LF: Re: Sound Card mic Impedance

["Clemens Paul" <cpaul@gmx.net>]

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