Elecraft SSBCAPKT - Manual

Elecraft www.elecraft.com 831-662-8345
Elecraft SSB B/W Modification
(SSBCAPKT)
Installation Instructions
Revision A, November 9, 2004. Copyright © 2004, Elecraft; All Rights Reserved
Parts Inventory
P/N Description QTY
E530016 100 pF, 100V,5%,NPO,0.1LS, CAP 2 EA
E530049 150 pF,100V,5%,NPO,0.2LS, CAP 2 EA
E530141 27 pF, 200V,5%,NPO, 0.1LS, CAP 2 EA
E530144 33 pF, 50V, 5%, NPO, .1LS, CAP 4 EA
E530152 39 pF, 50V, 5%, NPO, .1LS, CAP 6 EA
Introduction
The Crystal Filter Bandwidth Modification capacitor kit provides two options to change the original 2.1 kHz
6 dB bandwidth of the KSB2 SSB filter to either 2.4 kHz or 2.6 kHz. (Note: KSB2s shipped after July 12, 2004
now include the 2.4 kHz bandwidth components.) These modifications are not required for the K2 to function
well in the SSB mode. Instead, they are intended for those who wish to optimize its performance to their personal
preferences.
The 2.4 and 2.6 kHz bandwidth filters also require better matching of crystal motional inductance to minimize
pass-band ripple. We have worked with our supplier to obtain crystals with better control of the motional
inductance. The latest ones now make it possible to increase the SSB filter bandwidth up to 2.6 kHz. The latest
crystals (shipping with all KSB2s since May 2002) are marked with “ECS 4.9136-S” on each crystal. Older
crystals shipped before May 2002 marked with “ECS 4.91-20” or “ECS 4.91-0195” should be replaced when
performing this modification.
The older crystals work fine at a 2.1 kHz bandwidth, but are not optimum for wider bandwidths. If you want to
add a wider SSB bandwidth enhancement to your KSB2, we suggest you order a new set of crystals from Elecraft.
They are Elecraft Part #E850006 (7 matched crystals for the KSB2) or #K2KSB2XTLS (14 crystals for the KSB2
and the K2 CW filters.) See our spare parts order page at http://www.elecraft.com/order_form_parts.htm
Removing parts from the KSB2
The KSB2 is designed with much smaller pad sizes than the other boards in the K2 transceiver. For this reason
it can be more difficult to remove parts without damaging the board. If you don’t have a desoldering tool, cut the
leads off the part and then pull out each piece of wire individually. You will lift pads on the KSB2 if you try to
remove capacitors in one piece. Sacrifice the part and save the board. Crystals may be removed by desoldering
the grounding lead on the top and then wiggling the crystal out by alternately heating each pad on the board.
The best way to remove parts from a KSB2 is to use a Hakko 808 (or equivalent) de-soldering tool. If you are
interested, the Hakko 808 and tips for it are available at http://kiesub.com/hakko808.htm .
Crystal Filter Bandwidth Modification
The KSB2 filter as designed has a 2.1 kHz bandwidth. The response of a crystal ladder filter can be adjusted by
changing the capacitors in the filter. The most critical capacitors are the ones that connect to ground between
each pair of crystals. These capacitors set the coupling between the filter sections. The capacitors in series with a
crystal modify the resonant frequency of each section, but are not nearly as critical in value.