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Icom CAT Control Guide

Icom transceivers seem to be the most difficult ones for ham radio operators to set up and it is mainly due to the way the Icom CAT system works.

In the case of Kenwood, Yaesu and Xiegu radios, the CAT port is designed such that your chosen CAT or Digital mode software connects to one radio. So a COM Port on your PC connects directly to just one radio.
If you want to connect to a second or third radio, you have to use a two or three COM ports etc.

Icom CAT (or CI-V) can access multiple radios on a one-wire bus. If you want to learn more, see my description of the Icom CI-V interface
here. This means that each radio needs to be addressed so that the software knows which radio it is talking to on the single bus. Most CAT or Digimode software can't make use of this feature but you do need to make sure some settings in the radio are correct for the software to establish a connection.

But first the basics. Lets look at an example of the settings screen in WSJT-X to understand the settings we need to work on. Things the software is intested in are the
Radio Type, the COM port number and the CAT control baud rate. I am basing these instructions around Windows but the basics apply for MacOS and Linux.

CAT Settings helper.JPG

So you have plugged your CAT cable or Digimode interface into your PC. How do you know what its COM port number is? Well the easiest place to look is in Windows Device Manager. If you type "Device manager" into the Windows search box on the task bar, you can run the device manager application.

Look in the Ports (COM & LPT) section and the available COM ports will be listed. COM1 is almost always the legacy serial port either built onto the motherboard of your PC or available as a DB9 male on the rear of older PCs. If you are using a USB CAT cable or USB Digimode interface with built-in CAT control, it will not be on COM1.

In our example below, our interface has been allocated COM5. If you have multiple devices plugged in and are showing lots of COM ports to choose from, the simple test is unplug the cable/interface you are working with. The list will update and the one you have unplugged will vanish from the list. So that's the number you want.


Remember the COM port number as you will need to enter this in your software.

Device Manager Grab.JPG

In my example I am setting up an Icom IC-718. So you would think its as easy as just choosing the IC-718 in the radio type drop-down menu in the software. Well in 99% of the cases yes. But I mentioned that the Icom CI-V protocol uses addressing. And so your Digimode software expects the radio to be on its default CI-V address. But you can change this address to what you like in the radio.  So its best to go into the SETMODE Menu on your radio and make sure the CI-V address is as expected. It is worth noting that the SETMODE sections in different radio handbooks look a little different and so use this as a guide.

In our example the IC-718 has a default CI-V address of "5E". Check your own radios handbook and ensure the
CI-V address is set to your radios default setting. And a word of warning....  An IC-756Pro, Pro2 and Pro3 all have different CI-V addresses. So make sure you select the correct version of your radio in the software.

CIV Address.JPG

Next we need to set the Baud Rate. Now in reality, the actual speed does not matter. 9600 baud is a good speed to go for. So by all means, set your CAT or Digimode software to say 9600 baud. Most Icom radios have their CI-V baud rate set to Auto in the SETMODE menu as below. Feel free to set this to 9600 or whatever you have chosen in your software. I like to fix the rate in my IC-718 and so I have it set to "96" which is 9600 baud.

CIV Baud Rate.JPG

Now the next SETMODE menu setting will completely mess up CAT control if it is not set correctly. The early IC-735 had a 4-byte sized CI-V packet. Where as most Icom radios are 5-byte.  If you have your radio set (accidentally) to 4-byte mode, CAT control simply will not work.
So make sure in your radio SETMODE menu that "
CI-V 731 mode" is turned off.

731 mode.JPG

And the final check on an Icom is the most obvious. The CI-V jack is a standard 3.5mm jack and many Icom radios have multiple 3.5mm jack sockets on the rear panel. I have had MANY customers who could not get CAT control to work only to discover they had plugged the CI-V (CAT) plug into an adjacent 3.5mm socket!!!

If you have followed this guide and checked the SETMODE options in your radio are as expected, then there is no reason why you can't get the CAT control on your Icom up and running. The port on the Icom radios is well protected and robust and so it is incredibly rare for an Icom to not have CAT control due to a faulty port on the radio. It's invariably a set-up/configuration issue.

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