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 http://kavea.free.fr
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 (http://k0lee.com/ft100/pskft100.htm) but with an additionnal protection from OZ6YM (http://www.planker.dk) 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.