Hi Phil, I am exclusively a QRP CW guy. I put the KAF2 audio filter in my K2. It works great but I have only used it a couple of times. (I've had it for about 7 or 8 months.) The regular audio filter settings on the stock radio do a very good job for casual operating. The K2 is a lot of fun to build and operate. You will enjoy it. 73, Paul - N8XMS