Without a doubt, the most frequent question I get when I put anything on social media about CTR2-Mini or CTR2-Mini+ is What’s a CTR2-Mini?.

The short answer is “What do you want it to be?

This blog is dedicated to describing what CTR2-Mini is (“Mini” for short), but I’ve realized (thanks to several commenters) that I really need one page, a “marketing page” if you will, that just tells you what a Mini is and why you might want one. So here goes…

So, what does it do?

If any of the following applies to you, you might want to consider a Mini…

  • you’re the kind of operator that loves technology and is always looking for new ways to apply it
  • you are contemplating purchasing a dedicated remote VFO knob or external keyer for your radio
  • you would like to instantly return to the frequency (or maybe several frequencies before) that you just tuned away from
  • you would like to ’round off’ the lower frequency digits so you can tune to the exact frequency
  • you have multiple radios and would like a common user interface for all of them or would like to share your expensive key, microphones, and headset with all of them
  • you’re tired of digging through menus on your radio just to change an often used setting and would like to assign that setting to a function button for one touch access
  • you would like a dashboard for your radio that displays and controls your radios common settings in real-time
  • you have an external tuner are are tired of doing the change mode->change power->key radio->tune tuner->unkey radio->change power->change mode dance every time you move your frequency
  • you would like a remote meter display so can see the radio’s S-meter, power out, SWR, ALC, and compression levels all the time
  • your radios are more than an arm reach away from your operating position
  • you don’t want to have to boot your PC and run SmartSDR just to check band conditions or operate a sked with your Flex radio
  • you have a Flex radio and would like a small panadapter display in another room in your house (or anywhere else for that matter) to monitor band activity or would like a dedicated tuning knob for multiple slices
  • you’d like to just ‘set and forget’ the radio configuration in WSJT-X or your logging program when operating different radios
  • you’d like to operate your radio from another location in your home or anywhere else
  • You would like to configure your station for SO2R operation or experiment with true receiver diversity
  • you’re like me, and you think it’s cool to be able to build a device yourself that interfaces to some of the most advanced electronics in the world and actually adds to your operating enjoyment

If any of these strike a cord with you, read on!

In the beginning was CTR

The Mini+ is the forth generation of radio controllers that I’ve designed and built. CTR stands for Control The Radio. The Mini+ traces it’s linage back to the original CTR Windows Pocket PC program I wrote back in 2001. I designed a companion Bluetooth interface for CTR called CTR-BlueLync that allowed you to control your radio with your Pocket PC over a Bluetooth link. The project was published in the February 2007 issue of QST. I still have a copy of the original CTR website online, you can view it here.

CTR and CTR-BlueLync

then came CTR2

Fast-forward 18 years when I decided I wanted a knob for my Flex 6400 transceiver. I had just retired and the pandemic was starting so I had a lot of free time. I started working on CTR2, CTR‘s sibling on steroids. The “2” in CTR2 stands for “too” or “also” because in addition to radio control it evolved into a complete multi-radio station control system that didn’t just offer rig control but a contest memory keyer, DSP audio signal processing, FFT frequency display, CW and RTTY decoding, touchscreen with touch tuning, buttons, an optional Node-RED interface, and automatic rig and antenna signal routing. It quickly grew into an oversized shack control system that was very expensive and hard to build.

CTR2 Board Stack and CTR2 Touchscreen Console

QEX featured it in the Sept/Oct 2021 and Jan/Feb 2022 issues. I’ve kept the CTR2 blog posts here for posterity. They make excellent reading for chronic insomniacs 🙂

I discontinued work on CTR2 when global supply chain issues made it impossible to source the parts needed to build it. And honestly, because of the cost, there was very little interest in it anyway.

and next, CTR2-Mini

I started working on CTR2-Mini in Dec. 2021. The goal was to return to the original concept of a control knob for my Flex 6400 (and any of the other radio I own) by removing as much bloat from CTR2 as possible. This made it easier and cheaper to build.

I chose the Wio Terminal from Seeed Studios as the controller/display for this project. It’s a great little development system.

The Mini was featured in an article in the September 2022 issue of QST.

The original CTR2-Mini

and now, CTR2-Mini+

The original Mini did almost everything I had envisioned but there were some compromises.

