The user interface for CTR2 is structured like a web browser. The Home page appears after the startup splash screen. This page displays the basic functions of the system. From here you can navigate to other pages by touching the appropriate control.


In CW, Voice, or RTTY operating mode the first line of the Home page allows you to access and control the Transmit Buffer. There are no buffers for Digital mode.

The UI: Working with the Transmit Buffer blog entry describes the transmit buffer options.


The second line on the Home page displays the last 35 characters in the receive decoder buffer. Status messages are also periodically displayed here. To view the entire 500 character receive buffer touch this line to open the Rx Activity page.


The first button on the left of the third line, R1:A2 in the lead photo is a two part button that controls the radio and antenna selection.

The UI: Radio and Antenna Selection blog post describes these options.


The remaining buttons on the third line of the Home page allow you to post log entries. You can view a summary of your log by touching the Log button on the bottom menu.

Logging features are described in the UI: Logging blog post.


The FFT graph is located in the center of the Home page just below the logging buttons. This graph displays a real-time visual representation of the audio bandpass on the yellow line. It’s range is 0 to 3.2 kHz. If you have filters enabled they will be displayed as violet cursors. Decoder tuning cursors are also displayed in CW and RTTY modes. The tuning cursors are green when no signal is being decoded. They turn red when decoding is active.

You can tune the radio’s frequency by touching a signal on the FFT graph. You can also adjust the low pass filter or notch filter using this graph.

The frequency is displayed directly under the FFT graph. You can change the frequency by touching one of the digits of the frequency.

The rotary encoder is a multi-use device. It’s default function is to tune the frequency. Touching the Freq button on the bottom menu steps through the various other functions of the encoder.

The UI: Frequency Control and UI: The Rotary Encoder blog posts have more information about these features.


There are three level controls to the right of the FFT graph. These control the FFT Gain, Headphone Volume, and Receive Squelch. To adjust these levels simply touch and drag the control’s level. You can also touch one then use the rotary encoder to change its level.

  • FFT Gain controls the amp that drives the FFT graph. Adjust this control to set the radio’s noise level below the first graticule on the graph. Use this control to minimize false decoding when decoding CW or RTTY.
  • Vol controls the radio’s volume at the headphone port.
  • Sq controls the level threshold of the squelch detector.

Normally the Sq control should be set to 0 (unsquelched). You can use this control to mute the receive audio when no signals are being received. The audio unmutes when a louder signal is received. This is opposite of how an FM radio’s squelch circuit works. An FM radio’s squelch unmutes when the channel noise decreases in the presence of a carrier.


The Band Select button is at the left-center of the display. It displays the current band (20 meters in the Home page photo above). Touch this button a navigate to the Band Select page.

More information about this page is in the UI: Band Selection blog post.


Modes are displayed below the Band Select button. CTR2 manages two modes. The top mode button displays the radio’s mode. The bottom mode button displays the operating mode. Touching either of these buttons opens the Modes page.

The radio’s mode is which mode the radio is in, CW, LSB, USB, AM, FM, etc.

The operating mode determines which HMI options are active. For instance, in the CW operating mode, the CW decoder is active. In the Voice mode no decoders are active but the equalizers are available.

The Settings button on the bottom line opens the Settings page for the selected operating mode. Within the Settings page you can configure settings for the inactive modes too.

Visit the UI: Modes and Settings blog post for more information about working with modes and settings.


CTR2 supports 100 favorite frequencies for each radio port. The V>M button saves the current VFO frequency, modes, and levels to memory. M>V opens the frequency list so you can select a frequency from your favorites list. You can also use the < and > buttons next to the FFT graph to step through your favorite frequencies.

Visit the UI: Favorite Frequencies blog entry for more information on managing frequency lists.


The Tx Enable/Disable button in the left-bottom corner enables or disables the HMI‘s transmit feature. In Tx Off mode both the Key and PTT outputs are blocked. This allows you to practice with the CW keyer and play Tx buffers for code practice without keying the radio.

Touching the Tx Enable/Disable button to toggles the Tx enable mode. When Tx is enabled this button will be green in receive mode and red when the transmitter is active (Key or PTT asserted).

Visit UI: Transmit Enable for more information about using this feature.


Global settings for the HMI are done in the Config page. This page is available from any of the mode Settings pages. Here you can set your call sign, set the real-time clock, edit your IP information for the WiFi radio, etc.

From the Config page you can also access the Levels page. This page gives you additional control of the various amplifiers in the audio streams of the HMI. Levels set here are radio port dependent since each radio has unique levels that it operates under.

Visit the UI: Configuration and Levels blog post for more information about these options.


The help feature in CTR2 consists of help pages accessed by touching the Help button on the bottom menu. Once the Help page is open use the navigation buttons to scroll through the information.

More information on the Help feature can be found in the UI: Help blog post.


CTR2 includes limited support the Flex 6000 series radios. This is not a ‘full feature’ implementation, meaning, don’t expect to fully control everything on your Flex. Your PC does a much better job of that!

However, it is possible to operate the Flex radio as a ‘normal’ radio, i.e. without the need of a PC. You will have basic controls, DSP options, and antenna tuner control, and a tuning knob!

A WiFi network is required to control the frequency on the Flex. This requires extra steps to set up and get functioning properly.

More information on Flex interfacing can be found in the UI: Flex Radio Control blog post.


CTR2 also has built-in support for the Icom PCR1000 wide-band receiver…um, because I have one! Unlike Flex radio support, the PCR1000 option provides a full feature implementation of radio control.

More information on this option can be found on the UI: Icom PCR1000 Radio Control blog post.