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  1. This is about the third version of a home brew interface to use PC headset on the 857D. The first i built, I cannot find the site for but it used a 470Uf electrolytic (parallel with mic) and 47Uf electrolytic (series with a 1K resistor in the mic + circuit) as filtering. It as well as the 2nd version use 4.7K ohm as current limiting resistors (in the +5 vdc ckt) where you use the 2.2K and both use .01Uf as isolation caps where you use the 10Uf electrolytic.

    I have used the first with a bit of success and it seems to provide a pretty nice audio that I found has a broader range than the oem mic. I have built the second to use in my car but have not used it so do not know how much the electrolytic caps and 1K resistor do as far as tuning the audio response.

    Does yours get any better audio reports than the oem hand mic or is it more tinny without any filtering as the PC headsets tend to do without some massaging?

    Yours is definately more simple than either of the interface circuits I have built so I may try it in a bit and do some on the air comparisons.

    Thanks for the info… – ac0hd


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