CTR2-Mini‘s radio I/O connections are much simpler than CTR2‘s because there is no audio to connect, only CAT, PTT, and Key. This post will provide schematics for the radio’s that I’ve interface to. If you have a different radio, send me your radio’s I/O connections and I’ll generate a schematic for it and post it here.

FlexRadio Series 6000

Let’s start with the simplest radio to connect to, the FlexRadio 6000 Series. This one is simple because you only need to connect Key and PTT to the 15-pin accessory jack on the back of the radio. You can purchase a DE-15M terminal adapter from Amazon for around $10. Wire this to a 3.5mm stereo phone plug and you’re in business. The FlexRadio CAT connection is done over your WiFi network. A special version of CTR2-Mini is available if you don’t need or want to connect Key and PTT to your radio. This version only provides the rotary encoder for frequency control. It makes a great addition to your shack if you’re just looking for physical tuning knobs for one or more slices on your radio. See the Flex-Only option here.

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. I can supply a Flex-only unit with the encoder box, encoder, encoder PCB, knob, Wio GPIO PCB, and acrylic stand in either kit form or fully assembled.

Icom Radios

Most Icom radios have a 13-pin accessory jack on the back of the radio and are supplied with a 13-pin pre-wired plug. You’ll need to use the Red and Orange wires on this plug to connect PTT as shown below. The CI-V and Key connections are done using 3.5mm mono phone plugs.

Icom PCR-1000

The next easiest radio to interface to is the Icom PCR-1000 receiver because it only requires a CAT connection. 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.


All you need to interface to your QCX to the Mini is one stereo 3.5mm cable and one mono 3.5mm cable. Just plug them in as shown below.

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.

Yaesu FTdx101

The FTdx101 is a little more complicated to interface to because of the 6-pin Mini-DIN connector it uses. These can be bought from Mouser, Digikey, or several other part suppliers.

Yaesu FT-8×7

The Yaesu FT-817, FT-857, and FT-897 all use the same interface connections. They use the 6-pin Mini-DIN plug for PTT and an 8-pin Mini-DIN for CAT. A standard 3.5mm mono phone plug connects the Key.

Xiegu G90 and X5105

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

If you want to use the radio’s built-in keyer, select Passthru as the keyer mode in the Mini then use a straight 3.5mm to 3.5mm stereo cable between the radio I/O’s Key/PTT jack and the radio’s Key jack. Passthru passes the left and right paddle inputs directly to the Key and PTT outputs on the radio I/O module. Of course in this mode, remote PTT for voice on the radio is not supported.

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