CTR2-Mini is designed as a modular system where you choose the functions that are most important to you. Even better, your CTR2-Mini system can be easily expanded as your needs change. Whether you’re looking for a small radio controller with a keyer to bring your radio’s controls closer to your keyboard, or a fully redundant, multiple backup SO2R solution, the CTR2-Mini’s ecosystem can scale to fit your needs.

CTR2-Mini+ – The Basic Building Block

The CTR2-Mini+ is the cornerstone of the Mini ecosystem. It can connect directly to, and control a single radio. It has a built-in memory/contest keyer, offers enhanced tuning methods, displays up to five meters depending on your radio (S-meter, Power, SWR, ALC, and Compression), provides a simple way to tune an external tuner, and manages you favorite frequency lists. A diagram of a simple control system is shown below. Simply connect the necessary Radio Interface Cables to the 3.5mm (1/8″) jacks on the Mini+ and plug them into your radio. The Mini+ includes a built-in CAT circuit that matches the Mini+ to your radio’s CAT port.

Controlling Multiple Radios

If you only have one radio, the basic Mini+ configuration is all you need. When the time comes that you want to control another radio in your shack you’ll quickly find it can be quite a nuisance to switch your mic, key, headset, and antenna between radios. This is where you’ll appreciate the Mini’s selection of options.

The Mini can support up to 16 different radio ports. The profile for each port stores everything the Mini needs to know about the radio on that port. The RJ45 connector on the Mini includes all the signals required to control a radio’s CAT and control the PTT and Key inputs on the radio. These signals must be routed (switched) to the radio you wish to operate, and processed at that radio using one of two I/O module types.

Basic Two Radio Control

A basic two radio control system is shown below. This system only routes CAT, PTT, and Key signals using a manual RJ45 (CAT5) switch and two external I/O modules. You’ll need to manage your microphone and headset connections manually.

You can replace the manual RJ45 switch with the CTR2-Mini I/O Multiplexer shown below. This device automatically routes the I/O signals from your radio to the Mini when you select a radio in the Mini’s Radio Port menu.

It also provides open-collector outputs that can be used to control an external antenna switch providing automatic antenna routing to the selected radio. An optional CTR2-Mini ASR antenna switch relay driver is required if your antenna switch requires +12VDC to activate its antenna relays.

The multiplexer can be daisy-chained to three additional multiplexers allowing a total of 16 radios to be connected in this configuration.

NOTE: The RJ45/CAT5 I/O signals from the Mini+ are not Ethernet. An Ethernet hub or switch WILL NOT work with the Mini.

One of the drawbacks of this configuration is that you will need to manage the microphone and headset connections to the selected radio. The next section shows what is needed to add audio management to the CTR2-Mini system.

Adding Audio

The next configuration is similar to the one shown above. The differences are that a CTR2-Mini Audio Controller has been added between the Mini+ and the Radio I/O modules have been replaced with CTR2-Mini Audio I/O modules. In this configuration 12 VDC is connected to the Audio Controller and it powers the Mini+, I/O Multiplexer, and the Audio I/Os.

The Audio Controller adds transformer isolated Line-In and Line-Out signals to the radio I/O signals from the Mini+. The I/O Multiplexer automatically routes these signals to the Audio I/O module attached to the selected radio. As with the basic system described above, the multiplexer can control a remote antenna switch to route the antenna to the selected radio.

Mixing Radio and Audio I/O Modules

The Radio I/O module and the Audio I/O module use different wiring since the Audio I/O interface also supports Line-In and Line-Out audio. Therefore, you can’t mix and match I/O modules on the same I/O Multiplexer. But what if you have already purchased Radio I/O modules or you have several CW only radios and want to deploy an Audio Controller to add audio to your system? You can mix the two I/O module types by deploying two multiplexers, one ahead of the Audio Controller for the Radio I/O modules and the other after for the Audio I/O modules, as shown in the diagram below. The multiplexer before the audio controller passes just the radio I/O signals from the Mini. The Audio Controller is plugged into the first multiplexer’s Expansion jack. It adds Line-In and Line-Out to the I/O wiring and passes it to the second multiplexer. This is a good example of the flexibility of the CTR2-Mini architecture.

In this configuration the first multiplexer is strapped for Radio Ports 1 to 4 and the second multiplexer is strapped for Radio Ports 5 to 8. The antenna control pins on each multiplexer are wired to the 1×4 antenna switch such that that activate the antenna relay for the selected radio. You could strap the second multiplexer for Radio Ports 1 to 4 and just plug the two radios on this multiplexer into Ports C and D as both multiplexers will respond to the same port switch command from the Mini.

Making the Leap to SO2R

You may have heard about SO2R (Single Operator Two Radios). Many contesters use SO2R during contests to increase their scores. SO2R isn’t just for contests though. I’ve written a blog entry about this called SO2R is Not Just for Contesters Anymore!

Configuring your Mini system to support SO2R is simple. As shown in the drawing below you just need to replace the CTR2-Mini Audio Controller with a CTR2-Mini SO2R Controller and deploy a second CTR2-Mini+. The multiplexer isn’t required in the basic SO2R configuration because the SO2R controller instantly selects the desired radio with the push of a button.

As with the CTR2-Audio Controller, the SO2R Controller is powered by a single 12 VDC supply and supplies power to both Minis and the Audio I/O modules.

This system can be built out to support fully redundant warm-standby radios for serious contesters. I’m sure serious contesters have much better, and higher cost, solutions for their needs. I only present this configuration to show what the modular Mini architecture is capable of. In theory the Mini system can support 16 radios on each multiplexer so this system could support up to 32 radios!