[Elecraft] 1.8 or 2.1 kc Filter

[Ed Muns]

> Anyone have experience with 1.8 and 2.1 kc filters for the K3?
> Trying to decide which one to get..
> 
> I am a DXer exclusively......not a contester...
> work CW rarely....
> 
> 
> Does the audio from 1.8 sound too pinched....? 
> I just dont want to hear a 59+10 signal that is 3 kc..from 
> the frequency I am listening on....
> 
> any thoughts? on what filters to get..

Don't commit to any optional filters until you actually use your K3 and
determine what bandwidths work best for your preferred operating scenarios.
The stock 2.7 kHz filter provides excellent roofing filter protection for
the DSP which is where you set your receive bandwidth.  Try different SSB
receive bandwidths and see what you like.  I almost always use 1.6 kHz for
SSB and do not find it at all "tinny" or "too narrow" in the K3 as some
other replies are indicating.  In most other radios, 1.6 kHz far too narrow,
at least for me to copy easily.  The K3, however, sounds beautiful at these
narrow bandwidths.  Don't make a K3 crystal filter decision based on
experience with other radios, especially someone else's experience with
other radios!

The easiest way to narrow the bandwidth on SSB is to reduce HI CUT.  Until
you reach a bandwidth of about 1.5 kHz, you don't need to adjust LO CUT or
anything else.  This reduces bandwidth while moving Fc down with it.
Effectively, adjusting only HI CUT simultaneously adjusts WIDTH and SHIFT
ideally for SSB.  This is far easier than adjusting WIDTH, then SHIFT to get
the sound right.  You can slide between 2.0 and 2.7 kHz to see how narrow
you can go for the sound you want.  So, assuming you have the stock 2.7 kHz
crystal filter, and have told the K3 it is 2.7 kHz wide, start there and
reduce HI CUT from 2.7 kHz to 2 kHz.  LO CUT will remain at 200 Hz and you
will end up at a bandwidth of 1.8 kHz.  I think you will find that it sounds
fine.  I prefer these narrow bandwidths because they take out the highs
between 2 and 3 kHz.  I think this is more intelligible (in the K3) for
communications.  So-called "hi-fidelity" is something else.

Once you get a feel for the narrow SSB receive bandwidth you like, then
select a crystal filter that is outside that bandwidth, if you are worried
about strong nearby signals interfering with the DSP's ability to provide
the listening bandwidth you want.  The Elecraft/INRAD 1.8 kHz crystal filter
is actually about 1.9 kHz at the -6 dB points, so it won't affect your DSP
bandwidths much at 1.7 kHz or below.  If that's too narrow for you, then
consider the 2.1 which will allow you to get to 2.0 kHz or lower since it is
actually about 2.2 kHz.

73,
Ed - W0YK