  • First, it was powered through the USB-C connector on the bottom of the Wio Terminal so you either plugged it into your PC or into a phone charger to use it. Powering from 12 VDC would be better.
    NOTE: The original Mini can be powered from the CTR2-Mini Audio Controller or CTR2-Mini SO2R Controller without using the Wio’s USB connector.
  • Second, while it had a sidetone for CW practice and remote radio operation the volume was low and there was no volume control. More volume and a volume control would be nice.
  • Third, the Mini requires an external Radio I/O module to interface with any radio. While this is nice if you have more than one radio or want to manage audio too, it’s a nuisance if you only want to control one radio. A built-in radio I/O circuit would be handy.
  • Finally, new features have been added to the program that make the optional keypad on the Mini almost a necessity.

By the time the QST article on the Mini was published I was busy creating CTR2-Mini+.

CTR2-Mini+ with radio interface cables

Both the Mini and the Mini+ use the same firmware and operate the same. The Mini+ remedies the issues listed above. You can read more about the Mini+ here. The original Mini is still available on special order. Contact me if you’re interested in one.

So what does CTR2-Mini+ do?

I’m glad you asked!

The Mini+ is the cornerstone of the CTR2-Mini ecosystem. You can start with just the Mini+ for basic radio control and then easily expand your system to add multiple radios and share you keys, PTT switch, multiple microphones, and a headset with them all. You can even add SO2R operation and automatic antenna routing. This page will explain the options available.

CTR2-Mini+ and one radio

Radio Control

At its heart the Mini is a compact, standalone radio controller that you can put anywhere on your operating desk. It’s especially handy if your radio is not located directly in front of you. In my shack the keyboard and monitor get that sweet spot and there’s no room for a radio on my desk. So I put the Mini next to my key and keyboard and locate my radios on shelves, other tables, or the floor (sorry Flex, but you have no knobs!)

The Mini interfaces to the radio’s serial CAT (Computer Aided Transceiver) port. For most radios built from the 1980’s to around 2015 the CAT port was a proprietary serial port using one of three standards, normal TTL levels, RS-232 levels, or the Icom CI-V two-wire bus. The Mini supports all of these standards.

The three major manufactures, Icom, Kenwood, and Yaesu developed their own CAT control protocols. Not to be out done, in the early years Yaesu modified their protocol for almost every new model. They finally settled on a modified version of the Kenwood protocol for their FTdx line (thank you!). Other manufactures adopted either the Icom or Kenwood protocols for their radios. The Mini supports most versions of the ‘big three’ protocols. It also supports the Icom PCR1000 wideband receiver.

Every manufacturer used a different jack or socket for their CAT port. The easiest to interface to is Icom’s CI-V, a mono 1/8″ phone jack. Arguably the worst is the Yaesu FT-8×7 models with that awful 8-pin mini-DIN connector. I can supply adapter cables that adapt the Mini to most radio CAT, PTT, and Key interfaces. I also provide links to the raw commercial cables so you can buy them from the vendors directly. Some will required slight modifications, like replacing a mono plug with a stereo plug, or wiring a stereo jack to the accessory plug for your radio.

NOTE: Starting around 2015 manufactures started converting CAT ports from a serial port to a USB port. Most of the smart manufacturers continue to support the serial port in addition to USB, but some, I’m looking at you Icom and Xiegu, have chosen to go with only a USB port on some of their radios. At the current time the Mini doesn’t support USB CAT ports due to the insane complexity of creating a USB Host port to interface to a radio’s USB serial port. However, this is on my road map and I hope to have a solution sometime in the future.

The Mini also has the ability to interface to any radio using an IP network connection. Some of the recent radios like the Elecraft K4 offer built-in network CAT control. Others support Hamlib rigctld. You can add an inexpensive serial terminal server interface or run serial terminal server software on your PC to put any radio on the network.

One of the things you’ll really appreciate about tuning your radio with a Mini is the variable frequency step resolution. Press and hold the encoder then turn it left or right to increase or decrease the tuning step. Available steps include 1, 5, 10, 50, 100, 500, 1K, 5k, 10k, 50k, 100k, 500k, 1m, 5m, 10m, 50m, and 100m. Using these steps you can easily move around the band or the spectrum quickly. No more spinning the radio’s dial endlessly to move to the other end of the band.

In addition, if the Zero Digits mode is enabled, the Mini automatically zeros the digits below the tuning digit allowing you to easily tune the exact frequency you want.

