Computer Keying Interface for the K2

When operating CW contests with the Elecraft K2, I use the 'SD' computer logging program (DOS version) on an old Toshiba laptop (Model T1850).  The Elecraft RS-232 interface provides rig control; and this homemade computer interface is used for keying the K2 from the parallel port.

Components:
C1-C7 are all 0.01 uF
D1-D6 are all IN4148
L1-L6 are all 300 uH or 470 uH chokes
SK1-SK2 are both 1/4 inch stereo sockets

C1/C2/D1/D2 are not necessary if SK1 will only be used with an external paddle.  SK1 and SK2 are fitted with 1/8 inch reducers, as required.

The main components are mounted inside a small plastic project box measuring 71 x 50 x 25 mm.  A 1.5 metre length of 4-wire screened cable is used between the 25-pin D connector and the project box.  The keying lead between the project box and the K2 uses 2-wire screened cable (salvaged from a discarded pair of stereo headphones).

Feedback from other constructors

No feedback has been received so far!