More than a half century later, traveling-wave-tube amplifiers still dominate satellite communication. That's right—your ultrahigh-definition satellite TV and satellite radio come to you courtesy of vacuum tubes in space.
Of course, there's a huge difference between Telstar's 3.5-watt, 4-gigahertz amplifier and one of the dozens of highly efficient microwave amplifiers on, say, the DirecTV-15 satellite, launched earlier this year. The latest generation of traveling-wave tubes can provide up to 180 W at frequencies up to 22 GHz, with efficiencies approaching 70 percent and rated lifetimes exceeding 15 years. Though their basic function is the same—amplifying RF signals—just about everything else has changed: the design, the testing, the materials, and the fabrication.
...
And now, ongoing research into a new and potentially revolutionary kind of traveling-wave tube—the ultracompact and ultraefficient cold-cathode TWT—looks poised to deliver the first practical device by the end of this decade. These are exciting times for vacuum tubes. Here's why.
No cheating this time--read the article to find out why.
(Score: 2) by mcgrew on Friday November 27 2015, @11:27PM
I don't know why people don't get that. The same with CDs and MP3s, "digital sound". There's no such thing, all sound is analog. The only thing digital about it is the way the analog signal is stored.
mcgrewbooks.com mcgrew.info nooze.org