how big can a rubee loop antenna be? as the antennas get larger and larger noise becomes the gate keeper. a 100 ft (30 m) diameter loop can detect lightning storms hundreds of miles away. the biggest source of noise is deep space kilometric noise. while it is possible build a second antenna and do differential subtraction, a limit of a rubee network is adequate for most practical visibility applications. rubee antennas may also use ferrite rods with wire coils and get same range but without large loops.