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VHF booster

Discussion in 'General Electronics Discussion' started by Miguel Lopez, Aug 24, 2012.

  1. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    Hi all

    I need to build a TV booster for the VHF range (channels 2 to 12). I thought on a self-biased stage with a capacitor across the emitter resistor, using a Soviet 1T311 NPN transistor (Ge), because it is the only HF transistor that I have.

    My cuestion is about the configuration of the circuit. The self-bias configuration is stable and provide good amplification, but as I have never worked with HF, I don't know if there is a more suitable bias configuration.

    Any help welcomed

    Thanks

    Miguel
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Personally, I don't know why anyone would bother building one. They're very inexpensive to purchase (off the shelf) but if you insist on building it post the schematic.

    Edit: Oops, I just saw your location. You folks are still driving around in 1957 Chevy's that look like they just rolled off the showroom floor! Post the schematic.
     
    Last edited: Aug 24, 2012
  3. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    Oh, really!!?? I challenge you to find any in a Cuban shop.
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    You were too fast on the trigger. Go back and read my edit. BTW, Little Havana in Miami has lots of them. . :D
     
  5. CocaCola

    CocaCola

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    Apr 7, 2012
    Are import restrictions that bad, that it makes ordering and importing one from say China that complicated?
     
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    I wasn't kidding about the 57 Chevy. ;) Isn't Communism wonderful? :rolleyes:

    Chris
     
  7. CocaCola

    CocaCola

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    Apr 7, 2012
    Well I know there is a US trade embargo, but Cuba does do business with the rest of the world, including our neighbors to the North and South that enjoy cheap cane sugar that makes my drink of choice that much better vs the US stuff...

    I'm just hazarding a guess, but I suspect that sales between the Cuba and many other foreign countries would be nearly painless, as it's mainly a silly US policy only...
     
  8. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Most U.S. grown sugar is grown here in Florida and Hawaii. The price is high because of the EPA. No matter how you slice it, it isn't easy to get a lot of common things in Cuba and I don't think the US embargo has much to do with it. Hell, we don't make anything here anymore!
     
  9. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    Please, keep focussed.

    This is about a VHF booster, not about Cuba-US relationship. Open a thread in the Off-Topic Members Lounge section to talk about that

    I will post the schematic today.

    PS: Old cars (1940s - 1950s) in Cuba are as common as air.
     
  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Yes, you're absolutely correct. My apologies.

    Chris
     
  11. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    Transistor is 1T311 Germanium NPN (Soviet)
     

    Attached Files:

  12. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    A Germanium! Good grief! Actually, whether, Germanium, Silicon, BJT, FET or Vacuum Tube, that's not an RF amplifier by any definition.
     
  13. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    Ok, and what's the solution?

    Any suggestion?

    And, what's the problem with Germanium?
     
  14. CocaCola

    CocaCola

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    Apr 7, 2012
    My post were focused on the topic at hand, and were not off-topic... You simply ignored the on topic portions and twisted the remainder into something it wasn't...
     
    Last edited: Aug 27, 2012
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    For the rest of the planet they were superseded by silicon by 1970. I can't find a data sheet for your transistor and I'm not surprised. It's difficult to design around a transistor that you have no data for. Your transistor is a child of the Iron curtain era, which is not merely ancient history for me. I lived it. Fact: I can Google a 1930's vacuum tube data sheet and get hits. Soviet Germaniums?... Not so much.
     
  16. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    I'm agree with you that this is a dinosaur, but it is what I have. I've got some characteristic of this transistor that I can post here, basically maximun ratings.
    Would that be useful?
    And what about the circuit configuration?

    PS: This type was massively used on Soviet precision laboratory instruments such as frequency generators in early 90s. I retrieved them from one of these.
     
  17. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Post what data you have. Let's see what we can do with it. How many of them do you have?

    Curious,.. Are you trying to receive channel 7 in Miami?
     
  18. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    UCEmax = 12V
    UCBmax = 12V
    UEB = 2V
    Pmax = 150mW
    Ic = 50mA
    Hie = 30...180
    Fmax = 300 MHz


    Plenty

    Nop. I'm just trying to see channels 2, 4, 6 of national TV which are seen very poorly in my town. Channel 7 in Cuba is "Cubavisión" broadcasted from Pinar del Río.
     
  19. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    OK, I believe it should read like the following:

    Vceo Max: 12V
    Vcbo Max: 12V
    Vebo Max: 2V
    Pd Max: 150mW
    Ic Max: 50mA
    hFE: Min 30 Max 180
    fT: 300MHz ( Where gain = unity)

    Is this an NPN and do you know the noise figure?

    Chris
     
  20. Miguel Lopez

    Miguel Lopez

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    Jan 25, 2012
    Yes

    It is an NPN and I don't know the noise figure.
     
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