Unlike other transceivers in FT-8xx lineup, Yaesu FT-891 does not expose the serial interface lines and instead implements serial CAT internally via its own USB connection.
Only the cable with MiniDin6 connector is needed on the transceiver side. Plugged into Digirig’s audio port it takes care of minimum feature set required for digital modes: audio and PTT. The PTT switch is controlled via the RTS signal of Digirig’s COM port.
I have a stupid question. In the diagram you have two cables, one of which is the usb A-B which is not used with the DigiRig. That leaves one. In the link for the kit there are two cables so I’m confused. Which cables do you need for the 891? You say only the MiniDin6 connector is needed but the kit has two.
The kit is for all Yaesu FT-8xx transceivers. All of the models in this family except for FT-891 use two cables: one for audio/PTT, another for serial CAT control. The serial CAT control in FT-891 is implemented differently so the 8 pin MiniDin CAT control cable is not used with this model.
I don’t have a separate listing for MiniDin6 cable but if prefer to only order one cable, you can order 9600 baud cable and leave a note that you want 1200 baud pinout cable for FT-891 instead. Don’t forget to leave a note though: if not swapped the 9600 cable will not work for FT-891. That’s another quirk of that transceiver.