A quadrupole antenna has been designed and manufactured,Weight of theantenna is 498 kg. Having added the tuning equipment to the antenna,in room tem-perature and in the air,the Q value is 4.4×103.Resonant frequency of the antenna can be tuned continuously from 47.3 Hz to 60.5 Hz.Each quarter of the antenna issimplified by representing it as a cantinever beam with a rigid body in the free end.We calculate the resonant frequency by simple method of material meehanics insteadof the complicated method of elastic mechanics and obtain a satisfactory result.Several possible mechanical means to adjust the frequency are compared.In addition,we investigate the possibility of using this type of antenna to detect gravitationalwave at lower frequencies.