[Elecraft] K3 15khz 2nd IF?

[Brett gazdzinski]

Just wondering if anyone can clue me in on the 15 KHz second
IF frequency used on the K3.
I was wondering why 15KHz, instead of 10, or 50 KHz?

I know it gets harder to sample the higher you go, but what are the 
advantages of 15 KHz over audio frequencies, and is not 20 or 50 KHz
possible? What about 10KHz?

Just what drives the choice of 15 KHz?

Brett
N2DTS