To compare with transistor ( complete solid - state ) high - frequency linear power amplifier , there are some disadvantages : bad stability and reliability , low efficiency , high cost for operating , huge cabinet , heavy maintenance work load , low security for high - voltage electricity offering , and to ensure the continuance of tv program , the transmitter must be operating with main frame and spare frame 它们与晶体管(全固态)高频线性功率放大器相比,存在着稳定性及可靠性差、效率低、运行费用高、发射机体积大、日常维护工作量大、高压供电不安全、必须采用主机和备机的运行方式来确保电视节目不停播等缺点。