[Elecraft] KAF2 function and more!

[Floyd Sense]

As everyone who has the KAF2 knows, it works pretty well and I've read
several posts here indicating some folks have missed it after installing the
DSP unit.  If you don't mind having another small box sitting on the
operating desk, here's a way to have KAF2-like function and more for your K2
at reasonable cost.

I use an old Autek Research QF-1A SSB/CW/AM filter unit, feeding it with the
speaker output from the K2 (headphone output OK as well).  In peaking mode,
it sounds like the KAF2, but the selectivity is continuously variable from
very, very broad to extremely narrow.  The frequency of the peak is
adjustable from the front panel.  There's a notch function that can be used
along with the peak function, and highpass and lowpass capabilities for
tailoring response for SSB or just knocking down the hiss on CW.  It has
enough output to drive a speaker directly.  The built-in power supply can
introduce a bit of low level hum depending upon the impedance of your
headphones.  I modified the QF-1A by disconnecting the AC cord and lifting
the anodes of the full-wave rectifier diodes.  13.8 VDC from the station
power supply is then fed to the diodes, resulting in a completely hum-free
filter.

The QF-1A is about the age of some of the younger K2 owners, and can often
be found on eBay or elsewhere for $20-$40.

73, Floyd - K8AC