December 1, 2023: All CTR2-Micro kits shipped after today will have pre-programmed processors.

CTR2-Micro v1.03.02 firmware is now available. This update includes a new beacon controller mode and a better web server that allows you to control the Micro with most web browsers, including the browser on that old retired cell phone you have stuck in your sock drawer.

The new web interface provides a colorful display for your Micro in addition to providing one touch access to many of the Micro’s and your radio’s controls.

And now, back to the program…

I’m happy announce the newest member of the CTR2 family, CTR2-Micro. The Micro a tiny version of CTR2-Mini. The Micro shares the same DNA as the Mini but is much smaller, less complex, easier to build, and less expensive. The Micro fits in a 60mm x 60mm x 20mm (2-3/8″ x 2-3/8″ x 7/8″) enclosure so it can find a place on even the busiest shack operating desk.

At a starting price of US30 for a complete kit, including CNC cut enclosure and labels, the Micro makes a perfect club build project. Fully assembled and tested Micros are available starting at US47 plus shipping and PayPal fees.

The Micro is small enough to fit next to your keyboard or your paddles. You can even mount it on top of many paddles! You can even mount it on top of a pop can and drop it in your car’s cup holder for a mobile controller.

The Micro includes almost all the features of the Mini. It controls all the radios the Mini can (yes, the Flex 6000 series too). Other features include built-in serial CAT polarity strapping (TTL, RS232, and CI-V), an external DIP switch option, a memory/contest keyer, keyboard keyer, three programmable multi-function buttons (for those buried radio options like panadapter gain), programmable power-up mode, external tuner mode (sets your radio’s mode and Tx power so you can tune your external antenna tuner then restores them on exit), a code practice mode, and a new beacon controller mode.

The Micro is easy to add to your station. Just plug it in to a USB socket on your PC, plug in your paddles, CAT and Key/PTT cables, and tell the Micro what radio you’re running. That’s it!

You love the tuning options the Micro offers including quick tuning digit changes (just press the encoder and turn it), fractional tuning digits (5 Hz, 50 Hz, 500 Hz, etc), zeroing of the digits below the tuning digit (for exact frequencies), RIT, up to 100 favorite frequencies per VFO, a previously visited frequency list, tuning from the favorite list, and range tuning (great for contests and linear satellite transponders), and control over both VFOs on your radio.

Where’s the display?

I intentionally eliminated the display from the Micro. Displays are expensive, difficult to install, and fragile. They also take processor I/O pins which the ESP32-C3 doesn’t have enough of! With no display the Micro is rugged enough to just throw it in your POTA bag and head out.

To configure the Micro you’ll need to connect to its USB serial port with a Telnet terminal, such as Tera Term or Putty. Once connected the Home page will open.

If you’ve used CTR2-Mini this will look pretty familiar to you. Press the encoder or [Enter] on your keyboard to open the menu system. The menu system will also look familiar to you, with a few new options.

Menu navigation is done with the encoder, cursor Up/Down keys, or by pressing the highlighted hotkey on the menu. You can even use your paddles to enter the hotkey.

When running the terminal app on your PC you can just minimize it and only bring it back up when you want to change options. You will have to bring it into focus if you want to use the keyboard keyer option.

Do I need to be tethered to my PC?

A new web server allows you to control the Micro from your tablet or cell phone. Just enter the Micro’s IP address into your browser’s address bar and you can control the Micro with instant access to the pre-programmed functions and CW buffers.

You can power the Micro with a USB phone charger, an OTG cable, or even a USB portable battery.

Can I operate the Micro without a display?

Yes! I designed the Micro so that it can operate as a standalone device. For basic functions like tuning your radio just turn it on and use it. You can set up a Power On mode so that it always starts in a certain mode when it boots. For instance, you can program Power On to start with the keyer speed selected. In this mode, the encoder adjusts the keyer speed on power up so it’s a basic keyer. Or you may want to start it in RIT mode so it’s a dedicated RIT tuning knob on startup.

You can also program the three multi-function buttons to execute functions too. You may want one to open the Tx Power setting, one to open the panadapter gain, and one to open the bandwidth control on your radio.

That’s all well and fine, but kind of boring. What if you want to change bands, or modes, or select a CW buffer to send? Doesn’t that require a display?

Morse to the rescue!

If you know the code (or have the desire to learn it) you can interact with the Micro in code. Just enable the Code Report options you want to use and the Micro will report the frequency and mode, and/or abbreviated menu items in code. If you have a hard time reading your radio’s display (I’m looking at you FT-817), or have sight limitations, this is a great option. You can navigate the menu system and make changes to the Micro’s settings with just the encoder and your paddles.

