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





K2 Status

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
R18/19 in audio mute circuit (ctrl board) replaced by jumpers
Short out two resistors

More audio gain

All K2s after May 1999

¤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.
×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  
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
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

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


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

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

73, Sverre Holm, LA3ZA

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