Do RF amps still use tubes?

Discussion in 'General Electronics Chat' started by Paulo540, Jan 2, 2010.

  1. Paulo540

    Thread Starter Member

    Nov 23, 2009
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    Hi,

    currently studying RF amplification and they are covering a lot of tube applications. Just curious if these are still used in modern or still running applications. And if so, what, in your opinion would be the benifit?
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Not really.
    There are nowerdays also RF amplifiers that us mosfets and other transistors.
    It also depends on the power needed at wich frequency.

    Here is an example of a 1kW peak Hamradio amplifier, with mosfets:
    http://www.reimesch.de/expert.html

    Greetings,
    Bertus
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    I have read that broadcasting stations still use tubes in the final stage. I do not know if it is true longer. My knowledge may be outdated.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello t06afte,

    You are right for broadcast stations.
    They mostly need more power.

    We use only transistor transmitters in our NMR systems.
    The powers can be upto 2.5kW.
    They will produce small pulses of that power with a delay in between.

    Greetings,
    Bertus
     
  5. VoodooMojo

    Active Member

    Nov 28, 2009
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    High power radio transmission is the main user of RF tubes. Many are still in use and no plans in the near future to make them extinct.

    Many applications have been changed to Power Transistors with superb results as Bertus points out.

    Interesting enough is check e-bay and watch what people are bidding like crazy on....tube testers! go figure.
    like thats the only way to check tubes.

    being you are studying them you will be researching the pros and cons of both, but to answer your immediate question, yes, they are here, and after the big nuclear bang, they, along with the cockroach, will still be here.

    the tube thing is not going away.
    I make a gift for a friend. A Nixie Clock, now I have dozens of requests!
    as I said, go figure.
     
    Last edited: Jan 2, 2010
  6. ELECTRONERD

    Senior Member

    May 26, 2009
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    Microwaves still use tubes in the magnetron and the military still uses tubes. To get the kind of power for a microwave (hundreds of watts), only a tube can provide that power with a less exorbitant price, and so on. However, GaA and GaN devices are now being used and their performance is increasing gradually; they are mostly being used in the military at the moment.

    Austin
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    For really high power levels tubes are still king, but they don't handle really high frequencies well. I suspect they will be used for commercial radio stations for a long while.
     
  8. Paulo540

    Thread Starter Member

    Nov 23, 2009
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    Thank you all for commenting, it makes me feel better that my coursework is still very relevant. Plus, I think tubes are cool (figuratively) and look forward to working with them.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Something my school did was set up a field trip to a local AM/FM station. The station engineer opened up the cabinet and showed us his tubes. These suckers were giants, measuring about 1½' tall and around 1' in diameter, and there were two of them.

    You might see if your school has ever done anything similar. You might be able to set something similar up, most engineers are proud of their equipment.

    When I first hired onto Rockwell/Collins Division they hadn't sold off their commercial broadcast division, it was in the building, so I got to see some of the equipment built back when Collins Radio was still a name.
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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    Perhaps the "overunity" people should look into tubes. As I understand they need about 13 Mhz and a lot of power, to do their magic with water. I guess it would not work better, but certainly look more impressive
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Only thing special about 13.57Mhz is the FCC lets you play with high power. It is used for a lot of things.
     
  12. t06afre

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    So that is the reason. I have never looked into overunity because I actually do have a degree in physics.
     
    Last edited: Jan 4, 2010
  13. Paulo540

    Thread Starter Member

    Nov 23, 2009
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    LOL.

    Well, obviously, you can just take the heat from the tubes and run a steam boiler and then power a generator that supplies the plate voltage and then you can take the parasitics off with a quarterwave-googoogaga-asymetric-quasispherical-moduflaxseed-coupler-antenna (patent pending) and recombinate them into energy to power thousands of homes.

    Problem solved.

    tapping feet with arms crossed pending notification of nobel peace prize nomination
     
  14. t06afre

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    I will fit my HHO modified Delorean with tubes asap. I think this will be the first time in modern science/history this has been done ever:cool:
     
  15. Paulo540

    Thread Starter Member

    Nov 23, 2009
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    Do what you wish, just make sure you tune the flux capacitor tank circuit to 1212.2012 gerflapahertz so that you simultaneously disrupt the impending mayan armaggeadon whilst you embark on your free-energy time-travels/media junket.

    two-birds/one stone.
     
  16. lmartinez

    Active Member

    Mar 8, 2009
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    Do you enjoy music? A vaccum tube has the appropriate electrical parameters for a good audio amplifier and for an RF electrical circuit you might as well buy acres of land to build an equivalent electrical circuit......
     
  17. t06afre

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    May 11, 2009
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    Even if the OP asked for RF applications, so it is true that many like the sound from a tube amplifier. As I have understand a tube amplifier will produce a much "warmer" sound than semiconductor amplifier. I do not how much truth it is in this statement ;)
     
  18. beenthere

    Retired Moderator

    Apr 20, 2004
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    I often wonder is anyone can really distinguish between tubes and transistors with the same musical selection played through the same speakers. Or if the wires are oxygen free, or the connectors gold plated.
     
  19. t06afre

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    Some of my friends are HIFI nuts. Then they invite me home to brag about the their newest purchasing I just let them do most of the talking (usually not a problem), and just insert enough "I see", "very interesting", "fantastic", "cool" and so on. They are my friends and I do not want to disappoint them:rolleyes:
     
  20. Audioguru

    New Member

    Dec 20, 2007
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    Some hi-fi amplifiers have a solid state circuit but have some tubes glowing on top. The tubes are only to see since they do nothing but make light and heat. They sound exactly the same as a solid state amplifier.

    Many tube amplifiers have a fairly high output impedance that does not damp the resonances of modern speakers that are designed to be damped by the extremely low output impedance of a solid state amplifier.

    Many tube amplifiers have even-harmonics distortion that sounds musical to some people. They clip "gracefully" which makes them sound louder than they actually are.
    They have the high audio frequencies rolled off by the output transformer which makes a "warm" (muffled) sound that some people like.
     
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