The report code speed is independent of the keyer speed so your can run the report as fast as you want. This is a wonderful way to increase your code speed and comprehension. Just turn the code report on when you have the terminal or browser connected and you’ll quickly learn the character sequences for each menu. This helps you visualize the characters as you hear them. Then turn off the terminal or browser and operate the Micro without the display. You’ll be surprised at how fast you’ve learned the code. I’ve always had problems getting over 20 wpm because I learned the code by writing it down, and I can’t write faster than about 22 wpm. I’m using 30 wpm on the code report now and catch almost everything. If you miss something, just program one of the multi-function buttons to Report to repeat it.

Works with Flex

As I mentioned above, the Micro works with the Flex 6000 Signature series radios. This opens several opportunities. You can use your Micro as a physical tuning knob while running SmartSDR on your PC. You can also use the network Keying and PTT options so you can key your radio from anywhere. You can add additional Micros and have one for each slice, or use them for dedicated functions.

And yes, the Micro works with the Apple variants of SmartSDR too. Use your tablet or cell phone running SmartSDR and connect the Micro to your radio to add a physical tuning knob. Enable network CW and you have a complete portable CW package.

iOS SmartSDR with CTR2-Micro running split screen on an iPad

Here’s a nice video of Mike, WB6DJI, operating CQWW HF remotely using his iPad and Micro running SmartSDR and the Micro’s web interface in split screen.

Using the Micro Through Your Cell Phone’s Hotspot

Cell phones and services like StarLink use Carrier Grade Network Address Translation (CGNAT). Because of this you can’t forward a VPN connection to your radio through your phone’s hotspot to your home network (i.e. your cell phone can use the VPN but other devices connected to its hotspot can’t).

There is a workaround, albeit an insecure one. Forward port 4992 on your Flex through your home router (i.e. expose it to the internet, yikes!) then use your home router’s outfacing IP address and the IP port to the outfacing port # as the radio’s IP address and IP port on the Micro. Now, connect your Micro to your phone’s hotspot and you can control your radio… but then so can anyone else! Therefore, for security reasons this is not recommended.

I have found a rather interesting workaround for this problem. It may or may not work for your router, but it does on mine.

NOTE: I am not recommending this for others, it just works for me on my router!

  • On the Micro, select the Flex protocol then set the IP address in the CAT Connection menu to your router’s outfacing IP address and in the same menu, set the IP port to the outfacing IP port (the port number that will be assigned to port 4992 when it’s forwarded)
  • On your cell phone, enable its hotspot then VPN into your home router and temporarily ENABLE port forwarding on port 4992.
  • Back on the Micro, connect to your phone’s hotspot. It will automatically connect to your radio and you should be able to control it.
  • Now, go back to your home router on the VPN and DISABLE port forwarding on port 4992. This will block anyone else from accessing this port – and it will remain connected to your Micro! At least it does on my router, you’ll need to verify it on yours.
  • The drawback to this process is that you have to repeat it if you lose the connection.

If you have any other secure solutions that work please let me know.

Order Now!

I currently have a stock of parts and completed units from the second production run for immediate delivery.

You don’t need to pay anything until I have your order ready to ship.

  • PCB with pre-installed SMT devices: $5.00
  • CNC cut enclosure: $7.00
  • Complete kit of parts and a CNC cut enclosure: $30.00
  • Assembled and tested Micro: $47.00

Radio I/O cables, shipping and PayPal fees are additional.

There are two options to choose from for kits and assembled units:

  • OPTION1A: Detent encoder or OPTION1B: no-detent encoder: N/C
  • OPTION2A: Internal jumper header (N/C) or OPTION2B: Exposed DIP switch for CAT polarity ($3.00 extra).

Visit my CTR2-Micro Order page to place your order.


The no-detent (smooth) encoders are nice for tuning but inadvertently bumping them can throw you off frequency. The detent encoder is harder to bump off frequency and works better if you want to use the Micro with the Code Report turned on or with a web browser because you can ‘feel’ each menu selection as you turn the knob.

The internal jumpers are the same as I used on CTR2-Mini and you have to remove the knob and open the case to change them.

The DIP switch is a right-angle mount switch that is accessible without opening the case. This is a great option if you have more than one radio you want to use the Micro with.

The CTR2-Micro Operations Manual can be viewed or downloaded here. You also might want to look at the CTR2-Micro Assembly Manual if you’re thinking of building the kit.

You can download the latest firmware for you Micro here.

As always, I’m interested in your thoughts on my projects. You can use the contact form for here or email me. My address is good on

73, Lynn, KU7Q