If the COBRA Audio Box is showing no signal value on Control Panel or is showing '---' on the upper display of your 18R2 when checking signal, this may be due to not having a USB drive in your Audio Box USB port.
With firmware version 5.1.X and higher, COBRA has made changes to how the Audio Box accesses the USB drive to enhance the overall performance of the Audio Box.
Due to this change if there is no USB drive in the Audio Box device it will reset to check the USB device about every 3 seconds. This results in the Audio Box not being able to report signal quality to the COBRA 18R2.
To solve this, please insert a USB storage device into the COBRA Audio Box when conducting signal strength tests and operating the COBRA Audio Box.