Let’s talk about the elephant in the room. Every radio controller has one issue that’s a pain in the you know what, and that’s interfacing it to your radio. CTR2-Mini is no exception. Every radio manufacturer has their own unique way of interfacing their CAT and PTT signals to the outside world. Luckily every radio I’ve ever used provides a 1/4″ or 1/8″ mono or stereo jack for Key input.

For this project I chose to use two 1/8″ stereo phone jacks on the Mini’s Radio I/O module. These jacks are labeled ‘C’ for CAT and ‘K’ for Key and PTT. The ‘K’ jack has Key wired to the Tip of the jack and PTT wired to the Ring. Both signals use the Sleeve for ground.

The easiest way to breakout the Key and PTT signals on the ‘K’ connectors is to use an 1/8″ stereo to dual 1/8″ mono phone adapter such as this one on Amazon. Just cut off the RED plug that’s wired to the Ring terminal on the stereo plug and add the connector you need for PTT on your radio to that lead. There are also 1/8″ stereo to dual 1/4″ mono phone adapters if you need a 1/4″ plug for your radio’s Key input instead.

NOTE: After a lot of testing I’ve decided that many radio’s won’t work when using a mono plug in their Key Input jack. Before you build your Key/PTT cable, test your radio by plugging an unterminated mono cable into your radio’s Key Input jack. If your radio keys up just order a 1/8″ stereo plug and replace the WHITE mono plug on the dual mono adapter with the stereo plug, leaving the Ring terminal open. I’ve updated the drawings below to show this plug.

You can choose to not use the PTT functions of the Mini (i.e. remote PTT switch, using the [C] button or function keypad for PTT, 3rd party application CAT control of PTT, or the latching PTT feature) and simply connect the ‘K’ jack to your radio’s Key input using an 1/8″ stereo phone cable. Make sure you use a shielded cable.

Shielded 1/8″ stereo phone cable can be used to connect the Mini’s CAT (‘C’) port directly to the CAT on some radios (QRP-Labs QCX, all Icom CI-V, and Xiego G90/x5105 for example). Make sure you order a shielded cable with 1/8″ stereo plugs on each end and stay away from the ‘super flexible’ ones as they use tiny enamel coated wires that are hard to work with and probably aren’t shielded (the ones I tried weren’t). If you need to interface to a different connector on your radio’s CAT port simply cut the plug off one end of the cable and add the required connector shown in the drawing for your radio.

If your radio isn’t shown below it’s because I don’t have one 🙂 Send me your radio’s I/O connections and I’ll generate a schematic for it and post it here. I can also build a limited number of interface cables if you really can’t build them yourself. You can contact me for a price quote.


QRP-Labs QCX

Let’s start with the easiest radio to interface to, the QRP-Labs QCX. This radio only requires one 1/8″ (3.5mm) stereo phone cable and one 1/8″ mono phone cable. Just plug them in as shown below.

Select the Kenwood1 on the Config->Radio CAT menu and select 38.4 kBaud on the Config->Radio Baud menu. Close switches 1, 2, and 3 and open switches 4, 5, 6, 7, and 8 on the Radio I/O module.

NOTE: Because of the simple CAT circuit in the QCX it’s best to plug the CAT and Key connections in before powering the radio up.


Icom Radios

If you don’t need to control PTT with the Mini just use two 1/8″ (3.5mm) mono phone cables to connect the Icom’s CI-V CAT and Key to the Mini’s Radio I/O module. If you want to use the PTT functions of the Mini (remote PTT switch, PTT latch), wire the Red and Orange leads on the 13-pin accessory pig-tail that came with the radio to the Ring and Sleeve of the Radio I/O module’s Key/PTT jack. This is easily done by using an 1/8″ stereo to dual 1/8″ mono adapter such as this one.

Select the Icom in the Mini’s Config->Radio CAT menu. The baud defaults to 19.2 kBaud. Close switches 1, 2, 3, and 8 and open switches 4, 5, 6, and 7 on the Radio I/O module.


