Elecraft K2 Keying Modification Instructions Bedienungsanleitung PDF herunterladen

Elecraft K2 Keying Modification Instructions

Rev. A, Feb. 3, 2004

Introduction

The modifications described here significantly reduce the K2's CW keying bandwidth, while not making

the keying too soft. This change is recommended for all K2s, but is especially important for stations

operating at high power, which are more likely to interfere with nearby stations. NOTE: You must

update your K2 firmware to revision 2.04P or later when you make these changes (see next page).

Technical Details

Recent analysis has shown that the keying bandwidth of many transceivers is excessive. A consensus has

emerged that a sigmoidal (S-shaped) envelope, rather than a classic R-C exponential envelope, is ideal.

The K2 can be modified accordingly. As shown below, the new keying waveform has longer rise and fall

times, and the abrupt falling edge is eliminated.

Most of the changes are in the key shaping circuitry (U10A, Control board). The R-C shaping network is

reconfigured as a two-pole low-pass filter. In addition, a capacitor is added from the VPWR line (U8 pin

2) to ground to reduce the slew rate of the power-control DAC signal. Finally, a high-performance PIN

diode replaces the original D36 on the RF board to prevent control signal leak-through during keying.

1 2 3 4

Inhaltsverzeichnis

Seite 1 - Technical Details

1Elecraft K2 Keying Modification InstructionsRev. A, Feb. 3, 2004IntroductionThe modifications described here significantly reduce the K2's CW ke

Seite 2 - Preparation for Modifications

2Parts InventoryAll parts to be changed or added are on the Control board except D36, which is on the RF board.Ref. Description Qty. Part No.C31, C46

Seite 3

3Changes required to the K2 Control BoardOn the top (component) side of the Control board, CAREFULLY cut the PC board land runningfrom RP2 pin 2 to U1

Seite 4

4On the bottom (foil) side of the Control Board, Install the .01 µF ("103") capacitor (C46) from Q8-base to the junction of D3 & R21.On

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Elecraft K2 Keying Modification Instructions Bedienungsanleitung

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