How many times have you tuned away from a frequency then wanted to go back to it? Of course the Mini offers band stacking registers so selecting a band automatically returns you to the last frequency and mode you were using on that band. But the Mini goes one better. It remembers the last 13 frequencies you stopped on (for longer than 10 seconds) and presents them on the Previous Freq/Mode menu so you can easily return to any frequency and mode, on any band. This list is stored on the SD so it’s always available even after a power cycle.

Contest Keyer and Code Practice

As expected, the Mini also includes a keyer. But not just any keyer. The Mini’s keyer features classic Iambic-A and Iambic-B modes in addition to Ultimatic and Bug modes. A special mode called Passthru simply takes the Dit and Dah inputs from the paddle connected to the Mini and passes them through to the Key and PTT outputs on the Mini. This allows you to connect the PTT/Key Out jack on the Mini directly to your radios’ Key input (or your favorite external keyer) using a 1/8″ stereo cable. If your radio’s CAT protocol supports it, the Mini automatically sets your radio’s keyer speed when you adjust the Mini’s keyer speed so you can use your radio’s keyer and control its speed with the Mini.

The Mini also allows you to connect a straight key to it’s PTT/K Input jack and use it at the same time you’re using your paddles. On SSB this straight key can be used as a remote PTT switch if you prefer.

The keyer features 14 message buffers that can be assigned to function buttons on the unit. For contesters it allows you to assign your call sign, auto-incrementing contact serial #, and contest exchange to prosigns (^, #, and %). This allows you to create a contest exchange in one of the message buffers. A special prosign, *, allows you to temporarily increase you sending speed 50%. This is useful for sending the customary 599 signal report during a contest exchange. Entering *599* into the buffer sends just the report faster. Buffer #1 is assigned as a repeat buffer. The last message sent is saved in this buffer. Assigning this buffer to a function key allows you to repeat a contest exchange with a single button press without incrementing the serial #.

The Mini also provides a keyboard keyer. Just connect the USB-C port on the Mini to your PC and connect a terminal program like Putty or Tera Term to the Mini’s virtual serial port. While in this mode just type in the terminal then press [Enter] to key out your text. You can also control everything on the Mini with the keyboard meaning you can control your radio from your keyboard. Press just the [Enter] key alone to enter Mini Menu mode.

As we’ll see in a minute, the architecture of the Mini system allows you to share your paddles and its keyer with every radio in your shack.

The code practice feature provides a code practice generator for those wishing to learn or upgrade their code proficiency. The practice trainer is based on the Koch method of learning code. The minimum speed of the trainer is 15 wpm. This prevents you from learning code by visualizing the individual Dits and Dahs. You learn the code by how each character sounds. There are plenty of web pages that describe how to use this method so I won’t go it it here.

Radio Dashboard

The Radio menu presents a dashboard of the common settings in your radio. You can open this menu and just leave it open if you find yourself always changing certain properties on your radio (volume, bandwidth, RF gain and attenuation, etc.) In addition, many radio controls can be assigned to the function buttons for instant access to the settings you use the most.

Remote Meter Panel

The Mini can also be used as a remote metering panel. Just select Meter Mode from the Mode menu and the display changes to display five meters, the S-meter, Tx Power Output, SWR, Compression, and ALC levels. This mode is ‘sticky’, i.e. it stays on once you enable it, even through power cycles. So you can just leave the Mini in this mode until you want to use it. Turning the encoder slightly will temporarily return to the Home page where you can tune your radio, change modes, or do other housekeeping tasks. After 10 seconds of inactivity the Mini reverts back to Meter mode. Press the [C] button (Esc) to exit Meter mode and return to normal operations.

The two screenshots below show the Meter page in receive mode on the left and transmit mode on the right.

External Tuner Mode

If you’re like many hams you have an external tuner because your radio’s built-in tuner just doesn’t cover a broad enough range. And, if you’re like most hams, you probably cuss when you have to change your mode setting and reduce power every time you need to peak up your tuner, only to reverse the process to operate.

The Mini eliminates this frustration with it’s External Tuner Mode. When you enter this mode (from the Mode menu) the Mini automatically changes your radio’s mode to CW and reduces the output power to a setting you choose. In addition, the [B] button becomes a latching Key Out control. Just press it once to key the radio and press it again to unkey. If this weren’t enough, the PTT switch on the function keypad or a remote PTT switch become momentary Key Out controls. Just press any of these buttons to generate a tuning carrier. You can instantly change your output power by turning the encoder. When you’re done tuning just press the Esc button (button C) to return to the original mode and power settings. It couldn’t be easier! Here’s a photo of External Tuner Mode in active key out mode.