FlexRadio Series 6000

The FlexRadio 6000 Series is another easy radio to connect to because you only need to wire the Radio I/O module’s Key output (Tip and Sleeve) to a 1/8″ (3.5mm) mono phone cable and the PTT (Ring and Sleeve) to the 15-pin accessory jack on the back of the radio. You can use an 1/8″ (3.5mm) stereo to dual 1/8″ mono adapter and a DE-15M terminal adapter for this cable assembly. You don’t need the 15-pin adapter if you don’t need to control PTT. You can also do away with the Radio I/O all together as the Mini can control the Flex PTT and Key over the WiFi connection.

Select Flex on the Config->Radio CAT menu. Next, in the Mini’s main menu, open the Flex 6000 menu and set the IP address of your Flex radio. The radio’s IP address can be found in SmartSDR on the Settings->Radio Setup…Network tab. Finally, connect the Mini to your local WiFi network to connect to your radio.

Flex-Only Option

You can make your Wio Terminal into a Flex-only controller by wiring a 2-phase encoder to the Wio’s GPIO bus as shown in the diagram below. This is convenient if you just want to use a couple of Minis as physical tuning knobs for your Flex.


Icom PCR1000

The Icom PCR1000 receiver is also easy to connect to the Mini because it only requires a CAT connection. Wire a 1/8″ (3.5mm) stereo phone jack to a DB-9 Male connector as shown below. Make sure you loop pin 7 to 8 on the DB-9 male connector attached to the radio otherwise the radio will shut off a few seconds after you turn it on with the Mini.

Select the PCR1000 in the Config->Radio CAT menu. The baud rate is automatically set to 9600. Open switches 1, 2, 3, and 8 and close switches 4, 5, 6 and 7 on the Radio I/O module.


Yaesu FTdx101

The FTdx101 is a little more complicated to interface to because of the 6-pin Mini-DIN connector it uses for PTT. One 6-pin plug is supplied with the radio. These can also be ordered from Mouser, Digikey, or several other part suppliers.

Select Yaesu FTdx on the Config->Radio CAT menu and set the baud to 4800 in the Config->Radio Baud menu. Next, set the radio’s RS232 CAT port to 4800 baud on the radio’s the Operation Setting->General->232C Rate menu. Open switches 1, 2, 3, and 8 and close switches 4, 5, 6 and 7 on the Radio I/O module.


Yaesu FT-8×7

The Yaesu FT-817, FT-857, and FT-897 all use the same interface connections and are the hardest to interface to. They use a 6-pin Mini-DIN plug for PTT, an 8-pin Mini-DIN for CAT and a 1/8″ (3.5mm) mono phone plug for the Key input.

For the CAT connection use an 8-pin mini-DIN breakout cable such as this one and just install a 1/8″ stereo plug on the wires connected to pins 3, 4, and 5 as shown below. Use heat shrink tubing on the other wires to keep them from shorting together or to ground.

For the PTT connection order a 6-pin mini-DIN male to male Cable for a PS/2 device (similar to this one) and cut one connector off. Next, find the wires connected to pins 2 and 3 of the remaining mini-DIN connector and connect them to the Ring and Sleeve of the Key/PTT stereo plug as shown below.

Select Yaesu FT8x7 on the Config->Radio CAT menu. The baud rate defaults to 38.4 kBaud. Close switches 1, 2, and 3 and open switches 4, 5, 6, 7, and 8 on the Radio I/O module.


Xiegu G90 and X5105

The Xiegu series radios require an 8-pin Mini-DIN plug for the PTT, an 1/8″ (3.5mm) stereo phone plug for the CAT (it plugs into the CAT port on the front panel of the G90), and an 1/8″ mono phone plug for the Key.

You can use a 1/8″ stereo to dual 1/8″ mono cable adapter (such as this one on Amazon) for the Key/PTT connection. Cut off the 1/8″ mono plug wired to the Ring lead of the stereo plug on the adapter cable and connect an 8-pin mini-DIN breakout cable such as this one to that wire as shown below.

Select Icom in the Config->Radio CAT menu. The baud will default to 19.2 kBaud. Close switches 1, 2, and 3 and open switches 4, 5, 6, 7, and 8 on the Radio I/O module.