There is a BUG in WSJT-X V.2.2.0. when you try to connect the 991 you will see a “hamlib error” when you try to do the CAT connection.  Version 2.2.1 appears to have FIXED the issue.  If you are running V2.2.0 with the 991 upgrade to V2.2.1.

Some of you might might be new to digital communications on the ham bands, so let me start from the beginning.
Hams who are running PSK31 or JT65 or FT8/4 or some other digital mode are using a computer connected to an audio interface that is then connected to the radio.

The software on the computer generates audio that goes from the computer sound card to the radio as well as from the radio to the sound card.



There are several different types of interface devices that you can purchase to make this connection. BuxcomWest Mountain RadioSignalink, and even MFJ is getting into the market with their own audio device. I have tried the Buxcom, the West Mountain Radio (The M8, yeah.. a while ago!) as well at the Signalink.

This post is about setting up digital communications with the FT-991/991a, with only a USB cable. No external device required.
Yes folks, it is true. CAT control as well as PTT via one USB cable from the computer to the radio.

No USB to Serial converter needed, so additional interface boxes – just a USB cable (*Note, see farther down in the post as to which cable you want to purchase. Not all cables are made the same!)

The FT-991 comes with a built in sound card. Some say it is the same sound card that is in the Yaesu SCU-17, Yaesu’s equivalent of the Signalink device.  However, the FT-991 also do FSK RTTY as well as CW, (with its built in sound card) something that the Signalink cannot do.

“So, the FT-991 has a built in sound card. Neat Jay.. do I just connect a USB cable and go?”

Not quite cowboy, you have to take a minute (or in my case about 40) and do some research, find the right directions online and then follow them to make sure everything is setup properly.  The FT-991 packs a TON of features, and this can be confusing.

In this blog post, I did the research for you, and once you get all the software loaded, the right boxes selected and menu items changed it works!

So lets dive in here and get to it.


SET UP for the FT-991 using the internal sound card
(These directions are based on a Win 7 OS.  I have been told that in Win 8 and W10, you do NOT have to install the drivers first, but I think it is good practice to install the drivers before connecting the radio. To be safe, always install the driver before connecting the radio to the computer.)

Step 1. Read this post from start to finish
Step 2. Read it again
Step 3. Follow the steps below and do them in order
Step 4. If something isn’t working, revert to step 1

A. Do not connect a USB cable from your computer to the FT-991 until you load the drivers listed below. (See my comments above).

B. Go to the Yaesu web site and download the drivers for the FT-991.  The drivers you are looking for are the: FT-991/ SCU-17 USB Driver (Virtual COM Port Driver)  (3.74 MB). 

Some users might have a USB to serial converter based on the
chips (Prolific, FTDI).  These drivers will not work with the 991/991a.  You need to download and install the Yaesu drivers.

Download the FT-991/ SCU-17 USB Driver (Virtual COM Port Driver) and follow the directions to install them on your computer. (Just follow the prompts of the software during install and you will be fine.)

What will happen is that you will end up installing:

TWO (2) COM ports.

One is an ENHANCED COM port (in my case COM 4)
the other is a Standard COM port (in my case COM 5)

Now that you have installed the drivers, now you can connect a USB cable from the PC to the 991.  You might even hear the PC making some system beep noises as it realizes that it has been connected to an external USB device (the radio).

With the 991 connected you can check that these COM ports were installed on your machine by going to Control Panel, then Device Manager, and look under the “Ports (COM & LTP)” drop down.  You should see two newly added ports:

  • Silicon Labs Dual CP210x USB to UART Bridge: Enhanced COM Port (COM 4) (<–OR SOME OTHER NUMBER)
  • Silicon Labs Dual CP210x USB to UART Bridge: Standard COM Port (COM 5) (<–OR SOME OTHER NUMBER)

Again, your new ports might be numbered 3 and 4, or 6 and 7, or some other combination.  The key is that there are TWO of them, one is labeled Enhanced, the other Standard.

