The energy the georgia tech researchers , including professor manos tentzeris ( above ) , are gathering comes from radio and television transmitters and cellphone and satellite networks .
Dr zaitsev has access to one of the world 's most powerful radio transmitters , the evpatoria , and he has already sent a number of " hello " signals to nearby star systems .
In 2008 the fcc voted to reallocate the various segments of white space and unused channels between 54mhz and 806mhz ( channels two to 69 ) , which would no longer be needed when the last of the country 's analogue television transmitters switched to digital broadcasting in june 2009 .
Or they use low-power transmitters heard only on school grounds .
或者他们使用只在学校场地上听得到的低功率发射机。
He thought about his early days in radio , working around high-powered transmitters .
他回想起早年做无线电工作时,守在高能量发射机旁工作的那些日子。
The last of the big television stations still broadcasting in analogue will turn off their transmitters and begin digital transmissions only .
最后一批仍以模拟方式进行广播的大电视台,将关闭它们的发射机,开始只传送数字信号。
Only a few countries can carry out dazzle attacks , but dozens of countries can jam satellite signals using ground-based transmitters to overwhelm their signals .