[Elecraft] Elmer Question - psk31 and the K2

[Don Wilhelm]

Tom,
In my experience, the sound card would not be damaged - a normal soundcard
output can be either shorted or run open circuit and cause no damage to
itself - the shorted condition will cause the most current to flow and an
open circuit would cause the highest voltages (assuming a low impedance
output stage - which is a strong liklihood).

Now, overdriving the K2 microphone input can cause much distortion and if
the voltage levels were sufficiently high, it may be possible to saturate
the audio input transistor - and that possibly could cause damage to the
following audio stages - although I think it is quite unlikely for circuits
created using good design practice.

Whether damage is possible or not is design dependent, and specifically for
the K2, it depends on the design inside the SSM2165 IC (U3).  In any case,
some type of voltage divider is required to cut the level at the soundcard
speaker/line-out signal down to a size that is normal for a microphone
input.

73,
Don W3FPR

----- Original Message -----
>
>     "The reason for the resistors is a 100 to 1 or better voltage divider
is
> required so the sound card from your computer does not get overloaded and
> damaged"  This is the part I don't follow.  If I'm following this
correctly.
> I am taking the audio OUTPUT (the speaker connection) of the computer's
> sound card and feeding it to the K2's microphone input, so the data can be
> transmitted.  If this is true, how could the sound card get damaged?
Isn't
> the cable carrying the  audio "out of" the computer?
>
>     In all likelihood I am missing something, as guys like Glen certainly
> know a lot more about these things than I do.  If someone could set me
> straight, I'd appreciate the help.
>
> Also, of course, I read Glens write up AFTER I had already tried running
my
> software (Digipan, BTW), so who knows what my sound card looks like (But I
> am still driving the rig, at least according to the RF indicator).
>
> Thanks for any help you may offer,
>