Note:  These ports will not show up unless you have the 991/991a connected to the computer via the USB cable.

I recommend the Triplite USB 2.0 Hi-Speed A/B Cable with Ferrite Chokes (M/M), 3-ft.  cable for the connection to the radio from the computer.  Other cables do not have the ferrite or may not have the shielding that you need to have within the cable.   MANY errors that show up with software crashing or Hamlib pop up errors, or folks crashing software when on 40m or high power on 20m are due to the cheap USB cables without shielding out there.  Get a quality cable and be done with it.    Lack of grounding and RFI issues are quick to present themselves when using digital modes.  If your keyboard starts to lock up, or your mouse, or the software starts acting sluggish.. check your grounding and address RFI issues.

** NOTE! **
If you have different radios that you are connecting to the same laptop for digital (in my case, a FTDX1200 and the FT-991), PAY ATTENTION to the different COM ports that are assigned and make sure your are using the correct “pair” of  standard and enhanced ports.

Know what you have installed.
Check them in the System Properties!

Once the drivers are loaded, it is a matter of getting the digital software that you want installed and setting it up to talk with the USB port on your laptop.


USB drivers (Win 7) HAVE TO BE installed first.


If you do not install the driver first, NONE of this will work.
Just stop reading now.  Stop reading and install the driver from the Yaesu site.  Here is the link again.   Once that is done, then move forward to the next step.

Yaesu FT-991 MENU SETUP:
(If you have a 991(A), your menu numbers will be slightly off, just go by the menu name)

DO this before trying to configure the WSJT-X  or any other software on the computer.

These are the MENU settings that I changed from the default values.
031 CAT RATE 4800 (or faster – just make sure the software and radio match the same CAT RATE many are using the fastest “38XXX” vale.  I use 4800 and it works fine.)
032 CAT TOT 100ms
062 Data Mode  OTHERS  (NOT PSK – change to OTHERS)
064 OTHER DISP (SSB) = 1500 Hz
065 OTHER SHIFT (SSB) = 1500 Hz


Yaesu FT-991 Screen settings:

These are the settings on the main screen of the FT-991 that I adjusted.
MODE:  DATA-USB  (NOT USB), choose the DATA-USB setting.
WIDTH: 2400 or 3000
METER: ALC (I use an external meter to watch RF power out)
RF PWR: 8-50w  start low and work up.
WIDTH: 3000
NAR/WIDE: W 3000
DT Gain:  6   *** IMPORTANT ***
The DT Gain defaults to 50!   This will overdrive the rigs modulator which will cause unwanted audio harmonics.  Not good.  Turn the DT Gain setting down to about 4, and start working your way back up, watching for ALC on the meter as well as the power out that you want.  As you move the DT Gain setting back up (higher), you will see your power level increase as well as ALC levels.  Find the happy medium of NO ALC showing on the meter.   Excessive ALC indication is a sign that the audio drive is too high and distortion is most likely happening.


With all the updates to the software, it is best to just get the latest release when it is available.  Running outdated versions will lack features and in some cases not allow you to work stations running the new software.  SoUPDATE the software when the new versions are out.

You can get it here:

Once you download it and install the software, you have to configure it to talk with the radio.

CONNECT THE USB CABLE from the computer to the FT-991 NOW.

Start the WSJT-X application.

Below are some OLDER screen shots.  They are for reference only.  The latest version of the software will have additional selections, however, the layout is similar.

Then click on [FILE] and then [SETTINGS].

Here is where you need to select the right options to connect the FT-991 to your computer.

Here is an older screen shot of what works for my setup.

screen shot wsjt-x

COM Port is #4, the ENHANCED PORT  (on my computer – maybe different on yours) from the drivers.

4800 baud (or faster if you desire)
8 data bits
2 stop bits
Hardware: Handshake
Poll interval: 1 second
CAT control: via COM 4
Mode: NONE
Split:  FAKE IT OR RIG  (YES, I KNOW… I have NONE selected in the image above) choose FAKE IT or RIG.