One Mini, Multiple Radios

As mentioned above, the Mini was designed to expand beyond controlling one radio. It can store radio profiles for up to 16 different radios. Each radio profile contains a favorite frequency list, 14 CW message buffers, the CAT protocol, keyer settings, and other custom settings for that radio. You can use a simple manual RJ45 switch to select which radio to connect the Mini’s RJ45 port to as shown below. You can use multiple profiles with the same radio if you have a lot of frequencies you need to remember, or CW message buffers for different contests or operations.

To select a radio just select its Radio Port on the Mini, select the port on the manual switch, and you’re controlling that radio. The Mini’s keyer, PTT Out, and Key Out automatically connect to that radio. The diagram below shows an example of controlling four radios.

One Mini with manual radio I/O routing

A new automatic port switch, the CTR2-Mini I/O Multiplexer, is now available. This unit replaces the manual RJ45 switch shown below and automatically routes the I/O signals from the selected radio when you select that port in the Mini. Other new products will also join the CTR2-Mini ecosystem in the near future bringing new features, including audio management, to the system. These new products are introduced in this post.

One Mini with automatic radio I/O and antenna routing

Sharing Two Mics and Headsets

If you’re a phone op you’re wondering, “What about Tx and Rx audio”. The Mini covers that too. You can share up to two microphones and a headset in addition to sharing paddles, straight keys, and PTT switches by just adding a CTR2-Mini Audio Controller and replacing the Radio I/O modules with Audio I/O modules as shown in the next drawing. The Audio Controller also has an audio port to connect the selected radio’s Tx and Rx audio to your PC sound card for digital modes.

Third-Party Apps

About now you’re probably wondering if the Mini is compatible with third-party apps like log books and WSJT-X. Yes it is. Just connect the Wio Terminal’s USB-C port (on the Mini) to your PC, connect your third-party app to the virtual serial port created for the Wio, then tell your program it’s talking to a Kenwood TS-2000. That’s it. The Mini will translate the Kenwood commands from the app to the protocol of whatever radio the Mini is connected to. You’ll still be able to control your radio using the Mini. If you switch to another radio your app won’t even know it.

This isn’t a full TS-2000 emulation, just frequency and mode, but that’s usually all the loggers and digital programs control anyway. If you’re running a full featured radio control app you’ll probably just want to stick with that.

Flex Control

As I mentioned previously, my primary driver for creating the Mini was to provide a physical tuning knob for my Flex 6400. The Mini uses WiFi and the Flex IP API to control your Flex over your network. It connects as either a GUI or non-GUI client. In addition, the Mini has enhanced Flex support that allows you to control many of the functions of the radio like Tx/Rx antennas, slice volume, bandwidth, filters, RF gain, Tx power, Tune power, and antenna tuner so you can operate your Flex in POR (Plain Old Radio) mode without SmartSDR running. The Mini even includes a mini-panadapter that’s available when the Mini is connected in GUI client mode. This panadapter, while not as robust and pretty as the SmartSDR panadapter gives you a sense of what’s happening on the band. Imagine having a Mini placed somewhere else in you home just to monitor band activity on the mini-panadapter.

Radio settings can be assigned to the function keys allowing you instant access to the settings you change most. If that’s not enough, the Mini supports real CW and PTT over the network. Just take your Mini and a set of paddles with you and use SmartSDR on your iPad or connect your cell phone to an audio server like SonoBus or Mumble to handle the audio.

And yes, you can connect more than one Mini to your Flex at the same time, even on radios running v2.xx firmware. Assign each Mini to a different slice to get a physical knob and all the Flex features the Mini offers on each slice at the same time, including the link features described below.

If you’re just looking for a physical knob for your Flex without the keyer/sidetone and serial radio CAT features of the full Mini you can add just an encoder and a function keypad to a Wio Terminal. Visit the FlexRadio Features page for the schematic.

WiFi, Bluetooth, and Link Modes

The Mini supports both WiFi and Bluetooth connectivity to support several link modes. Link modes allow two Minis, connected to two radios with the CTR2-Mini SO2R Controller, to synchronize settings. In link mode one Mini is assigned as a server (Mini-A) and the other is assigned as a client (Mini-B).

Basic Link Mode

In Basic Link mode the Tx Enable mode and keyer settings are shared. This means that enabling the transmitter on one Mini automatically disables the transmitter on the other. Changing the keyer speed on one Mini changes it on the other. You can also push or pull the frequency and mode from one Mini/Radio to the other.

