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Hello Andy.
I must admit I had not thought of that, so used to
using equal impedances, 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
almost standard values, 330000 nf, 470uh, which I concluded would make life
easier.
73s
Ken
M0KHW
----- Original Message -----
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
trying.
AADE filter designer lets you have different termination
impedances.
Andy
On 16 December 2010 20:06, Ken <[email protected]>
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 when trying to receive Chris G3XIZ the other day.
73
Ken
M0KHW
I091TV
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