*** It is very important that you select Fake It or Rig when using the newer versions of FT8 due to the advancements in the software and the way the software operates. ***

Click on Test CAT.  It should turn GREEN.

Click on Test PTT. It should turn RED and you should see the radio switch into TX mode, (no RF out).

Supposedly all you need to do for Windows 10 is the same as I did in for Win 7/8.

Once you are done with the [RADIO] tab, click on [AUDIO].
screenshot of audio settings

Set WSJT-X sound card Input AND Output settings to USB Audio CODEC.
Do not select the default sound card or microphone or any other software you have in there.  You want the “USB AUDIO CODEC” as the selection.  This new audio option should populate automatically in the drop down for the input and output option, now that you connected the radio to the computer.
You DID do that before you got to this point yes?


Note: You may see USB Audio CODEC -7 or -8. (Or some other possible number)  That is fine as well.  Just select the USB AUDIO CODEC.

Set the TX level (on the far right side of the software) to the top of the scale.  Adjust the DT GAIN setting on the FT-991 so that ALC is not observed (or barely observed) on the meter on the FT-991 radio.

right side of jt-65 software meter

PAY ATTENTION to your ALC settings. This is done by watching the DT GAIN setting on the front panel of your FT-991 and monitoring the ALC screen (switch from PO or SWR to ALC).


Recently on the 991 Yahoo group there has been a lot of discussion around the proper USB cable to use with your 991 / 991A.
RF floating around and poorly made cables has made some connections intermittent and or drivers would not load.
The recommendation is to use Tripp Lite Model U023-006 USB 2.0 Gold X Cable A (Male)/B (Male) – 6 ft with two molded chokes.  Amazon Prime cable at $6.51 delivered.

I wound up using a USB cable with inline chokes that I found on Amazon. "Tripp Lite USB 2.0 Hi-Speed A/B Cable with Ferrite Chokes (m/M) 6-ft (U023-006). That solved my RF problem. - Jon  AA4JS

A follow up by Don, K0APK.
It completely got rid of my RF-induced problems. I liked it so much that I bought 5 more and replaced ALL of my USB A/B cables in the entire  house!
No more lock-ups of programs, resets, and dropping of my wireless links when I keyed the transmitter!


From Gary, WW8O – This is the setup for a USB cable and Singalink.
NOT using the internal sound card in the 991, but rather the external Signalink device.    Has has had this work both on wsjt-x and fldigi.

991 (or /a)  
Menu Setting:
31 38400
60 rts
62 other
63 1500
64 790
65 1500
67 6db
68 4000
69 6 db
70 rear
71 rts
72 data
73 20
108 rear
110 rts
111 usb


* NOTE 991A, but should be similar with the 991 *
I was asked to share all the settings that I arrived at for successful FT-991a with Fldigi and RigCat operation.  

FT-991a (all other settings are defaults)

Menu Number  Function           Setting                  Notes

031                         CAT Rate    38400                  Must match fldigi CAT rate

032                         CAT TOT                     100 ms

036                         TX TOT                       3 min

059                         CW Freq Display       DIRECT FREQ

062                         Data Mode                   OTHERS

064                         Other Disp (SSB)               1500

065                         Other Shift (SSB)              1500

066                         Data LCUT Freq                  OFF

068                         Data HCUT Freq                  OFF

071                         Data PTT Select                 RTS

072                         Data Port Select                USB

108                         SSB PTT Select                   RTS

109                         SSB Port Select                  USB

142                         VOX Select                          DATA                     Must also turn VOX ON (M-LIST)

                                                         Observe D.VOX indicator is ON 
 (upper LH corner of display)

M-LIST Settings:                                                       FLDIGI Settings (Configure > Rig Control):

VOX = ON                                                               FT-991.xml file loaded

NOTCH = OFF                                                             Device = COM3 (enhanced port)

WIDTH = 3000                                                            Baud = 38400, Stop = 1, RTS/CTS flow control

RF PWR = 50


Hope this saves you some brain cells!!

Mark, WA0ZIG

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