Building the Serial port cable

The first cable to build is the serial port cable. This will be a good way to do a quick test on the interface before you go further.

Use the Yellow cable for the serial port,  Strip one end of the cable back about 3 inches.  Cut off the foil to expose the red, black and bare ground wire.  The black wire isn't used but instead of cutting it off, twist it around the body of the exposed cable so it could be used later.
Strip the red wire about 1/4 inch back.  Tin this end and also the end of the bare wire.  Tin the two pins of the serial connector. ( Pins 5 and 7).  Now reheat the two pins and carefully solder both cable ends to the connector. The bare wire on pin 5 and the red on pin 7  The pin numbers are printed on the plastic, just hard to read.  Try not to use too much heat as it could melt the plastic.
Attach the metal cable retainer to the cable as shown.  The two short screws will attached the two pieces together with short screws from opposite directions. Only one end of each half is tapped, so make sure you line one tapped end on each side.
Put the retainer in the plastic cover as shown.  Make sure the bare wire isn't touching any other pins on the connector.
Snap the cover together.  The two screws on the connector end must be inserted before it's completely snapped together.  If it is snapped all the way, slightly pry it apart with a small screwdriver and insert the screws and the metal  guard while it's slightly open.  You might have to do this on both sides. Once the two long connector screws are in place, then you can install the two shell screws and nuts as shown -- This completes this end of the cable.
Prepare the other end of the yellow cable as you did before.  This time we will attach the cable to the board. 

 The red wire will go through hole H-19 and be attached to the LED at I-19  The ground will go through hole D-14 and attach to the common ground at F-14
This finishes up the serial cable.  Lets not go any further until we test the interface.  If you haven't already, you will need to download a program called digipan.  go to  and download and install the software. It's a great, free PSK-31 program. We will use this to test the interface.   Once it's installed, run the program.  If this is the first time you installed the program it will ask for your call sign, location and name. Fill that in and close the window.  Now click on Configure at the top of the screen. scroll down and click on serial port.  From that click on your serial port number.  Most times it will be COM1 but it can be anything. You might have to refer to your computer documentation if you don't know.  Once you set the com port make sure RTS is selected. But you can't go wrong with clicking on DTR also.  Click on OK to close that small window.

Now you have everything ready. Plug in the yellow cable to the serial connector on the back of your computer.  The LED on the interface should be out  If you click on the CQ button at the top, the LED should come on and you should hear the PSK tones in your speaker.  If your LED lights, congratulations, you have the complicated part of things finished.  If it doesn't,  lets check a few things.

Trouble shooting the LED not lighting:

  • Check that you have about -9 volts on the red wire from the interface when the program is idle.
  • The voltage should go to a Plus value around 9 volts when it's trying to send the CQ's.   If it is and the LED isn't lit, make sure the LED was installed correctly.
  • If the voltage don't change when you click on CQ then the problem is back on the computer side. It's most likely the wrong serial port selected.
  • If you don't hear the tones while the CQ's are being sent, then there might be a computer issue.
  • If all else fails give me a call and we can work it out.  I doubt it's a big deal.

The Club Website will have the latest version of these directions. 
Take a look at  or contact me at