Connection to the radio
The Links page of the website lists sources of ready-made cables that can be ordered over the Internet as well as several DIY circuit designs.
If you already have a programming cable for a Yaesu radio that uses a 2-wire circuit you can make an adapter to plug into the microphone socket. Pin 4 is ground and pin 6 is data (see page 48 of the user guide).
Direct USB port attachment
Cables that connect directly to a USB port are now available from a number of sources in the USA, UK and Europe. This type of cable is directly powered from the USB port and is the recommended means of connection.
9-pin serial port attachment
Connection to a 9-pin serial port can be achieved using a cable such as the RT Systems CT-29F.
The CT-29F cable incorporates a voltage level converter to convert between the +/- 12V of RS232 to the +5V/0V of TTL voltage levels needed by the transceiver. It also converts the 3 wire RS232 circuit (TX/RX/GND separate wires) to the 2 wire GND/TX+RX used by the radio.
If your level converter takes its power from the serial port (as does the CT-29F) you may have problems in acquiring sufficient power for reliable communication - particularly with laptop computers. See here for a test you can perform on the voltage level available at your serial port.
Voltage level from the programmer
The author found that the voltage level across pins 4 and 6 had to be 3.6V or more before reliable communication could be achieved with his FT-1802. To measure the voltage on your programmer plug the cable into your PC leaving the RJ12 connector free. Run the program. Click the Read Radio button and then check the voltage.
Selection of the Com port number is done using the Settings menu. The program will remember the selection you make for the next time you run. If you are not sure what Com port numbers are available on your PC you can run the utility program CommTest which is available on the author's website