CTR2-Mini is a smaller, less complicated, less expensive alternative to the CTR2 radio HMI. It uses a Seeed Studios Wio Terminal for its processor. Unlike CTR2 with a separate display and HMI, the Wio Terminal is the display and the HMI!

In addition, it’s available in left or right-hand models as shown on the lead photo. It can even be built with the encoder in the center for a slimmer package. They are easy to build or you can order completely assembled units if kit building isn’t your thing.

If you’re a FlexRadio Series 6000 owner you’ll be happy to know that multiple Mini’s can connect to your radio at the same time, with each Mini controlling one of the slices. A recent update allows you to run real CW over the network so you can connect your paddles to your Mini upstairs and run CW on your Flex downstairs (or across the state).

I have several YouTube videos introducing CTR2-Mini. You can view them on my channel. Several enhancements have been made to the Mini since these videos were produced. You can read about these changes here.

Here are some links to a few of them…

It will give you good idea of what CTR2-Mini is all about, and what it can do for you. I am adding new features the Mini almost daily so some of these videos will be out of date. I’ll keep the feature list at the end of this page current.

I’ve also posted a construction video showing you how it all goes together.

For those that have Flex radios, I’ve posted a video that goes over the special FlexRadio features included in the Mini. Multiple Mini’s can be connected to your Flex radio with each controlling their own slice as demonstrated in the video below.

I also have a video that goes over the Mini’s User Interface in detail. It’s a pretty long video (25 minutes) so I’ve included a timeline in the video description so you can skip through it to find things you’re interested in.

I’ll be posting additional videos on the near future that go over other aspects of CTR2-Mini so if you want to be notified when these videos come out subscribe to my channel and click the Bell button.

Built using DNA from CTR2, CTR2-Mini has many of the features built into CTR2 but is missing some of the more expensive features like digital audio management (bridging, routing, etc) and DSP features like filtering, signal demodulation and decoding, and an FFT graphical display. While nice to have, most of these features are built into late model radios. CTR2-Mini also doesn’t support automated switching of radio ports, radio antenna switches, or antenna switches.

So what does it do? Well, for starters, it provides an extremely small user interface with the same radio control and CW keyer features found in CTR2. It’s about the same size as the 3.5″ Nextion display used in CTR2, and the total cost is about the same as that display. It is entirely self-contained. Because of its small form factor it can easily sit anywhere on your desk. Your radios can be placed more than an arm’s reach away as most of the repetitive tasks such as tuning and mode changes can be handled on CTR2-Mini. It manages frequency lists, CW transmit buffers, and band stacking registers for each radio port and it has a shared radio database available to every radio. It can control RIT if your radio’s CAT protocol supports it. The Mini supports the same radio CAT protocols as CTR2 and the new, smaller, cheaper, streamlined Radio I/O mode supports normal and inverted data levels and Icom CI-V just like CTR2. It has the same CW keyer option and it supports contest operations (sequential serial numbers and exchanges).

The radio interconnections are based on CAT 5 cable so it can control up to 16 different radios using manual RJ45 switches like the non-automated versions of CTR2. This is great if you have radios scattered around your shack like me!


The following CTR2 features are supported by CTR2-Mini:

