[Elecraft] [K2] KSB2 Filter alignment question

[Don Wilhelm]

Gareth and all,

Yes, Spectrogram (or other audio spectrum analyzer) is *the* way to set 
up the K2 filters with ease.

A slight variation on the N0SS plots, which were done with the original 
2.1 kHz OP1 filter is to alter the position of the 2.4 kHz width OP1 
filter slightly.
Set markers at 300 Hz and 2600 Hz and move the BFO to position the 
passband between those two markers.

If you align it that way, you will have a suitable filter in FL1 for 
both transmit and receive.  In other words, there is no need to also set 
FL2 to the OP1 filter.

I have aligned many SSB filter sets that way for my customers and have 
never heard a complaint.
I adjust the other 3 filters to be progressively 200 Hz more narrow than 
the prior filter (using Spectrogram to measure the actual width of the 
filter).  I normally adjust FL2 to a measured 2.2 kHz width, FL3 to 2.0 
and FL3 to 1.8 kHz.  On many K2s, the actual filter width is greater 
than width shown on the display.  The low frequency -6dB passband corner 
of the FL2 filter is set at 350 Hz, FL3 at 400 Hz and FL4 at 450 Hz.  
The low frequency end of the passband cannot be cut very much without 
loosing intelligibility, but the high end can be cut considerably to 
eliminate QRM while retaining intelligibility.

73,
Don W3FPR

On 9/2/2014 8:13 AM, Gareth - M5KVK wrote:
> K2 serial 03885 fitted with KSB Rev C board.
>
> When I installed the KSB2 board recently, I went through the process of
> setting up the BFOs as per the KSB2 manual. However, I just downloaded
> Spectrogram and went through N0SS's procedure for setting up the filters.
>
> Most of the adjusted settings were within 2-300Hz of those in the manual
> (all on the higher side), but a couple were moved quite a bit. I'm
> interested in others' experiences in this area.
>
> The outliers were USB FL2 which needed to be 500Hz higher and USB FL3 which
> needed to be 700Hz higher.
>
> The main issue when looking with Spectrogram was that the USB spectrum was
> far too bassy when the BFOs were set as per the manual.
>
> Regards
>
>