Sam,I suspect your noise is coming from a cheap USB voltage converter. The Stratux will run on 12 volts or 24 volts or the 5 volts coming from a USB converter. If you connect a + wire from the battery and a - wire to ground, your problem will probably go away. The cheap USB converters that plug into the cigarette lighter receptacle are notorious for emiting RF which the radios pick up as static.
Dick Welsh