Return-Path: Received: from mtain-ma05.r1000.mx.aol.com (mtain-ma05.r1000.mx.aol.com [172.29.96.13]) by air-mb02.mail.aol.com (v129.4) with ESMTP id MAILINMB023-a1914d0a8514133; Thu, 16 Dec 2010 16:31:00 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-ma05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 539B7380000FC; Thu, 16 Dec 2010 16:30:58 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PTLOR-0001Nt-H3 for rs_out_1@blacksheep.org; Thu, 16 Dec 2010 21:29:43 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PTLOQ-0001Nk-UE for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 21:29:42 +0000 Received: from mailout-de.gmx.net ([213.165.64.23] helo=mail.gmx.net) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1PTLOO-0008Ei-8h for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 21:29:42 +0000 Received: (qmail invoked by alias); 16 Dec 2010 21:29:33 -0000 Received: from p5DC4308C.dip.t-dialin.net (EHLO Clemens04) [93.196.48.140] by mail.gmx.net (mp065) with SMTP; 16 Dec 2010 22:29:33 +0100 X-Authenticated: #17214767 X-Provags-ID: V01U2FsdGVkX183gaoRgM03KVwm7QmzxXSyru+p0Phoj9Jhfyqttc Vb3cF1JIUL8nbw Message-ID: <00b901cb9d68$551bdc80$0201a8c0@Clemens04> From: "Clemens Paul" To: References: <005201cb9d61$8bdf3200$0201a8c0@Clemens04> <061B7DFBCF9048E9A7F715A530E1EE96@lindavideo> Date: Thu, 16 Dec 2010 22:29:25 +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: Re: Re: Sound Card mic Impedance Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B5_01CB9D70.B1C421B0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_40_50,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: 3039ac1d600d4d0a85114a35 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_00B5_01CB9D70.B1C421B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit The 50-Ohm-termination at the output of the LP filter represents a 50-Ohm-*source* which is looking into the input impedance of the soundcard. Hence the gross (power-)mismatch (SWR 80). For such high impedances at vlf (=audio) frequencies voltage matching would be much more efficient. 73 Clemens DL4RAJ ----- Original Message ----- From: Ken To: rsgb_lf_group@blacksheep.org Sent: Thursday, December 16, 2010 10:04 PM Subject: LF: Re: Re: Sound Card mic Impedance Hi Clements. Are you sure, shunting a 50 ohm resistor with 4k ohms reduces it down to 49.38 ohms or am I missing something?. 73. Ken M0KHW ----- Original Message ----- From: Clemens Paul To: rsgb_lf_group@blacksheep.org Sent: Thursday, December 16, 2010 8:40 PM Subject: LF: Re: Sound Card mic Impedance 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_00B5_01CB9D70.B1C421B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
The 50-Ohm-termination at the output= of the LP=20 filter represents a
50-Ohm-*source*=20 which is looking into the input impedance of the soundcard.
Hence the gross (power-)mismatch (SWR= =20 80).
For such high impedances at vlf= =20 (=3Daudio) frequencies
voltage matching would be much= more=20 efficient.
 
73
Clemens
DL4RAJ
 
 
----- Original Message -----
From:=20 Ken
Sent: Thursday, December 16,= 2010 10:04=20 PM
Subject: LF: Re: Re: Sound Ca= rd mic=20 Impedance

Hi Clements.
Are you sure, shunting a 50 ohm res= istor with 4k=20 ohms reduces it down to 49.38 ohms or am I missing something?.
73.
Ken
M0KHW 
----- Original Message -----
From:=20 Clemens Pau= l
Sent: Thursday, December 16= , 2010 8:40=20 PM
Subject: LF: Re: Sound Card= mic=20 Impedance

Ken,
 
>I am doing  a Low Pass= Filter to use=20 with Winrad, F1, 20kHz, F2, 30 kHz, 100kHz -80 dB (theoretical)&nb= sp;with a=20 >characteristic impedance of 50 ohms, with this high input=20 impedance I can locate the filter very close to the soun= d >card=20 mic input and terminate the filter output with a 50 ohm=20 resistor.
 
Assuming 4kOhm input impedance of= the soundcard=20 this will cause a mismatch loss
of around 13dB (95% loss) which= may or=20 may not cause concern depending of the signal=20 level of
your antenna.
 
 
73
Clemens
DL4RAJ
----- Original Message -----
From:=20 Ken
Sent: Thursday, December= 16, 2010=20 9:06 PM
Subject: LF: Sound Card= mic=20 Impedance

Thank you all LFs.
Thank you for all the info that= you sent me,=20 it looks they can be anything from 4k ohms upwards, this is ok= for me, I=20 am doing  a Low Pass Filter to use with Winrad, F1, 20kHz,= F2, 30=20 kHz, 100kHz -80 dB (theoretical) with a characteristic impe= dance of=20 50 ohms, with this high input impedance I can locate= the filter=20 very close to the sound card mic input and terminate the filter= output=20 with a 50 ohm resistor. Hopefully this will eliminate the= BC intermod=20 I was experiencing when trying to receive Chris G3XIZ the other= =20 day.
 
73
Ken
M0KHW  =20 I091TV 
------=_NextPart_000_00B5_01CB9D70.B1C421B0--