There is an undocumented CAT control port for the FT-857D through the microphone Jack. You can find it with a google search. It took me about an hour to make the device on a bread board exactly as shown in the schematic and it worked flawlessly. I have a tremor in my hands that makes soldering rather difficult. A couple of small venders offered the cords already made up but the one I purchased did not work because the maker tried to simplify the circuit in some way. Here is the web address for the one I successfully breadboarded. <>. This leaves the CAT jack available for a tuner or amplifier control. I have used my FT-857D that way with the SGC SG-230 remote tuner, more correctly an antenna coupler, and the set up worked quite well.?
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It's connectors are serial to USOC modular microphone jack so you will need a USB to serial adapter. Be sure that the adapter that you buy has a genuine FTDI chip set. In use with radios the prolific chip set has acquired a reputation for poor performance. There are a lot of counterfeit chips out? there so look for the brands that are specifically mentioned as genuine is the non vender comparison articles. Even though the sales and catalog descriptions call the connector you need a DB9 that is actually erroneous because the Serial connector is actually size E as in D form, size E connector, 9 pin. I don't know were the habit of calling all D form connectors size B but, in general, it doesn't do any harm because nearly the entire industry uses this misnomer but pay attention because there are a few DB9s out there that are actually the common B size but actually have only 9 pins. Those are used in? gender changers and a few converters.?
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Tom Horne