YT1DL Only Digital

Digimode PC to TRX galvanic isolated Interface

This interface is galvanic isolation of the transceiver from PC computer. Audio input and output paths are separated by transformers; optocouplers serve to isolate the digital paths, PTT and CW KEY.

It was built for Icom IC-718 but can be used for any other radio. Interface support PTT keying over RS232 RTS (pin 7) and CW keying over RS232 DTR (pin4) line. LE diode LED2 glow green when radio is in RX state. LED3 glow red when PC software switch radio to TX state. If you use some of contest or logging software for automatic CW keying, LED 4 will glow in rhythm of Morse letters.

Connection from PC to interface goes to 9 pin subD female connector. It takes 3 pins:


Connection from interface to TRX goes via 9 pin subD male connector. Same connector is used for audio channels from interface to TRX. This is connection cable for ICOM IC-718.

Interface Description Icom
Sub D - male
13 pin ACC Socket
PIN 2 PTT 3 - Send
PIN 3 CW Key
PIN 8 Line out PC 11 - Modulator input
PIN 9 Line in PC 12 - AF detector output

Schematics diagram

Schematics made with Abacom sPlan. Download free viewer at


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PCB layout and parts placement

PCB is simple, one sided. I use toner transfer method to make this one. There is instruction for this method at my site. For now it is only in Serbian, but soon, it will be English to. Here you can find PCB layout in different formats so you can choose what is best for you. PCB layout made with Abacom Sprint 5.0. Download free viewer at

PCB layout


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PCB and parts placement


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I did not save PCB space so everything can be accessible and logically placed. You can notice that I used old PC mother board connectors for sound input and output. Two reasons for that. First, it is easy to find old PC mother boards at my scrap pile, and second, it's hard to make mistake in audio cables if you use connectors of right colors. So, just connect same color at interface and PC side.