Next, there are two signals that are separate but may share the same sources. One is at 440 MHz and the other is at 445 MHz. We do not know what causes these signals. They might come from radiolocation or fixed mobile communication. Radiolocation means using radio waves to find something. Fixed mobile communication allows both fixed and mobile wireless signals on these frequencies. Fixed wireless means the transmitter and receiver stay in one spot, while mobile wireless means the devices can move around.