Unfortunately, it is not possible to adjust the transmit power of the Helix Fi gateway's antenna. However, we do take note of your comment for a feature of this type.
If the purpose of your question is to prevent people from seeing your Wi-Fi network, you can still hide your Wi-Fi network name. Although this does not prevent "WiFi analyzer" type applications from seeing there is a hidden network, it will no longer appear on devices when they scan for available networks.
In the Helix Fi mobile app, select "Connect" then "See network". Press the edit button located in the upper right corner then uncheck the option "Broadcast WiFi Name" then "Apply Changes".
This will not affect your devices already connected. However, such a change will mean that you will need to connect any new device by manually configuring your Wi-Fi network name and password or, by temporarily reactivating this option while you connect your device.
Thank you very much Patrick, my question was for reducing the range, so my cat's GPS would switch from WIFI to it's radio sooner - the Helix signal is so strong her GPS picks it up across the street which is too far away. But I solved the issue by connecting her to an extension with a unique name and unplugging it when she is out so that her Radio connects right away. The product is "Whistle Go".