This interface is well known and works with many logging or contest softwares. It sends CW and makes the PTT switching.
I only want to share my experience and design.
It uses SMD components, so it can easily fit into the LPT connector. I use it with all my software, LOGGER, WIN-TEST...
For this construction, i used SMD components coming from old recovered printed boards. I was able to put the printed board + components in a DB25 connector.
The SMD transistors are BC548B, but any NPN type of SMD transistor with same pining will do the job.
Pin 1 of the DB25 connector is the ground return of the transistors, and you can't drive to much current, so be careful ! The connection between this pin and the printed board, as well as grounding the connector case are done with small wires on the opposite side of the board.
Here is the data sheet for the BC548B in PDF file format.
Download the printed board file to be used with the SPRINT LAYOUT sofwares. You can get a demo version and a free reader here on ABACOMs page..
Component placement and printed board.
First published 20/11/04