. >> host: why do you only save rudy gigahertz is useful for siler technology?> guest: all that is useful for technology in general. when you go up above three gigahertz or so, all of a sudden you run into a few problems like rain interferes in the antennas get to be tiny and small and pretty soon it's very hard to get energy to go through the air. the useful part of the radio spectrum just in my lifetime has increased considerably. and when i started to work in 1954, we were using 150 megahertz as the highest frequency for voice communications. and little by little we learned how to do better. and by the time we got to cellular, we were up to 800 or 900 megahertz and that we have new system coming out, clear wire is coming out with wimax systems at 2.5 gigahertz and it works very well. you go beyond 3.5 gigahertz or so and the physics starts interfering. so there is a limit to the frequency range. >> host: for the sake of clarification, we talked about broadcasters. chairman genachowski last week specifically said that broadband plan recommended ruby a voluntar