[Elecraft] KAF2 Question....

[Dale M. Boresz]

I have a K2 with the KAF2 filter, and I rarely turn it off, other than 
when I'm using the K2 on SSB which is very rare. The filter is a big 
help in a couple of ways:
 
- When set up properly (so that the center frequency of the filter is 
the same as your BFO frequency - mine is 600 Hz), it creates a slight 
peaking situation which assists one in placing the received signal at 
the same pitch as the BFO frequency. The audible signal level noticeably 
peaks out as you tune it through the filter passband, and if you stop on 
that peak, you'll end up within a few tens of cycles of the BFO frequency.

- The filter also significantly helps to reduce non-signal band noise, 
which in my opinion makes copying much easier on the ears, and much less 
fatiguing.

- The added selectivity of the filter helps a lot in crowded band 
conditions. It's effect is not the same as switching to a tighter xtal 
filter bandwidth; rather, it simply reduces some of the clutter 
surrounding the signal of interest without changing the actual I.F. 
passband.

- You can configure the filter such that both filters are either 
simultaneously on, or both are simultaneously off, OR - so that just the 
first filter can be run, or the combination of the two can be run, or 
they can both be off.  I'd suggest you select the second configuration; 
cascading the two filters is rarely necessary, and creates a bit too 
much peaking for just casual tuning around the bands, although it can be 
helpful in copying very weak signals. It's nice to have the ability to 
use one, both, or neither filter. 

- I have had situations where the station I was trying to copy not only 
was not registering on the S - meter, but was pretty much at the noise 
level. I could hear keying, but couldn't actually copy anything. By 
switching in *both* filters and carefully tuning that station so that it 
lands at the peak of both filters, the station became copyable.

So there you have it - I wouldn't be without the filter. Oh yeah, the 
realtime clock is a nice touch too, but in my opinion it's the filters 
that really provide the bang for the buck.

73, Dale WA8SRA


>
>
> My question is, being the K2 has the VBW filter already, how much more 
> does the KAF2 actually help with CW operation?  I have never operated 
> a rig with the combination of a tight VBW filter and an audio filter 
> of this type, so I do not know what the combination will do for me.  
> The info on the website says it is especially useful on quiet bands, 
> but how does it perform when the bands are quite crowded, i.e. ARRL SS 
> <grin>?
>