Modern Vacuum Tubes
Until about a decade ago, you used to be able to jokingly say that you have a computer or a television that still uses vacuum tube technology. Now that there are virtually no CRT (cathode ray tube) computer monitors or TV screens in service (in 1st-world countries, anyway), you can't get away with it. Bummer. I suppose someday when holographic or direct neural imaging is commonplace, late-adopter types (like me) will joke about our computers and TVs still having physical displays.
On of the few remaining realms for vacuum tubes is high power transmitters used in radio and television broadcasting. It is evidently still cheaper and easier to build a tube for some applications than series/paralleling massive groups of solid state devices, particularly at frequencies well below a gigahertz.
Alpha Tubes (RF Concepts) runs a nice full-page advertisement in the ARRL's QST magazine with a line of vacuum tubes that remind me of some of the ones I photographed from the Microwave Museum display at the 2009 International Microwave Symposium (IMS, or MTT-S) show in Boston. The page is reproduced below without bothering to get permission since they will probably not object to the free exposure (tell them you saw it here on RF Cafe, please). If you want to see some old radio equipment up close and personal, find an amateur radio swap meet in your area.
† See my "Tesslor Model R601S Vacuum Tube AM/FM Radio Teardown Report"
†† See my "1941 Crosley 03CB Floor Console Radio Restoration Project"
Posted September 9, 2013
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