[Elecraft] K2 filter attenuation

[Eric Swartz WA6HHQ - Elecraft]

Hi Rich,

When you say 'narrowest filter', what bandwidth are you referring to? Is it
below 400 Hz to 500 Hz?

The K2 was designed for a proper impedance match to the CW crystal filters
when they are adjusted in a range between 400 and 800 Hz wide. Narrower
filter settings are not guaranteed and are going to vary from rig to rig.
Wider settings will have an increase in ripple in their passband. (That's
why we supply an additional SSB fixed width filter in the KSB2.) We have
seen good results on most K2s down to 300 Hz. I guess we shouldn't be
surprised that some builders will try and push the envelope even further :*)

Settings below 400 Hz are outside the main K2 design parameters and
certainly will have more attenuation in their passbands. In most cases
though, since the noise figure of the RX is set by the front end of the
receiver (pre-amp, mixer and post amp) this will not directly impact
sensitivity. It will reduce overall RX gain though.

73, Eric  WA6HHQ



Rich Lentz wrote:
> 
> Back to the original subject -
> 
> I also hear and see (with spectrogram) a noticeable drop in signal (in
> excess of 10 db) on the narrowest filter.