[Elecraft] K2 Filter question

[Michael Babineau]

It is also worth mentioning that the KAF2 (audio filter and real-time clock) is  a good addition for CW reception.

IMHO it does help a lot when copying weak signals and also having the real-time clock is useful. 

http://www.elecraft.com/kaf2.htm

Michael VE3WMB (K2 #5995) 


>From: Don Wilhelm <donwilh at embarqmail.com <mailto:donwilh at embarqmail.com>>
>Subject: Re: [Elecraft] K2 Filter question
>Date: January 8, 2017 at 11:45:09 AM GMT-5
>To: Mike Smith VE9AA <ve9aa at nbnet.nb.ca <mailto:ve9aa at nbnet.nb.ca>>, Elecraft at mailman.qth.net <mailto:Elecraft at mailman.qth.net>
>Reply-To: donwilh at embarqmail.com <mailto:donwilh at embarqmail.com>


>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