Designed especially for UHF Commercial Bands, Hi and low VHF Commercial Bands scanning, and as a transmitting antenna on the following frequencies 415MHz 4.5dB gain, 164MHz 2.14dB gain, 73MHz unity gain and 40MHz 1/4 wave, the SCATX is resonant at these frequencies with a SWR < 1.5:1. Note: You should NOT use a spring with this antenna.