y-GMX-Trusted: 0 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: Sound Card mic Impedance Content-Type: multipart/alternative; boundary="----=_NextPart_000_004E_01CB9D69.EB3754F0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,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-sid: 3039ac1d40894d0a799a7fe8 X-AOL-IP: 195.171.43.25 ------=_NextPart_000_004E_01CB9D69.EB3754F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Ken, >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. Assuming 4kOhm input impedance of the soundcard this will cause a mismatch loss of around 13dB (95% loss) which may or may not cause concern depending of the signal level of your antenna. 73 Clemens DL4RAJ ----- Original Message ----- From: Ken To: rsgb_lf_group@blacksheep.org Sent: Thursday, December 16, 2010 9:06 PM Subject: LF: Sound Card mic Impedance 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 when trying to receive Chris G3XIZ the other day. 73 Ken M0KHW I091TV ------=_NextPart_000_004E_01CB9D69.EB3754F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ken,
 
>I am doing  a Low Pass Filte= r to use with=20 Winrad, F1, 20kHz, F2, 30 kHz, 100kHz -80 dB (theoretical) with= a=20 >characteristic impedance of 50 ohms, with this high input impedanc= e I=20 can locate the filter very close to the sound >card mic input= and=20 terminate the filter output with a 50 ohm resistor.
 
Assuming 4kOhm input impedance of the= soundcard=20 this will cause a mismatch loss
of around 13dB (95% loss) which may= or may not=20 cause concern depending of the signal level of
your antenna.
 
 
73
Clemens
DL4RAJ
----- Original Message -----
From:=20 Ken
Sent: Thursday, December 16,= 2010 9:06=20 PM
Subject: LF: Sound Card mic= =20 Impedance

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 ver= y close to=20 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 
------=_NextPart_000_004E_01CB9D69.EB3754F0--