[Elecraft] CW/SSB K2 Filter Flexibility

[Don Wilhelm]

Michael,

Congratulations on your decision to purchase the K2 - you will not be
disappointed IMHO.

The K2 has a total of 12 filter 'slots' (8 if the RTTY mode is not
activated).
Each mode allows 4 bandwidth selections - and you can set the BFO
frequencies independently for each side of each filter (LSB/USB or CW/CWrev
or RTTY/RTTYrev).  Either the fixed bandwidth OP1 filter or any bandwidth of
the varaible filter can be selected.  There is only one caution - for SSB
transmit, the K2 uses the FL1 settings, so these must be set for the best
transmitted signal - all other selections are for receive only and you can
set them to please your ears without impacting the transmit signal.

The filter in the base K2 is a variable bandwidth filter which was designed
for optimal performance for CW (narrow bandwidths) and while it is usable at
wider bandwidths, I have not been very satisfied with bandwidths greater
than about 1600 Hz due to the increased passband ripple and the slope of the
high frequency side.

It is a VERY GOOD filter for CW - but for SSB this filter has some
shortcomings.

The 2.2 kHz OP1 filter that comes with the SSB option has a quite decent
shape for SSB - so with both filters installed, you have quite a range of
selections for the K2 filters.

73,
Don W3FPR

----- Original Message -----
...
>   But, it appears the situation changes when one adds the SSB adapter
(which
> I plan to do). Table 3 on page 20 of the KSB2 manual rev C shows a similar
> table for a K2 with the SSB adapter. I assume OP1 refers to the 7-pole
> fixed-width crystal filter that is on the SSB adapter that has a width of
> 2.2kHz?
>
>   Given the above and the suggested arrangement in table 3, it appears
that
> FL1 will provide 2.2kHz for both CW and SSB and FL2 will also provide
2.2kHz
> for SSB. Would it be possible to use the CW filter for SSB's FL2 instead
of
> OP1 in order to obtain a 2.0kHz bandwidth for the SSB FL2 setting? If so,
> since this isn't the suggested filter setting, I assume there must be some
> sort of downside to such a configuration?
>
 ...