Mike,
The K2 has a built-in 5 pole filter on the RF board that you can set to
variable widths using the CAL FIL menu - you must have the internal
counter probe to change the filter settings.
There are 4 filter settings for each mode.
These are not "roofing filters" as used in the K3, but IF crystal
filters. The filter type in the base K2 is of a Cohn design and the
width can be changed as I stated above. Its design width is about 500Hz
and gives a nice passband from about 1.5kHz down to about 200Hz.
It can be widened out to SSB listening levels, but the passband becomes
quite ragged at those wider widths. It is however suitable for SSB
listening. The filter on the KSB2 option board has a nice flat passband.
The KSB2 option (for SSB) has a fixed width 7 pole filter. The early
filters were 2.1kHz width, but more recent filters are 2.4kHz.
Elecraft has a capacitor kit which will allow you to change the filter
width.
The crystals used in the K2 filter were upgraded to better speced
crystals at SN 2560. I would recommend that K2s below that SN be
upgraded with the new crystals. Elecraft sells a kit of matched
crystals at a very reasonable price a set of 7 for the base K2 or a set
of 14 for both the base K2 and the KSB2 option.
73,
Don W3FPR
On 1/8/2017 11:10 AM, Mike Smith VE9AA wrote:
It's Mike, VE9AA...I own a K3 but almost never use it (only for FD and
portable ops -I've used it twice in my year of ownership)
I am thinking about maybe buying a used K2/10 with many options,(no DSP
board I don't think) but as I don't know a thing about the K2 (and after
reviewing the Elecraft website) I had this hopefully simple question. (I
have not yet contacted the seller)
Are there optional CW filters still available for the K2 or does it come
with them all built in ?
I do mostly CW so was looking at doing most of my operating with a 200-300Hz
filter.(and perhaps with a 1.8kHz SSB filter when I am on phone)
I apologize if the answer is overly obvious !
Thanks much,
dit dit Mike VE9AA
Mike, Coreen & Corey
Keswick Ridge, NB
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