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  • (Score: 0) by Anonymous Coward on Saturday November 17 2018, @08:03PM (5 children)

    by Anonymous Coward on Saturday November 17 2018, @08:03PM (#763195)

    Vacuum tubes are still used in satellites and musical instruments for amplification.

  • (Score: 2) by VLM on Monday November 19 2018, @12:43PM (4 children)

    by VLM (445) Subscriber Badge on Monday November 19 2018, @12:43PM (#763860)

    satellites

    Traveling wave tubes, yeah. Kinda getting pushed out by solid state amps. Would not be surprised to see the end of TWTs in a decade or so.

    • (Score: 3, Insightful) by RS3 on Monday November 19 2018, @11:10PM (3 children)

      by RS3 (6367) on Monday November 19 2018, @11:10PM (#764059)

      Almost every house has a microwave oven which is powered by, get ready for it: a vacuum tube, the magnetron https://en.wikipedia.org/wiki/Cavity_magnetron [wikipedia.org]

      I'm trying to envision the size and cost of a transistor-based RF amplifier that could do the same job (up to 1 KW RF output @ 2.45 GHz).

      Oh, and large radio / TV station transmitters are mostly powered by vacuum tubes.

      And still much very large power switching is done with ignitrons https://en.wikipedia.org/wiki/Ignitron [wikipedia.org]

      And large mercury-arc rectifiers are still in use.

      Let's not forget the traveling-wave tube https://en.wikipedia.org/wiki/Traveling-wave_tube [wikipedia.org]

      Nor the klystron: https://en.wikipedia.org/wiki/Klystron [wikipedia.org]

      Just for fun, the nuvistor https://en.wikipedia.org/wiki/Nuvistor [wikipedia.org]

      • (Score: 2) by VLM on Tuesday November 20 2018, @01:25PM (2 children)

        by VLM (445) Subscriber Badge on Tuesday November 20 2018, @01:25PM (#764231)

        I'm trying to envision the size and cost of a transistor-based RF amplifier that could do the same job (up to 1 KW RF output @ 2.45 GHz).

        That price has collapsed over recent decades.

        Your comments are true in a general sense thats slightly obsolete, but consider surplus markets. From memory the most recent "previous generation" of RF power amps to hit the surplus market that used vacuum tubes were those FAA control tower "dual use" amps that worked on AM civilian and military aviation freqs that sold REALLY well to ham ops about 30 years ago as surplus because the ham 2M band is between aviation civilian and military bands and they tuned down to 6M with little work (and worked pretty well on 220 MHz band too).

        Since then I don't recall any interesting surplus hitting the marketplace using vacuum tubes. The great NTSC analog to digital conversion and the infinite realignments since then dump some nice VHF-Lo and VHF-Hi linear power amps that hams liked converting to 6M thru 440Mhz bands but those have all been solid state AFAIK.

        There's still stuff around in use in the sense that there's news articles about companies using punch cards for inventory or whatever, but its basically so obsolete its even gone from surplus markets. They'll be stuff in museums. But vacuum tube gear hasn't hit the surplus market in significant mass since boomers were young. I remember my dad bought some vacuum tube VHF-Hi police radio surplus when I was a little kid to convert to ham radio 2M and that worked pretty well, but by the mid 80s that was hopelessly obsolete even for hams (no subaudible tones, poor performance, crystals, etc)

        Magnetrons are mechanical icky and someday those suckers are going to essentially be SMPS that happen to run at ISM microwave band freqs at 99% efficiency. The future is solid state microwave ovens that don't have cooling fans, anymore than my old fashioned heating element oven has a cooling fan. Probably another decade or two at most. Isn't the concept of a cooling fan in a heating appliance weird to begin with?

        • (Score: 1, Interesting) by Anonymous Coward on Thursday November 22 2018, @11:41AM

          by Anonymous Coward on Thursday November 22 2018, @11:41AM (#765153)

          > Isn't the concept of a cooling fan in a heating appliance weird to begin with?

          Sounds like you haven't used a new oven/stove/range with electronic controls? Smart man--the electronics doesn't add much except extra points of failure (and whizzy digital displays).

          The ones I've used have fans to cool the electronics--the fan comes on after the oven or heating element has been on long enough to get the control circuitry hot. And the fan stays on for awhile after the oven (etc) is turned off.

        • (Score: 2) by Virindi on Saturday December 15 2018, @12:31AM

          by Virindi (3484) on Saturday December 15 2018, @12:31AM (#774622)

          SMPS-powered microwaves already exist. Panasonic got a patent on the concept, they call it "Inverter Technology" (super original trademark, right? Except the output is rectified, so the name is a bit strange). There is one actual advantage: they can do faster pwm on the power to actually give you different power settings rather than just "pwming" a relay on the order of seconds. So of course they charge you more.

          And no surprise, it is much less reliable than the old type. We all know that is always the real goal, pack it with a lead-free SMPS which will short out and release magic smoke right after the warranty period is up.

          Recently I picked a recent 'inverter' model off the neighbor's trash; the waveguide tip of the magnetron was completely blown apart. It looked like someone had gone at it with an angle grinder. That is not a very common failure mode in traditional microwaves compared to failure of the control board...it makes me wonder if it was caused by SMPS failure.

          And by the way, the SMPS does still need a fan. The magnetron does as well. Even low voltage SMPS struggles to stay above 95% efficiency in real use, and we're talking about one with a several thousand volt secondary handling 1000w+. Even at 95% that would be 50w+ in the converter, plus the magnetron does heat up quite a bit on its own as well.

          If I were you I wouldn't be so keen to jump into the future when microwaves develop a tin whisker and blow up every 2 years. Like in every other consumer industry, I'm sure appliance manufacturers can't wait for this.