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4 - ELEMENT QUAD HELP NEEDED

Discussion in 'CB Antennas' started by unit_399, Sep 2, 2014.

  1. Shockwave

    Shockwave Sr. Member

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    As though this same novice couldn't be confused into using the grip dip meter to find resonance while completely overlooking the impedance match.

     

  2. nosepc

    nosepc On Vacation

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    [​IMG]
    At resonance, the input impedance of a decent-quality, correctly-mounted, HF mobile antenna in his best performance has will be about 25 ohms. By definition, the resonance point is where the reactive component equals zero (X=Ø, or +Øj if you prefer). Since the requisite impedance of our feed line is 50 ohms, the resulting SWR would be 2:1.
    A VNA can indicate the approximate resonance frequency of an antenna, a GDO gives the exact frequency.

    In the case of the cubical quad antenna, GDO use if you want it to work properly as it is a very narrow band antenna. The VNA indicates the impedance, and a frequency around.. But there is still people who believe that when an antenna is resonant impedance is 50 ohms, and that's a mistake, because each has a different antenna impedance, according to its design, fitness, nearby items etc. But beyond them ..

    A cubical quad antenna in his best performance has a 100 ohm impedance at the feed point, which means 2: 1 and SWR is correct !!
    However, the novice would reform the antenna up to show 1: 1, removing the antenna resonance, just to satisfy your S: W: R meter and VNA, and misconception of what is resonance, impedance, couplings, etc.

    Regards.
     
    #32 nosepc, Sep 9, 2014
    Last edited: Sep 9, 2014
  3. nosepc

    nosepc On Vacation

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    Hi, The DB, I explain. The GDO not require indication. The great frequency meters that exist today on precision indicate the frequency of cycles, so any resonant circuit is used, so it is wound on a finger.

    The antenna is coupled only when the resonance frequency thereof, and GDO is the same, and to an accuracy of frequency cycles, is read in the frequency counter.

    Nothing more is needed. It has not discovered anything new, the man reached the moon without VNA.

    Greetings.
     
  4. Shockwave

    Shockwave Sr. Member

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    How about you just put a 1/4 wavelength of 75 ohm coax on your 100 ohm quad and stop wasting peoples time here?
     
    #34 Shockwave, Sep 9, 2014
    Last edited: Sep 9, 2014
    wavrider likes this.
  5. nosepc

    nosepc On Vacation

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    Because the inclusion of quarter wave coaxial without first antenna tuned to resonance, charge could make 1: 1 SWR with 25 ohms, not 100 ohms probably not .
    Then it would be good to use a VNA or a vintage noise-bridge, "which probably does not work because they are very cheap".(The DB dixit)

    Many assume that the antenna works well, because the SWR meter reads 1: 1.
    A phantom load is also 1: 1 SWR, then it is a fantastic antenna?

    One thing not remove the other, but first things first.

    greeting. Ernesto.
     
    #35 nosepc, Sep 9, 2014
    Last edited: Sep 9, 2014
  6. The DB

    The DB Sr. Member

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    I don't know what language this is but it is not English... I guess you are trying to claim that your grid dip meter is a precision instrument again. Well, believe as you wish, its your mistake to make...


    I'm sorry to inform you, but no grid dip meter is accurate to cycles per second. There is also the fact that most are old, which brings up their chance of being out of specification... My VNA, however, is accurate to cycles per second as verified by me reading its output on my oscilloscope...


    Om my god, you are actually right about something, man has reached the moon before the VNA was invented. Man made it to the moon with computers that are far less powerful than this calculator sitting on my desk, does that mean that any modern computer that is faster than they used to calculate the data for the moon landing is also unnecessary?


    Why would he do this, that would make sense? After all, his leet grid dip meter has already found the resonant point he says he needs right?


    So you are saying that a resonant 100 ohm load will be converted to a resonant 25 ohm load by a 1/4 electrical wavelength 75 ohm feedline? You better redo your math because that is not right... The fact is it will be very close, actually just under, 50 ohms... Unless of course you are saying my smith chart is wrong, if you wish to say that you better have one hell of an explanation, because I know the smith chart to be correct, and I know why it is correct...


    The DB
     
  7. nosepc

    nosepc On Vacation

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    Yes The DB, you are correct, with 1/4 wavelength can also dock a load of 25 ohms, but not with 75 ohms, with 35 ohms but.
    Thank you, and Greetings.
     
    #37 nosepc, Sep 10, 2014
    Last edited: Sep 10, 2014
  8. Mudfoot

    Mudfoot Sr. Member

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    Meanwhile....

    JJ's building his quad.
     
  9. Jay in the Mojave

    Jay in the Mojave Active Member

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    Hello 399: The 10 Gauge wire will be just fine, as it will be insignificant as compared to 16 gauge wire for the tuning.

    I have made Quads and repaired Moonraker Antennas, and have noticed that the 14 gauge wire over time will stretch. I had some 10 Gauge enamel wire and used it as a quad wire. While marking the 4 points to be mounted on the fiberglass support arms, the 10 gauge wire was held in a Vice and pulled very hard to see what stretching would happen, and I could not measure any stretching, but the 14 gauge would slightly stretch when pulled on.

    What type matching are going to use?

    Good Luck. Jay in the Mojave
     

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