Last days i did some experiments controlling the FT817 via CAT. I implemented some basic commands in the math scripting environment Octave (which is a Matlab compatible software). The communication with the serial CAT interface is not possible directly because Octave does not support serial communication. Therefore i used the VSPE (virtual serial port emulator) to connect the serial port to a TCP port which can be addressed out of Octave.
I wrote a script that can tune over a frequency range and reports the signalled S-meter output. In the end a diagramm of the S-meter output versus frequency is drawn. If you have a narrow filter (e.g. 300Hz CW) than you may use this to get somewhat like a “spectrumscope”. Compare the two pictures below which show a D-Star signal in 70cm band recorded with the FT817 and with a R&S FSP spectrum analyser. It is clear that there is a low dynamic range and no information what the S-meter readings correspond to in terms of dB but it comes more or less for free.
Short guide: switch transceiver to desired modulation mode and filter bandwith, edit the frequencies and stepsize in the main scan script, start the VSPE software with correct settings, edit the ft817_connect.m script accordingly, start the scan script.
Find some scripts here: octave_ft817_cat_scripts