Probably the hardest thing about setting up CTR2 for station control is connecting your radios to the Radio I/O modules. Every manufacturer has their own way of connecting to the outside world so it will take a little searching and a little trial and error to get the configuration wired correctly.

The lead photo shows a completed Radio I/O module wired for the Yaesu FTdx101D. It requires three connectors, a DB9-Female for the RS232 CAT port, a 3.5mm phone plug for the Key port, and a 6-pin mini-DIN connector for the audio and PTT signals. The 12-pin terminal block is numbered starting at pin 1 on the bottom.

I use a 14-gage copper wire for a strain-relief. Just fold it back on itself and bend the two ends to plug into two of the Ground terminals.

These schematics have been tested on my radios. Each schematic includes a graphic of any special connectors needed, the switch settings for SW1, and the baud rate for the radio. Many radios allow you to change the baud rate. If they do, use the lowest rate if you have a long run (>20 feet) of CAT5 cable to your radio.

Links for the required connectors are at the bottom of this post.


This schematic is the wiring for a Yaesu FTdx101.


This schematic is for the Yaesu FT-8×7 series radios and includes the FT-817, FT-857, and FT-897 models (I think). I use it with my FT-817.


This wiring diagram works with the Flex 6000 Signature Series radios. You’ll note that there is not a CAT serial connection on these radios. Flex doesn’t support full serial CAT control on these radios. You can READ the frequency and mode on the radio’s USB serial port but you can’t WRITE new a frequency or mode to that port. I’ve talked to Flex about this and they have no plans of offering full serial CAT control 🙁

What that means is that in order to have audio, key, PTT, frequency, and mode control of your Flex 6000 series radio you’ll need to wire up the Radio I/O shown below and then connect to your radio using WiFi to control the frequency and mode. It’s an extra step, and quite frankly a pain-in-the-you-know-what. In my station the WiFi signal to CTR2 isn’t as strong as I’d like and the WiFi link to the radio fails intermittently. To be honest, I don’t often use CTR2 with my Flex for that reason. It may just be something I’m doing wrong with the WiFi port. All of my other radios work flawlessly with serial CAT control.


The Xiego G90 and X5105 use the same Radio I/O wiring. The G1M should work with this wiring too. I don’t have one so I haven’t tested it. I have no idea if the new X6100 would be compatible. I can’t see a serial CAT port on it, so it’s probably following Flex Radio’s lead 🙁

Once you wire your radio make sure you enable and set the levels on the radio’s Line In and Line Out functions.


The QCX+ is a small(ish) CW transceiver from QRP Labs. It has a really little brother, the QCX-mini and an older sibling, the original QCX. The interface below works with my QCX-mini and should work with the others.

NOTE: CAT control is an add-on modification for the original QCX and requires a firmware update.


CTR2 includes support for the old Icom PCR-1000 wideband receiver… primarily because I have one and wanted to keep using it 🙂

The Radio I/O is super simple, just connect the speaker to the Line In terminals, install the speaker termination jumper in the Radio I/O module, and connect the serial port to the CAT data terminals. This radio uses the Invert settings on SW1.


Using Other Keyers

You may have an external contest keyer that you want to keep using or maybe you really like the internal keyer on one of your radios and want to keep using it. CTR2 accommodates both of these situations.

To use an external keyer just set CTR2 to use the Straight key in the CW Settings page. Next, connect your external keyer’s output to the Key or PTT jack on the front of the HMI. If using the PTT jack, toggle the Left Function option to switch the left paddle input from Normal to Straight key.

The Left Function option also allows you switch from your paddles connected to the Key input and a straight key connected to the PTT input.

To use your radio’s internal keyer wire the Key output of the Radio I/O module to the Tip and the PTT output to the Ring of a stereo 3.5 phone jack and set the keyer in CTR2‘s CW Settings page to Pass Through. In this mode CTR2 will simply pass through the paddle inputs to the key and PTT outputs of the Radio I/O module.

Connector Links

Here are a few links for the connectors shown above. Your radio may require something else. Google is your friend 🙂

If you’re not comfortable wiring the small connectors, buy the cables instead and use an ohmmeter to determine the pin wired to each lead.

NOTE: I am not recommending the sellers in the links below. These are just examples of where you can buy these connectors. Feel free to search for other sources.

6-pin Mini-DIN connector

6-pin Mini-DIN cable

8-pin Mini-DIN connector

8-pin Mini-DIN cable

DE15 – a 15-pin breakout for the Flex 6xxx

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