CTR2-Mini was designed to be a simple, small radio controller that anybody could easily build and deploy in their station. It’s also designed to be a building block that allows you to build-out a complex SO2R (Single Operator Two Radio) controller system as your needs expand. Multiple operational options are available when linking two Minis via WiFi or Bluetooth LE that just aren’t available any other way.

As shown in the lead photo, two Minis and the CTR2-Mini Antenna Switch Controller (ASC) can be linked together to create a full SO2R control system where each Mini controls its own radio and the station antenna configuration. To make the most of this configuration a CTR2-Mini SO2R Controller can be added.

This post will describe each Link option so you have an idea of what’s available.

Basic Sync

Basic Sync mode allows you to link two Minis and synchronize several functions. Each Mini and its radio operate autonomously but you can easily push or pull the frequency and mode from one Mini/radio to the other Mini/radio. This allows you to use one radio as your operating radio and the other radio as a search radio during a contest, or when you just want to watch another band for an opening.

Basic + Frequency Sync

Basic + Frequency Sync mode provides the same features as Basic Sync mode plus it synchronizes the frequencies of both radios. This gives you full receiver diversity since each receiver listens to the same frequency on a different antenna. Just use the radio/antenna that works best for the station you’re working. In this mode, tuning either Mini or either radio changes the frequency both Minis and radios.

This mode provides a Rx-B Zero Beat adjustment on Mini-B’s Link menu so you can zero out any frequency differences between the two receivers.

Basic + Tracking Sync

This mode is similar to the Basic + Frequency Sync mode with the exception that the two Minis and their radios are tuned to different frequencies. These frequencies are usually on different bands. In this mode, tuning either Mini or its radio tunes the other Mini and its radio the same amount. The frequency offset is determined when you first establish the link. For instance, if Mini-A (and its radio) is tuned to 7.000 MHz and Mini-B (and its radio) is tuned to 14.000 MHz when you connect the link, tuning Mini-A to 7.050 MHz tunes its radio to 7.050 MHz and it tunes Mini-B and its radio to 14.050 MHz.

This allows you to work two bands at the same time during a contest (or even when just casually operating). As you tune one band you automatically tune the other band. Radio-A is connected to your headphone’s left speaker and Radio-B is connected to the right speaker. When you find a station calling CQ just enable the Tx on that Mini and answer their call. Using the CTR2-Mini SO2R Controller greatly simplifies this because it allows you to mute the other radio or even combine both radios into a mono headphone signal.

Remote Control

This mode is more conventional than the first three modes. In this mode, Mini-B is connected to the local radio and Mini-A is linked to Mini-B via WiFi as a remote controller. This mode allows Mini-A to control your radio remotely from any Internet connection. Audio to and from the radio to the remote location can be handled by an audio server such as Sonobus or Mumble. Direct CW keying is not currently supported in this mode.

Now, let’s add the CTR2-Mini Antenna Switch Controller to the mix…

One Mini and the ASC

Linking one Mini to the ASC allows you to control the antenna selected on the ASC from the Mini. Although the ASC is designed to operate as a standalone antenna switch controller, linking it to the Mini is convenient if you have the ASC located away from your operating position.

Two Minis and the ASC

As shown on the lead photo two Minis and their radios can be linked into a complete SO2R radio controller system. The configuration required to do this is shown below.

Note that Mini-B does not link directly to the ASC. Instead it uses Mini-A as a gateway to send and receive ASC information. In other words, Mini-A is always required if you want to control the ASC with Mini-B.

Another item to note is that ASC control is only done via WiFi. Bluetooth LE is not supported at this time.

SO2R Operation

The full Single Operator Two Radio (SO2R) build out using two Minis, the CTR2-Mini Antenna Switch Controller, and the CTR2-Mini SO2R Controller is shown below. More information on this configuration can be found here.