Chris,
VAC has nothing to do with rig control or PTT when it comes to interfacing PowerSDR mRX with HRD or any other logger, digi mode program, or the like.
VAC gives you the
audio communications pathway between software applications. What you need to set up is a
control communications pathway between software applications.
The generally accepted way to do this where PowerSDR and HRD is concerned is as follows:
PowerSDR -- virtual serial port software --
DDUtil -- HRD.
There are three primary choices for virtual serial port software:
com0com,
VSPM, and
VSPE. I like VSPE the best, but it does cost a little bit of money.
I am not an HRD user, but I am a DDUtil user. My understanding is that, while you can make a direct connection between PowerSDR and HRD using a virtual serial port, people have had trouble with the stability of that configuration, and those who have used DDUtil have fared better.
I've not seen a very good tutorial on this subject, unfortunately. I did find a somewhat dated, and not entirely relevant, Youtube video, that should give you at least a general idea of what you need to do.
https://youtu.be/K1hZ6V9HMAMNote that there are at least two or three other ways to skin this cat, but the above method will provide full, bidirectional rig control.
73,
Scott
P.S. Since this is not a VAC problem, but instead a digital mode software interface problem, I am moving the topic to the correct sub-forum.