The device would need a power meter to detect and switch channels, which involves altering the resonance frequency of the antenna, ( I suspect an amperian loop

The device would need a power meter to detect and switch channels, which involves altering the resonance frequency of the antenna, ( I suspect an amperian loop ) http://www.physics.upenn.edu/courses/gladney/phys151/lectures/lecture_mar_07_2003.shtml http://www.physics.upenn.edu/courses/gladney/phys151/lecture...