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Transistor Amplifier Tuning

Discussion in 'Amplifiers' started by Shadetree Mechanic, Apr 2, 2021.

  1. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I found this video about input and output tuning using a Nano VNA. I need to get one now, please join me on a trip into the rabbit hole. Any and all comments welcome.



     

  2. groundwire

    groundwire Sr. Member

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    You can also use an antenna analyzer like the rigexpert as well
     
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  3. Shockwave

    Shockwave Sr. Member

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    How come he doesn't sound like BBI?
     
  4. nomadradio

    nomadradio Analog Retentive

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    Only works with linear amplifiers. The tiny drive signal you get from a VNA won't even be noticed by a class-C "competition" amplifier. Needs more drive than that to turn on the transistors. I've been wishing for a 100-Watt VNA for decades.

    73
     
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  5. Trailblazer

    Trailblazer Supporting Member

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  6. caliusoptimus

    caliusoptimus Member

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    Check out the LP100A. It's an inline watt meter that also reads complex impedance. I'm sure it's not as precise as a VNA but... the price tho.
     
  7. nomadradio

    nomadradio Analog Retentive

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    It won't resolve the sign of X, the reactive component. But it will show you the magnitude of X.

    The sign is easy to determine. Just change frequency. If the value increases with a higher frequency it's inductive. If it drops when the frequency goes up, it's capacitive.

    Yes, Larry's LP100 should tell you what you want to know, while running a realistic drive level. The actual input impedance of most amplifiers will change in step with the drive level. Takes a wattmeter or SWR meter to see that.

    73
     
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  8. Shockwave

    Shockwave Sr. Member

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    Much more so with a class C amplifier too and on SSB, the input impedance is all over the board in between words and peaks.
     
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