The FT-991a is well known for being sensitive to RFI on the USB port
I use a short USB cable (about2 ft) with a big ferrite near the rig and the USB cable fed through it about 4-5 time
And coiled about 5-6foot of coax into a 5-6 inch coil with about 8 turn where the coax enters the shack, and I have no issues
Sent from Mail for Windows 10
From: main@WSJTX.groups.io <main@WSJTX.groups.io> on behalf of RichW6BOT <rich.allen.gordon@...>
Sent: Friday, July 30, 2021 2:01:28 PM
To: main@WSJTX.groups.io <main@WSJTX.groups.io>
Subject: Re: [WSJTX] Setting Up WSJT-X with Ft-991a with a raspberry pi #FT8 #linux #Yaesu
More than likely you have an RFI problem.
I have an MFJ current balun on my dipole, and a large ferrite on the coax between a switch and the 991a. I still have to keep the Pi a couple feet away from the coax in order to keep my bluetooth keyboard and mouse from losing connection.
I'm second story with no easy way to RF ground the equipment.
Glad you have the two talking at least!