With all respect, a healthy approach on these kind of problems should be ¡°what am I doing wrong¡± instead of blaming the FT847 to fail, to be dumb or to pretend it wants to be smart.
In most cases, the people designing a transceiver like the FT-847 are smarter than you and me.
If you can't "fathom" why they would use a hand mike's audio for a rig keyed by a computer, that's normal - because they don't.
The purposes of the PKT and? DATA IN/OUT connectors are explained in the manual on pages 16 (AFSK) and 17 (FM packet).
The PKT connector is for FM ( not to be confused with VHF/UHF).
The DATA IN/OUT jack is for AFSK ( not to be confused with HF).
All digital AFSK software ¨C no matter the frequency - ?goes via the DATA IN/OUT jack.
?
Also, the required resistor and the DC blocking capacitor are NOT there because of overload problems. They¡¯re there in order to add PTT functionality via the same jack.
The easiest solution to solve all your DATA and PTT problems is to aquire a Yaesu SCU-17 interface.
All computer connectivity go via a single USB connector and the connections to the FT-847 go via a supplied RS232 DB9 cable (CAT) and a supplied 3 pin jack cable (audio and PTT).