Plasma antennas are radio frequency antennas that use ionized gas instead of metal conducting element of conventional antenna to transmit and receive signals. In this paper, the effect of changing material of the inside coupler on bandwidth, return loss and radiation pattern at Ultra High Frequency (UHF) band is investigated. It is demonstrated that the resonant frequency can be adjusted by choosing proper material for internal coupler without changing the antenna size and structure. The antenna and its coupler is simulated by practical software Computer Simulation Technology (CST) Microwave Studio. Manuscript profile