Building a COM Port Keyer

I decided to make up a COM Port Keyer for my Link Station set-up here. Why build a Port Keyer?

With a basic Link station setup, the Link station radio will be triggered by using VOX. VOX stands for Voice Operated Transmit. This will mean that any sound coming out of the Link station PC will trigger the radio into transmit. Unfortunately when using VOX on the Link radio, the very first few tenths of a second of audio are missing. The small delay is caused by the Link radio detecting the sound level and then deciding to trigger the radio into transmit.

Using a Port Keyer (which connects to the Link station PC via the Serial Port) will remove this small delay and make the PC trigger the Link radio into transmit directly.

Two very useful websites denoting how to make this little beauty are the 446User Website, and the UK152 Link station website. I thought I would add to the fun with this page of my own :-)

Here is the circuit diagram:

Opto Circuit

There is effectively only one six pin IC (an Opto Isolator) and three discrete components to worry about.

I decided that my effort would be 'small' - Small enough to be able to fit into a standard plastic DB9 housing.

Keyer 1

Note in the next photo that the resistor and diode are mounted upright and together to save space.

Keyer 2

Fits snugly into the plastic housing.

Keyer 3

Et voila - The finished article. All built from scratch in about an hour.

Keyer 4

Now to set the Com Port Keyer up in the eQSO software. Note a few things I have highlighted, which have had to be changed. The Rig Control method is now 'Com Port' I plugged my keyer into Com Port 1. The Keyer uses the DTR line to trigger the transmit, and the voltage does not want to be inverted.