Weak Signal Digital Modes on HF-Bands

Many open source programs are available for Windows, OS-X and Linux, if you want to become active on the amateur radio HF bands using digital modes. Modern coding and modulation schemes allow for long distance contacts with low power.

Below you can  download my presentation about PSK 31 (Phase shift keying) and JT-65/JT9 modes as presented in our monthly SARTS meeting August 2016 in Singapore.

Presentation (pdf): WeakSignalModes


IC-7300 and Fldigi

For digital modes I am using fldigi on a MacBook and the IC-7300 built-in USB interface. This is my running configuration:


On the IC-7300 press Menu -> Set -> Connectors

ACC/USB AF Output Level to 75%

USB MOD Level to 25%

Under CI-V CI-V Baud Rate is set to Auto.

CI-V USB Port: Unling from [REMOTE] and
CI-V USB Echo Back: ON


You need to get the IC-7300.xml file written by W1HJK to use the CAT.
After Installation start fldigi and go to
Configure -> Rig ->RigCat
Select the downloaded xml file. Under Device select “SLAB_USBtoUART” (driver name).
Set Baud rate to 19200.
Tick CAT command for PTT
Audio Port: Audio USB Audio CODEC
The “sweet spot” for the IC-7300 in data mode is 1500 Hz.
Configure -> Misc -> Sweet Spot PSK et al.: 1500


Reduce the output power to 20% … 35%. When you click on “Tune”, ALC should be at zero. In my station setup I can “hear” the computer on 15 m. Levels vary depending on the USB connection cable. I still need to experiment with some ferrite to reduce interference.
The same configuration can be used for JT-65 (WSJT-X). I changed the IC-7300 CI-V address to  88h and select IC-7100 as transceiver.