Why would you use this combination?
I would not use this in a EOC or Club station with multiple operators, and the reason is... If someone changes or deletes some of the setup you are off the air until someone can get it back running again.
They need know how the setup is configured to get it back working again.

I doesn't have Node capability, so no Node support the Packet Network

It would be good as a personal station if you already owned a Yaesu FT-991A
If you are dedicating into packet then there is a better solution.

I would recommend a Motorola with a Kantronics KPC series TNC that supports a KA or K-Net node. That would support the Local Packet Node Network too.

( only a USB A to USB B  cable required)

Go to: UZ7HO SOFTWARE  (Version 1.14)

Download file:  

Extract to folder - c:\uz7ho

Run the UZ7HO soundmodem.exe

Select AFSK AX.25 1200bd & 1700


(I changed all parameters ch: A & ch: B  to be the same)

Change as per this screen shot


Change as per this screen shot


Type, Sound in the Windows search box

Click, Change system sounds

Setting - Playback

Double click on the USB Codec for your FT-991A

Then click on Levels

Set the level to: 75
Then click OK

Setting: Recording

Set the level to: 75
Then click OK

That sets the computer USB levels to and from the FT-991A

Winlink Express

Open Winlink or P2P to do the setup

YAESU FT-991A setup:

On the front panel short press MENU -
Start with all menu item set to default (they will be Blue)

Any changes you do will change to white

Menu # O31 - 38,400 bps (optional you can set to what speed you want)

Menu # 077 - USB
Menu # 142 - DATA

On the front panel short press "F" (Function)
Scroll to VOX and turn it ON
Note: Make sure that you set TONE/DCS to OFF

Choose your (TX) USB Audio Codec when using Packet!
(yours may say someting different)

Now you should be all set up!