Philippine Amateur Radio Association Inc. (PARA / DX1PAR)
Philippine Amateur Radio Association Inc. (PARA / DX1PAR)
I have built a DIY interface for my ICOM 718 HF radio to send and receive audio signals to a laptop computer and control the PTT keying, for use with various digital modes such as FT8. I used a USB sound card for the audio interface, and a USB-to-serial port adapter for PPT keying. The audio output of ICOM 718 (from speaker out or Pin 12 in the accessories port) connects to the microphone in of the sound card (pink port, microphone port). The audio output of the sound card (green port, headphones port) connects to Pin 11 of the ICOM 718’s accessories port. The USB-to-serial port is then configured in the settings tab of the software WSJT-X to send pulses to the the serial port’s RTS pin, which then controls a BC547 transistor to key the PTT (Pin 3 in ICOM 718’s accessories port) when transmitting a signal.
The circuit board of the USB sound card and the USB-to-serial adapter are then removed from their housing and soldered directly on to a USB hub. This configuration allows both modules to work with just one USB port of the laptop. I then put everything inside the metal casing of the radio, in a section protected from radio interference. To operate in digital modes, I only need to connect one USB cable from the radio.
During my initial tests, I was able to contact a station in Brazil (South America), from the Philippines, at 21.074 MHz (15 meters), using a 40-meter band center-fed dipole wire antenna resonant to the 15-meter band.