As you could read in the articles posted about operating techniques (go back to main page and look for that page), generating CW with a PC with logger IS A MUST for any serious contester and is very comfortable for DX-peditioning and for DXer that are very very lazy (like me...!). As you could see from the picture above (my poor shack at EU 130!) I have always a PC dedicated to serve my transceiver for logging and CW generation, using also Packet Cluster SW, sound card virtual TNC and a small VHF rtx to monitor what is going on out there !
The various loggers & contesters programs (I have a section devoted to choose
the right logger based on which PC you have in the shack !) offer the capability
to use a serial port (COM1....COM4) or the parallel port (LPT1) to key your transceiver.
So now you need a proper interface circuitry for one of the above mentioned port.
There are very simple -one transistor- circuitries in the loggers manuals but despite simplicity they connect together the ground of your PC and the ground of your Transceiver.
But your PC is a valuable equipment and you sure don't want to burn any port with RF
return on PC ground !!! This is not a theoretical thing, I personally (sigh!)
destroyed one laptop pc motherboard operating with just the 100W of an IC706
and a such simple not isolated interface on LPT port !
So here following the desirable features of any PC to RADIO interface :
Galvanic insulation between PC and Transceiver.
Immunity from RF fields, avoiding hanging up when trasmitting or creating RF returns.
Small size.
Few parts and simplest usable circuitry.
No necessity for external power supply.
Robustness in construction for reliable Field Day or DX-pedition use.
To be usable with the most common loggers or CW PC-typing programs.
To fulfill all these basical requirements I decided to designed, based on optocoupler devices, a series of small interfaces for both serial and parallel port.
The first model is for generating CW with most common loggers programs (CT,TRlog,N1MM
etc)
The cost is 15 Euro (shipping excluded) for a fully tested and working device with connector and cable for transmitter keying.
See photo below and related pdf
A parallel port version (stays within DB25M case) could be also requested, at the same
price.
These circuits stay inside the DB9 or DB25 connector case to minimize RF returns 
and for providing robustness to the realization. See for example the pictures below,
where a serial port interface is depicted in details:
optocoupler based PC serial interface for CW
generation
The circuitry is very simple, and if you want to build by yourself such circuitries,
you could use a breadboard, just download the following pdf :
For the parallel interface, for the PTT circuitry, the right NPN transistor depends on the external circutry of the amplifier, in terms of max current for keying; for driving a relay inside the linear amplifier, just try with a BC879 or equivalent.
Just in case you will need more details, or the PCB files
this is my e-mail address; you could also build the parallel
version with only the CW part, if you don't need to key an amplifier.
This is an UNIVERSAL MULTIMODE PC to RTX insulation INTERFACE, for operating AFSK / CW in RTTY/PSK31/Packet Cluster/CW & Voice Keyer (using for example N1MM logger SW) with a PC equipped with soundcard.
Comparing to simpler models it includes the circuitry of PTT and could be connected with a terminal box to serial or parallel port according to user needs. It employs two optocouplers for galv. insulation, a comm. transistor for PTT driving, two insulation transformers for audio signals and is RF immune, and has terminal blocks for easy wiring - SOLDERLESS.
Works fine with almost any PC from old 486 to latest powerful laptop !
The cost is around 40 Euro (shipping excluded) for a fully tested and working device without connectors and cables for transmitter keying and PTT (the cabling changes according to your radio and chosen port for keying, so this makes sense...)
The circuitries have been tested in several contests & field days and work properly in presence of very strong RF fields.
Shipping time & payment form to be agreed.
The circuitry is very simple, and if you want to build by yourself such circuitries, you could use a breadboard, just download the following pdf .
You could download the schematic or the files of the magazine article that was published on an italian magazine for hamradio in the 2004, but sorry, and detailed instructions for various type of transceiver (in Italian language) :
If you want to have additional infos do not hesitate to send me a mail!