 In time, problems with sources of electrical noise showed that frequency modulation (FM) was superior for its ability to cope with vehicle ignition and power line noise.The frequency range used by most early radio systems, 25–50 MHz (vhf "low band") is particularly susceptible to the problem of electrical noise.This plus the need for more channels led to the eventual expansion of two-way radio communications into the VHF "high band" (150–174 MHz) and UHF (450–470 MHz).