Sirio Antenna Thunder27 25-29 MHz CB/Ham Base Antenna This antenna works best for RV or apartments, Balcony or temporary installation antenna omnidirectional designed to work without ground plane factory Type: 1/4  helical loaded dipole frequency range: 25-29 MHz impedance: 50 Radiation (H-plane): 360 omnidirectional polarization: Linear vertical gain: 0 dBd, 2.15 dBi bandwidth SWR  2:  5000 kHz SWR res. freq.:  1.5 Max. Power: 100 watts (CW) continuous 300 watts (CW) short time feed system / position: direct / base connector: UHF-female Materials: Aluminum, steel, nylon, copper wind load