[Elecraft] K3 - Filter suggestions for new builder

[Edward R Cole]

I originally chose the 8-pole filters thinking the steeper skirts 
would be useful should I ever take the radio into a dense RF 
environment like it is in the lower-48 states.  MY experience with CW 
indicated 400-Hz was adequate as I could narrow this down with the 
DSP filter.  I chose the 2.8 KHz SSB filter and 13-KHz filter for FM 
use with a VHF transverter.

One note is that changing filters on the main board requires removal 
of the sub-Rx so probably good to figure out what you want from the 
beginning.  I installed a 2.8 and 13 KHz filter in my sub-Rx, 
thinking I could get the full bandwidth in audio to use with 
soundcards for SDR sw.  But I learned that audio is limited to 4-KHz 
regardless of IF filter so I ended up selling the extra 13-KHz filter.

I have thought of adding a 1.8 or 2.1 KHz filter for working tough 
SSB signals.  I do try running the DSP down to that bandwidth but 
find that the DSP audio distortion sometimes is counterproductive to 
hearing weak SSB.  I do not have trouble with dense local QRM up here 
in Alaska.  I wonder if the roofing filters are easier to listen thru 
than the DSP filter?

I did not install a second 400-Hz filter in the sub-Rx and that may 
be an error when I start running dual-pol diversity reception for 
CW-eme.  At present, I only run diversity Rx in USB since I am 
running JT-65 on 2m-eme.  I am testing a new program called MAP65 
which maps and decodes all JT65 signals in a 90-KHz window.  This 
covers 144.090-144.170 digital eme sub-band, nicely.

Someday it would be interesting to set up a crossed dipole on 20, 15 
, or 10m and listen in diversity Rx.  Crossed horizontal dipoles 
actually sample different polarities of refracted HF.  According to 
KL7AJ all HF is converted to circular polarity upon refraction in the 
ionosphere (see the recent article in QST by him).

73, Ed - KL7UW