  • Like CTR2, one to 16 radios can be connected to, and controlled by the Mini
    • Each radio port has its own settings, radio CAT protocol, favorite frequency list, band stacking registers, and 14 keyer message buffers
    • A common database of settings can be shared between all radios
    • Any radio profile can be copied to another profile. Just change the radio CAT setting (if needed) and have all the same settings for different radios.
    • A manual RJ45 switch can be used to select from multiple radios as shown in the drawing above, or you can just control one radio. CTR2-Mini will be cheap enough that you can have one on each of your radios.
  • The user interfaces with CTR2-Mini using a small color display and a rotary encoder. It does not have a touchscreen but menu navigation is quick and easy. Settings can be entered using the encoder (scroll for a character at each position), using the paddles to key in the text, or with your PC’s keyboard when you connect to CTR2-Mini with any terminal program. You can also edit files on the micro-SD card on your PC. This really helps if you want to import Internet frequency lists.
  • All radios are controlled using the same user interface (i.e. all radios look the same to the user). To keep the interface consistent a limited number of parameters are controlled via CAT control on most radios (see next bullet item).
  • The value settings window is “sticky”, meaning it doesn’t close once it’s opened. This allows you to open a parameter like RIT or Keyer Speed and leave it open during operation so you can adjust that parameter ‘on the fly’. Many parameters like RIT and Flex volume can be toggled On/Off without leaving the window. For instance, you can open RIT, set your radio where you want it, then short-click the encoder to temporarily turn off RIT for normal operation. Short-click the encoder again to return RIT back to where you were.
  • The Mini supports Icom, Kenwood, and many Yaesu CAT protocols. Other radios based on these protocols can also be controlled. Dedicated menus have been added to provide additional control of the Flex 6000 radio series and the Icom PCR1000 wideband receiver. If your radio isn’t included in the current list let me know. I’d be happy to work with you add your radio to the list.
  • The multi-function rotary encoder natively changes frequency – click it to step through additional setting options using a menu driven user interface. You can also use the 5-way switch on the Wio Terminal in-lieu of the rotary encoder. Encoder tuning is speed sensitive. Spin it fast to increase/decrease the step by a factor of 10.
  • You can assign one function or menu to the [C] button so it can be opened without scrolling through layers of menus. For instance, RIT can be assigned to the [C] button so one button press gives you the RIT adjustment window. The window stays up until you close it. You can even turn it off and back on without leaving the RIT window. Other functions such as PTT and Keyer Speed can be assigned to this button along with various menu such as the Frequency, Mode, Band, VFO, Tx Memory, Edit Tx Memory, WiFi, Theme, Flex, or PCR-1000 menu.
  • CTR2-Mini can be completely controlled from your keyboard when it’s USB serial port is connected to a terminal program on your PC such as Putty or Tera Term. Menus are presented in the terminal window just as they appear on the Mini. Keyboard keying is also supported. Just enter your text and press [Enter] to send. Message buffers can also be sent from the function keys.
  • Frequency control is accomplished using several different methods
    • Like CTR2 the rotary encoder changes the frequency by the selected frequency step (highlighted number in the frequency display). Press and turn the encoder to change the frequency step. Spinning the encoder fast changes the tuning rate by a factor of 10.
    • Keyboard cursor control keys control the frequency and step when a terminal program is connected to the built-in terminal interface on the USB serial port.
    • Select a favorite frequency from a list of 100 frequencies
    • Select from up to 10 of the last frequencies visited (including modes)
    • Receiver Incremental Tuning (called RIT or Clarifier depending on the radio) is supported for many radios.
  • CW operation mode has the following options
    • Like CTR2 the keyer supports straight key, pass-through, Iambic A and B, Ultimatic, and bug modes. Pass-through mode controls the Key and PTT outputs with the left and right paddles. This allows you to use an external keyer or your radio’s built-in keyer if you prefer.
    • Keyer speed is adjustable from 5 to 50 wpm. Farnsworth spacing is also available for the Tx message buffers.
    • A sidetone interface means the keyer can be used for code practice when transmit is disabled. A 3.5mm jack is provided for private practice or for connecting to a larger speaker.
    • When connected to a terminal program such as Putty or Tera Term, CTR2-Mini provides a keyboard keyer.
    • Prosigns can be embedded in message buffers that automatically send your call (^), contest SN (#), or contest exchange (%)
    • Auto-speed changes can be applied to repetitive exchanges such as contest ‘599’ RST reports. Simply bracket the text with asterisks (*) to increase the sending speed 50% for that text.
    • Message buffer #1 always holds the last buffer sent so it’s easy to repeat a contest exchange without incrementing the SN. It’s recommended to use buffer #2 for your contest exchange but you can use any buffer you want.
  • The Remote PTT Input jack provides three options:
    • Normal mode just passes the Remote PTT input signal on to the PTT Output of the radio I/O module. A ground on the Remote PTT Input grounds the PTT Output.
    • Latch mode toggles the PTT Output on the radio I/O module each time the Remote PTT Input is grounded.
    • Key mode passes the Remote PTT Input on the the Key Output of the radio I/O module. This allows you to connect a straight key to the Remote PTT Input and use it along with the Mini’s keyer to key your radio.
  • The [C] button on the Wio Terminal can be used as a latching PTT button in-lieu of using a remote PTT button. Enable Tx first (press the [A] button, then press [C] once to enable PTT and push it again to disable PTT.
  • The USB-C port supports a USB serial port. Use this port for:
    • 3rd party applications to control the selected radio through CTR2-Mini
      • Like CTR2 the USB serial port emulates a Kenwood TS2000 transceiver – commands from your 3rd party application to control CTR2-Mini‘s TS2000 emulation are translated into the appropriate command to control the selected radio. Your 3rd party app can control PTT using Kenwood’s TX CAT command.
    • You can connect to the USB serial port with a terminal program as described above. The terminal interface displays the menus just like your were controlling the Mini locally.
  • CTR2-Mini can connect to your local WiFi network. This is required for Flex Radio CAT control. The Mini’s Flex interface gives you the following features:
    • Connect to any slice on your Flex radio. You can also create new slices and panadapters.
    • Multiple CTR2-Minis can connect to your Flex radio simultaneously. This gives you the ability to have a physical knob and favorite frequency list for each slice. Make a slice active by pressing the [A] button (Tx Enable) on the Mini controlling that slice. Any other Mini’s and their slices will revert to inactive mode.
    • Control the DSP filters and volume on the slice you are controlling.
    • You can change the default IP port from 4992 to any valid port #. This allows you to forward an IP port through your router to your Flex radio and connect the Mini to if from the public Internet. You will probably want to add additional layers of security for this option.
    • You can select either hardware PTT (from the Radio I/O module) or control PTT input from the Flex network API using the ‘xmit’ command. Using the API allows your Mini to control your Flex remotely without the need for SmartLink.
    • You can select either hardware KEY (from the Radio I/O module) or control the KEY input to your radio over the Flex network API. This allows you to connect to your Flex and have a real CW QSO with a Mini in another room (or another state). Use SmartSDR on your iPad or iPhone or an audio server such as SonoBus to pass audio between you and your radio.
  • The Icom PCR-1000 is supported. If you have one of these receivers kicking around CTR2-Mini can bring it back to life at a very reasonable cost.

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