User Guide

2
( ) Remove the small white wire from the center contact of the “antenna relay” jack. Remove
the other end of this wire from the solder post near the coax connector.
( ) Route the BLUE wire from the SK-301 under the circuit board and connect to the center
contact of the “antenna relay” jack and solder.
( ) Connect the YELLOW wire from the SK-301 circuit board to the solder post where the white
wire was removed and solder. Note, there is a 39Ω resistor also connected to this post.
( ) Reinstall the left corner piece and rear panel onto the chassis. Place the chassis back into
the case.
This completes the installation of the SK-301 “Soft Key” module. You may not SEE any
difference in the operation of your exciter or amplifier, but you will know that you have reduced the
stress on the exciter’s keying relay by many orders of magnitude.
SK-301 “SOFT KEY” MODULE
HARBACH ELECTRONICS
Jeff Weinberg – W8CQ
468 County Road 620
Polk, OH 44866-9711
[phone]
http://www.harbachelectronics.com
[e-mail]
PARTS LIST
R1 200KΩ ½W 5%
R2 10KΩ ¼W 5%
R3 2KΩ ¼W 5%
C1 100µF 10VDC
C2 0.1uF 50VDC
D1 1N4005 (1A 600 PIV)
D2 1N5817 SCHOTTKY (1A 20V)
D3 1N60 GERMANIUM
IC1 4N33 OPTOCOUPLER
Q1 IRF9610 HEXFET (P-CHANNEL)