Basic + Frequency Link Mode

Basic+Freq link mode includes the Basic Link features plus the frequency and the mode of the two radios are synchronized. This allows you to use two separate radios on separate antennas as a full diversity receiver/transmitter. Just choose the receiver with the best signal when working a station that’s fading, or instantly start using the other transmitter if the main transmitter fails during a contest.

Basic + Tracking Link Mode

Similar to Basic+Freq link mode, Basic+Tracking link mode synchronizes the frequencies of the two Minis and their radios, but offset by their original (before sync mode was enabled) frequency spacing. For example, tune Mini-A to 14.1 MHz and Mini-B to 21.1 MHz then enable Basic+Tracking link mode. Now, tuning either Mini, or either radio will cause the other Mini and it’s radio to move the same distance. So if you tune Mini-A in this example to 14.15 MHz its radio will move to 14.15 MHz and Mini-B and its radio will move to 21.15 MHz. This is useful during a contest if you want to monitor the activity on two bands at the same time. To initiate a contact just enable the transmitter on the Mini you want to use and make the contact. The CTR-Mini SO2R Controller provides the hardware to make this work seamlessly.

Remote Control Mode

In this mode Mini-B is in the shack, connected to your radio and Mini-A is the traveler. It connects to Mini-B over the network (local or Internet) and controls Mini-B remotely, just as if you were in the shack.

SO2R Operation

The Mini’s linking modes also support SO2R (Single Operator Two Radios) operation. In this mode two Minis control two separate radios but the mic/headset, paddles, PTT switch, and straight key are shared. A single press of a button switches you between the radios. The SO2R controller supports two microphone inputs, separate Tx and Rx level adjustments for each radio. A unique switching arrangement allows you to listen to each radio in separate headset speakers, listen to just one radio in both speakers, or combine the audio from both radios and listen to them in both speakers.

And if that isn’t enough…

By now I hope you’re thinking, “Wow, that’s a lot of functionality in a small controller”. But there’s more.

The CTR2-Mini Antenna Switch Controller is a small controller also based on the Wio Terminal. Depending on the model it controls single or dual port remote antenna switches. It’s main advantage is that it can be linked to one or two Minis. This allows the switch controller to be placed out of the way and controlled by the Mini. You also have the option of having the antenna switch controller automatically switch antennas when you switch bands on the Mini.

I’m continually looking for new concepts and operating modes that can be added to the CTR2-Mini ecosystem. An example of the latest developments can be found here.

Build it yourself

The Mini is designed such that anyone with moderate soldering skills can build the unit in a couple of hours. If you can solder .1″ pin headers and RJ45 jacks to a PCB you probably won’t have any problem building the Mini+. To see what’s involved with building a Mini+ download the Mini+ assembly manual.

I can supply PCBs and pre-cut enclosures for either CTR2-Mini or CTR2-Mini+. All PCBs have the SMT devices preinstalled by the factory. You just need to add the through-hole components and connectors. I don’t sell complete part kits. Instead, you can purchase the components you need to complete my PCB kits from my Mouser Mini+ Bill-of-Material page.

I can also supply fully assembled, programmed, and tested units and radio interface cables if you don’t want to build your own.

Wrapping it up

I hope this answers the question, “What’s a CTR2-Mini?“. There’s a lot more information in the CTR2-Mini Overview post. If you’re interested in seeing the user interface in action I have several YouTube videos on my channel (highly rated for insomniacs :). You can also download the CTR2-Mini Operation Manual for an in depth look at the user interface. I plan on adding more videos in the near future to showcase the latest software changes and the new Mini+.

Is that it?

That about covers the Mini, as it is today. This is a constantly evolving project. As new options or modes are suggested by users, or just percolate up from my subconscious, I add them. That’s part of the fun of being the developer… developing. I have a few things on my road map including getting a USB Host port to work for USB CAT only radios and maybe adding other protocols like TCI. I’m sure other things will pop up too. If you have an idea, throw it at me! The nice thing about the Wio Terminal is how easy it is to update the firmware. Just download the new firmware and copy it to the Wio. That’s it. No compiling, libraries, IDEs, or any of that stuff. Just copy and paste a file.

Thanks for checking out my projects. If you have any questions or comments please let me know. You can also contact me directly or via email. You can find my email address on QRZ.com.

73, Lynn, KU7Q