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What is this antenna called? Does it really work? What is wifi adaptor?

Discussion in 'General Electronics Chat' started by gary350, Aug 2, 2018.

  1. gary350

    gary350 Well-Known Member

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    • Funny Funny x 1
  2. dknguyen

    dknguyen Well-Known Member

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    I've seen those before on TV. I believe they're called death rays.
     

    Attached Files:

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  3. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Its a yagi disc.
    yes it probably does work if built correctly.
     
  4. dave miyares

    Dave New Member

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  5. ChrisP58

    ChrisP58 Well-Known Member

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    Well, I admit that I'm no RF or antenna engineer...

    The coax braid is soldered to the first disk.
    The coax center wire is soldered to the second disc.
    Those two discs are directly connected to the center bolt, and are therefore shorted to each other. (or did I miss an insulation step?)

    That just doesn't make sense to me.
     
  6. dknguyen

    dknguyen Well-Known Member

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    I dunno. Antennas are weird things to begin with
     
    Last edited: Aug 3, 2018
  7. carbonzit

    carbonzit Active Member

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    Yup. Remember that at radio frequencies, every piece of wire is actually an inductor ...
     
  8. dave miyares

    Dave New Member

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  9. BobW

    BobW Active Member

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    What video would that be?
     
  10. dknguyen

    dknguyen Well-Known Member

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    You can't see it?
     
  11. BobW

    BobW Active Member

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    Nope. Maybe I'm blind, but I don't see any link.

    Edit: I hit "quote" on the original post to see what was there, and saw that it was Facebook media. So my ad blocker probably intercepted it.
     
    Last edited: Aug 4, 2018
  12. dknguyen

    dknguyen Well-Known Member

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    It appears as a giant embedded video. You on a phone?
     
  13. BobW

    BobW Active Member

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    No. I'm on my Mac running Firefox.
    Anyway, don't worry about it. I rarely have the patience to watch giant videos.
     
  14. JimB

    JimB Super Moderator Most Helpful Member

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    RF is black magic.

    As a quick and dirty explanation:
    Something which is an odd multiple of a quarter wavelength long behaves like an open circuit.
    Something which is a multiple of a half wavelength long behaves like a short circuit.

    JimB
     
  15. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    As has already been said, it's a Yagi aerial, just with discs rather than rods - but I've no idea what effect that change will have? - a normal Yagi is polarised by the rods, so this 'presumably' will cover horizontal, vertical, or anywhere in between. However using slant (45 degree) polarisation on a Yagi means it receives both Horizontal and Vertical (FM radio is often broadcast as slant for that very reason) - BUT - you don't get something for nothing, and you make a 6dB loss in either case. I suspect the same will apply to this one.

    However, it will work fine (if built correctly) and greatly improve range - but obviously directionally.
     
  16. picbits

    picbits Well-Known Member

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    Do a search on Pringle Can antennas - they are quite fascinating too.
     
  17. carbonzit

    carbonzit Active Member

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    Saw this one years ago; what do y'all think of it?
    [​IMG]
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It looks like part of a short backfire array, but missing the reflector.

    The complete ones were relatively low gain, but good for anti-ghosting - we fitted many of them (the Wolsey Colour King) in areas where ghosting was a problem.

    Without the reflector it's going to be considerably lower gain, but bi-directional.
     
  19. unclejed613

    unclejed613 Well-Known Member

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    for a yagi, connecting the disks to the transmission line that way makes no sense. there should be one disk connected to the transmission line. this would be the driven element. all disks behind the D.E. are reflectors, and all in front are directors. yagi antennas can have all the elements except the D.E. connected directly to the metal axial support. the D.E. should be a ring, or a disk split down the middle with one side connected to the coax shield, and the other side connected to the center wire
     
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  20. gary350

    gary350 Well-Known Member

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    These are $12 free postage on ebay. My son has 1 he get wifi from McDonalds up the street. LOL That is the place it eats most often. Good customers get free wifi if they live close enough. LOL

    [​IMG]
     

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