Introduction: Yaesu FT-100 PC Link Interface for Digital Modes

Here i present the guidelines to build a PC link interface for Yaesu FT-100. This interface alows you to transmit and receive audio signals from a sound card in order to operate HAM digital modes (FT8, PSK31 etc.).

Additional information is available on my blog

Step 1: Materials

You will need these components:

- 600 ohm 1:1 transformer (e.g. Bourns LM-NP-1001-B1L) (2 pcs)

- NPN transistor 2n2222 (1 pcs)

- Diode 1n4148 (2 pcs)

- Trimmer 1kOhm (2 pcs)

- Capacitors and resistors (cf. step 2)

- DB9 connector (1 pcs)

- Jack 3.5 female connectors (2 pcs)

- Some box

Step 2: Schematic and PCB

The PTT command is based on the work of WA2NKF ( but with an additionnal protection from OZ6YM ( on audio channels. This protection is based on a 600 ohm 1:1 transformer and avoids the damage of the rig from a DC voltage present on the output of the soundcard.

The sound level on a soundcard lines is adjusted with a 1 kOhm trimmer. In order to trig the PTT a DTR (pin 4) or a RTS (pin 7) signal can be used. In my case i use a DTR.

The circut was designed on KiCAD and milled on a CNC machine, but you can use a standard etching method. Gerber files are available on my blog.

Step 3: Fabrication and Assembling

Solder all components and put into some box. Be aware, the pins of the transformers should be isolated from the bottom ground plane.

Enjoy !