Low power carrier plug for the Kenwood TS-570

Although the Kenwood TS-570 shortwave transceiver has a built-in tuner, it tunes virtually no bands with my antenna configuration. That’s why I use an ATU-100 based on N7DDC’s design, which I operate remotely near the antenna. This works, but it’s annoying to have to first reduce the output power from 100W to 10W and switch the mode to CW every time I want to tune, in order to transmit a steady, low-power signal for the tuning process. Fortunately, the Kenwood has a connector for an external tuner and an “AT Tune” button to start the tuning process when a tuner is connected to a dedicated port on the back of the unit. After doing some research, I came across the following thread on groups.io: Low power carrier plug for external/remote tuners. It describes how to use a 1,500-ohm resistor to trick the radio into thinking a tuner is connected to it. This allows you to simply press the “AT Tune” button to automatically transmit a 10W carrier signal, which prompts the remote ATU-100 to automatically tune the antenna.

To build such an ATU dummy dongle, you need the following:

• 1x ELP-06V plug housing
• 2x JST SLF-01T-P1.3E contacts (female)
• 1x 1,500 Ohm resistor

The following diagram shows what which pin of the ELP-06V connector does:

All the necessary materials:

The build of this dummy ATU plug is very easy. All you need to do is to solder the resistor to the two metal contacts:

Now all is left is to insert the two contacts into the middle pins of the housing:

For a particularly professional finish, you can apply a little hot glue to the back. When inserted, the plug looks like this: