[Elecraft] KAF2 or KDSP2 for K2?

[Bill W4ZV]

John Huggins, kx4o wrote
> 
> One question I have about the choice between the KAF2 and KDSP2 is what 
> about having neither.
> 
> How would one describe the receiver/filter capabilities of the bare K2?
> 

John neither is a valid response for some situations...it all depends on
your operating modes.  I use my QRP K2 exclusively for field operating so
take my comments with that in mind.  I used the rig for several years with
no filtering besides the XFIL (set for 1000/700/400/100 BWs).  I then
decided to add a KAF2 thinking it might add some capability, but in fact I
seldom use it.  I even modified the AF2 setting for low ringing per KI6WX's
analysis (BTW the KI6WX link on LA3ZA's mod site no longer works).

This past weekend in the QRPTTF event, conditions were such that nearly all
QRP signals were at or below the very low noise floor.  Very few signals
would light ANY meter bars even with the preamp on.  I found my best copy
was using the 1000 Hz BW and no AF filtering.  I tried both the KAF2's AF1
and AF2 settings several times but always returned it to off for best copy.  

For copying weak signals in white noise, I find my ears usually beat any DSP
(e.g. K3) or analog filtering with the sole exception of the K3's APF, which
can help in some situations.  My ears need wide bandwidth to help
discriminate weak signals from noise and the fact that APF allows this (a
very sharp AF filter with gain superposed on a much wider IF bandwidth)
makes it helpful in certain situations.

Anyway, the K2 without additional AF filtering works well for me when
copying weak signals if that's your primary operating mode.  I did
rediscover this weekend how much I hate (i.e. worse than dislike!) the very
high distortion in the K2's sidetone which makes it difficult to match
signals when zero-beating.  TF3MA's mod for that is next on my K2 list:

http://www.raunvis.hi.is/~matti/TF3MA/sidetone_tf3ma.html

73,  Bill  W4ZV 




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