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Forward power and reflected power and transmitter and antenna matching

Discussion in 'Radio and Communications' started by sram, Aug 8, 2011.

  1. sram

    sram Member

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    Any sense in mounting them vertically like this?

    [​IMG]

    Uploaded with ImageShack.us


    These are two antennas, but you get the idea.

    ??
     
  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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  3. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    post#21.
    The problem with mounting two antennas like that: At the point of the camera you will get a gain of 2. Lets say the camer is north of the antenna. So N. and S. will get 2X. But East/West you will get near 0. (this assums the elementy are 1/2 wave appart) If the elements are some othere distance appart then the patern will be strange. I can predict if I know the distance.
     
  4. dave

    Dave New Member

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  5. sram

    sram Member

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    I did ask the guy I bought these from, but I doubt he will be more knowledgeable than you guys.
     
  6. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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  7. sram

    sram Member

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    Just a reminder, they are four antennas, NOT two. I only showed two because I'm not the best at drawing.
     
  8. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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  9. sram

    sram Member

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    Okay, I will. Thanks.
     
  10. sram

    sram Member

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    I didn't ask yet. But it does say here in this package:
    https://www.broadcastwarehouse.com/25kw-erp-transmitter-system/23/package

    that you need four antennas. And like the other website, it also says the polarization is vertical.

    So, when four are used....how are they mounted? I'll see if they will answer me.

    And this is the 4-way splitter I was talking about:
    https://www.broadcastwarehouse.com/label-/5kw--power-divider/731/product

    They also say 4 antennas are used to increase range without increasing power:

    >>ideal for feeding an array of antennas to allow you to increase your coverage area without having to upgrade your transmitter power.
    Standard models are 2-way, 4-way, 6-way, and 8-way dividers. Others available on request.>>
     
    Last edited: Aug 12, 2011
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It lists all the parts in that advert, and a single aerial is shown in this page:

    https://www.broadcastwarehouse.com/label-/aks/1n-800w-omni-dipole-antenna/906/product

    Presumably that's showing how it's mounted vertically?

    It doesn't say it 'needs' four aerials, I imagine it's specified with four in order to handle the much higher power transmitter.
     
  12. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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  13. sram

    sram Member

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    I did ask the question to more than one site, and I'm waiting.

    It boils down to this: The antenna polarization is vertical, but several antennas of the same type can be stacked for more gain. HOW should they be STACKED ?? That's the question. I'm sure you can figure it out ronsimpson.
     
  14. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    As far as I'm aware, you stack them vertically above each over, at the correct distance, and connected via a suitable phasing harness.

    I suspect you may do well to read this, particularly page 32:
     

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  15. sram

    sram Member

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    From my little search in google, it sounds like I should do something like this:
     

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  16. sram

    sram Member

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    Will do.
     
  17. JimB

    JimB Super Moderator Most Helpful Member

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    A very interesting document, thank you for posting it.

    However, there is a possibility that the guy who wrote it is an idiot and does not know what he is talking about!
    (There are many references to that unit which some of us believe should be abolished!:D:rolleyes:).

    JimB
     
    Last edited: Aug 12, 2011
  18. sram

    sram Member

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    Well, I think I found some mistakes in it. I'm in page 33 now.
     
  19. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Thank you Nigel, I see from post 11 we have what is on page 34 BUT you are driving the elements in phase not out of phase so the signal will be strong up/down and week N.S.E.W.

    I have used what is on page 32 many times. The elements are driven in phase. The length of the coax is the same for each antenna piece. Or they could be 1 wave length different. In my applications each element is delayed by 1 wave length. I ran the coax up the tower and "T" out every wave length. Some antennas are "T" out at 3/4 wave length.

    If you look at page 31, For a vertical antenna. The graphs on the left is seen from the top view. 0=north, 90=east, 180=s, 270=west. Page 34 shows power in all directions. If you look at your antenna it shows the south is 1/2 of north. South is the direction of your pole. So face the antenna toward the most people and the pole side the direction with the least people.

    Page 31 left side graphs. Top graph; 0=up, 180=down, 90 & 180 is to the horizon. This is for 1 element with a gain of 1.
    Page 31 left side graphs. Bottom graph; 0=up, 180=down, 90 & 180 is to the horizon. This is for 4 element with a gain of 4. The signal at 90 and 180 is 4x stronger. The signal at 120, through 180, is much much smaller and that is good. (4 elements 1,2,3,4 up/down the pole)
     
  20. sram

    sram Member

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    I was ganna say what do you guys understand from page 34. You caught it. But I'm not sure I understand what you want me to do now. Can you please re-phrase in simple english?
     
  21. sram

    sram Member

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    Sorry. double post.
     
    Last edited: Aug 12, 2011

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