As far back as I can remember I’ve been interested in electronics and radio. In my early years I loved to disassemble TVs and radios. I didn’t know how they worked, but I loved taking them apart to add parts to my junk box for the future projects I hoped to someday build. My grandpa gave me his old issues of Popular Electronics from 1956 to 1960 and I spend many hours dreaming about and sometimes building projects from those issues.

When I was 14 I earned my Novice license, WN7QYG. Later that year I upgraded to General as WA7QYG. Ten years later, while studying for my commercial radio license I earned my Amateur Extra and received my current call, KU7Q. My love of radio paved the way for a career as a communication tech, engineering assistant, and finally a communications operations and maintenance manager. This project was inspired by the radio control systems I worked on as a tech. Our dispatch console gave our dispatchers access to over 150 base stations in our service area. I always thought it would be nice to have something like that to combine all of my radios into one system so I could easily choose the radio I wanted to use without having to move the mic, headphone, key, PTT, and antenna connections.

Now retired I have the time to pursue my vision of the ideal radio control system.

CTR2 did not start out as an Internet based remote radio control system. It seems like everyone is offering this now days. I recently found Node-RED and created a set of “flows” that mimic the touchscreen display I originally designed the system. My Node-RED flows allow Internet access to the CTR2 HMI using any supported browser. When coupled with an audio transport app such as SonoBus, CTR2 provides a full-featured, Internet enabled, station control system that you can expand by adding flows from other users.

CTR2 grew out of another project I designed back in 2001 called Control the Radio, or CTR. It was a program developed for a predecessor to the current smartphones, the Microsoft Pocket PC. I designed a Bluetooth(tm) interface called BlueLync that plugged into a radio’s CAT connector and allowed you to control that radio remotely with the Pocket PC. If you equipped each of your radios with a BlueLync interface you could control any of them from a single Pocket PC. ARRL published an article on BlueLync and CTR in the February 2007 issue of QST. ARRL members can find that article here by searching for my call, KU7Q. You can also view the archived web site for CTR here.

The original CTR software had many limitations and Bluetooth was cumbersome to use. You had to pair the devices, connect/disconnect the link, and select the correct CAT protocol and baud for the new radio when you wanted to change radios. CTR didn’t support audio to or from the radio so it had no DSP capabilities. It also didn’t save the settings and frequency lists for each radio. However, I really liked the common user interface it provided… every radio looked and worked the same.

CTR2 expands on the original CTR concept with several additions. First, it is self-contained. No external computers or smartphones are required, although they can be used if desired. Second, wired connections are used to and from each radio. While this might seem ‘old school’ it’s actually the best way to manage multiple radios. Wired connections allow easier interfacing to the radio’s audio, CAT, and control circuits. DSP techniques have been applied to both transmit and receive audio. Finally, each radio port has it’s own configuration. Levels, band registers, favorite frequencies, transmit buffers, antenna settings, etc. follow the selected port. I’ve set a practical limit of controlling 16 radios which is more than most hams will ever need.

A functional diagram of a large system is shown below to help you visualize what’s going on.

The main CTR2 unit contains the main controller board (HMI) and the optional switch boards. The physical height depends on the options you install. In the example above the main unit is approximately 4″W x 4″D x 7″H. It can be located in any convenient location in your shack. The remote display is 5″W x 3.5″D x 2.5″H so it’s very easy to find a location for it on your desk. In place of the display Node-RED can be used to manage the HMI.

The diagram above shows the current options supported. Because the system is modular, you can choose which options work for your situation. No option is dependent on another option. Perhaps you have just one radio you would like to control. Use the Auxiliary board with Option 1 (built-in Radio I/O).

Maybe you have two or more radios. The the Auxiliary board with Option 2 and manual RJ45 and antenna switches makes more sense.


Or maybe you don’t want to control any radios. You just want to control a remote antenna switch like a DX Engineering RR8B-HP. Just deploy the HMI and the Antenna Switch Control (ASC) board and use the Antenna Select page to select your antennas. In the future you can add the Auxiliary board as shown below to connect to your radio and give your antenna switch band awareness.

If you’re interested in deploying CTR2 in your station I can supply complete boards for everything shown above. The front, back, and side panels for the main unit shown in the system diagram are optional because they are custom cut for the option boards chosen.

You should understand that the firmware is (and probably always will be) in development (Beta stage). I designed this project as a test bed to experiment with DSP and radio control so while the firmware is complete and functional there are still some minor bugs and I’m always dreaming up new additions to it. I always post the latest versions in this post. The firmware is open source so feel free to modify it to fit your needs.

The lawyers say I have to add this…


CTR2 software and hardware are provided AS IS, without warranty of any kind, either expressed or implied.


I make no warranty that CTR2:

  • will meet your requirements
  • will be secure, bug free, or error free
  • will not damage your equipment
  • quality will meet your expectations

In no event will I be liable or responsible for damages of any kind to yourself, your equipment, or to 3rd parties.

By using CTR2 software and/or hardware you agree to these terms.

I know this sounds pretty unsettling but the reality is that I have very little control over how an end user builds or applies this technology. Although I test every assembled board I can’t guarantee that they will work on your hardware. I have no way to test PCBs with only SMT components. I’ll be happy to help you work out any problems you encounter.

I use CTR2 everyday in my shack to control thousands of dollars worth of equipment and I have never had an equipment problem because of it. I’ve spent a lot time on the design and the implementation to make sure it is as trouble free as I can make it.

Finally, I want this blog to be a positive, learning experience for its users. Before you post a comment here on my forum, remember that everyone is at a different level of expertise and I expect comments from other users to be helpful and supportive towards less experienced users. I’m always open for suggestions and constructive criticism. With that in mind, snarky, rude, belittling, or condescending comments will not be tolerated and will be removed.

I hope you enjoy reading about this project and either build your own or modify it into something that works for you. Even if it just gives you ideas for your next project my effort will be worthwhile.

73s, Lynn, KU7Q

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