----- Original Message -----
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 -----
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
