[TenTec] Argonaut II internal CW audio filter?

[Steve Berg]

I am looking for a way to either disable the internal audio low pass CW 
filter in my Argonaut II, or else raise its cutoff frequency quite a 
bit.  I believe that presently it has a cutoff at 1 KHz, and that makes 
it difficult to copy auroral CW signals which sound like someone hissing 
in Morse.  I use the old radio as the tunable IF rig with my VHF 
transverters.

73,

Steve WA9JML