Modifications to the Elecraft K2 that took place for various serial numbers prior to 3000

Part 3 of LA3ZA Unofficial Guide to Elecraft K2 Modifications

Basic K2: Improved Performance
Reference	Description	Comment	Complexity	K2 Status	Source
Changed turns ratio on T7 on RF board	Changed from 11:3 to 20:5 from rev B to rev C manual.	Changes termination of X-tal filter for more gain esp. at low bandwidths		In Rev C manual (19 April 2000).	Elecraft
Reduced no of turns on T3 (RF board)	Changed from 10 turns bifilar to 5	Better efficiency of PA		In Rev C manual	W6EMD
R18/19 in audio mute circuit (ctrl board) replaced by jumpers	Short out two resistors	More audio gain		All K2s after May 1999	Elecraft
¤Frequency shift on transmit due to walking VFO	Caused by cycling of power for optical encoder combined with a position close to the border between counts.	Important, but only required for firmware prior to 2.02E.	Simple, just an installation of a strap.	Recommended for firmware prior to 2.02E. Fixed in all K2s with serial numbers 2696 and above.	Elecraft
×More accurate current metering	Some RF gets into current sense circuit on 160/80 m	Simple to do (control board)	Make C42 0.1 µF (100 nF)	Included with K2s with S/N 2856 and higher	Elecraft
RF Detector Improvement	More accurate indication of RF output at higher frequencies		Replace a diode and a resistor	In all K2s some time before Aug. 2001	Elecraft
Improved current measurement accuracy	Change control board R7 from 1.96k to 1.78k	Step "10. Misc. Control Board Changes" in A to B upgrade instructions.		In all K2s some time before Aug. 2001	Elecraft
SSB Option KSB2
Increased ALC delay time	Improve intermodulation distortion in PSK31 transmission	Important improvement of PSK31 performance with no side effect on SSB performance	Change 3 resistors and a capacitor	Changed in all KSB2 kits shipped after Sept 5, 2001. Mod kit KSB2MDKT Updated April 2014	KI6WX

Items marked with × are implemented in my K2, while ¤ denotes modifications that I have tried, and then removed.

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First version 8 Nov 2001, last update 9 April 2014.

73, Sverre Holm, LA3ZA