The official Elecraft site lists all the mods and updates for the KX3, but doesn’t collect those with serial numbers in one spot. I’ve made a list of the ones documented.
This does not include builder’s notes or calibration procedures like the Extended VFO Compensation Procedure. Those are useful, but are not hardware mods associated with serial numbers.
|Modification||Factory Serial #||Kit Serial #||Part #||Documentation/Notes|
|160M/80M Rx Performance Improvement||1845-2045||1845-2045||N/A||160M/80M Rx Performance Improvement|
|BNC connector with low-pass filter||2406||2492||KX3BNCMDKT||Reduces VHF radiation from HF antenna jack|
|Tuning Noise Suppression||4668||4753||N/A||Tuning Noise Suppression|
|Enhanced Heat Sink||7255||7292||KX3HSMDKT||Enhanced Heat Sink|
More info on the 160M/80M Rx Performance Improvement from the app note:
The Performance Improvement applies only to RF Boards Revision C or earlier. The improvement has already been incorporated into KX3 RF boards Revision D. Revision D boards were introduced in KX3 serial numbers between 1845-2045. KX3s in this range will require inspection to determine the revision installed.
Changes have been made to 4 SMD parts on the RF board. Due to the density and small size of these components, Elecraft recommends that owners of KX3s do not attempt to make the modification.
This is a design improvement and the modification can be made by Elecraft.