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ASTROPLANE best vertical antenna ever?

Discussion in 'CB Antennas' started by nosepc, Oct 6, 2013.

  1. nosepc

    nosepc On Vacation

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    "The technique of studying a antenna by itself is to place is in free space, with no other object in its field in any direction whatsoever".

    This study is absolutely wrong.



    We are subjected to terrestrial magnetism, masts and antennas used, usually metal connected electrically to them, we must add the coaxial wiring it.

    Any study and gain of an antenna that does not include minimally these factors as well as the ground effect is almost absolutely useless and good for nothing.

    Physical modifications of the elements, if they influence the real world antennas

    a cordial greeting
     
    chip3655 likes this.

  2. The DB

    The DB Sr. Member

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    Am I reading this right? A top hat increases horizontal gain??? :confused:

    OK, lets look at what a top hat does logically. For one it adds reactance to the antenna, to compensate for this reactance we adjust the length of the antenna to maintain resonance. In the case of a top hat that means shortening the physical length of said antenna.

    That is fine, except physically shortening the antenna has the effect of making the horizontal lobes wider (by wider I am referring to more signal going further up and down rather than straight out), thus not as much energy is being directed out, this lowers maximum gain.

    Further, for those who worship "take off angles", being over an imperfect ground the take off angle of the antenna will go up. How far up depends on several factors, including the new physical length of the shortened antenna and the quality of the ground below it.

    Any positive effect the top hat *may* then have on take off angle or gain is overshadowed by the effects of physically shortening the antenna to compensate for the fact that it exists.

    Key word in the above section is may. *If* it makes enough of a difference that one could even measure, you are in the position of having to make up for what was lost before such a benefit *if it is actually a benefit* would come into play.

    The only way I can see such an antenna outperforming other antennas mentioned is if you mount it at the same tip height as the other antennas. For most people this form of comparison becomes less relevant as they will mount the antenna on the mast they already have or are putting up, whatever that height may be. After all, if they are adding another section of mast can they not also mount a longer antenna to that same point?

    But seriously, a top hat increasing gain??? Really??? I have never heard of a top hat being included on an antenna to either increase gain or lower a take off angle. With rare exception have I seen or heard of top hats being used for anything other than shortening purposes, and even then it is not the more common way of achieving that shorter antenna. I suppose there are the tiny top hats on some base antennas, but some manufacturers add them for reasons like "we think it makes the antenna look good"...


    The DB
     
    Needle Bender likes this.
  3. nosepc

    nosepc On Vacation

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  4. W5LZ

    W5LZ Crotchety Old Bastard

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    I'm afraid WB6BCN has some facts correct, but his conclusions are a little 'off'.
    - 'Doc
     
  5. The DB

    The DB Sr. Member

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    What was the point of bringing that article up? I fail to see how it supports your statements, at least the one(s) I'm referring to.

    The article does mention a top hat, but it is using it in combination with other loading (in the case of example 6 on the first page). It does not refer to a top hat on its own, and does not include any gain/loss figures or potential take off angle effects for top hats in the article at all.

    I'm confused as to why you linked to it here to begin with... :confused:


    The DB
     
  6. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Do you have a link showing that top hats do not increase efficiency?

    Serious, I would like to read that link.


    Or is it just your opinion?
     
    #51 wavrider, Oct 30, 2013
    Last edited: Oct 30, 2013
  7. The DB

    The DB Sr. Member

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    I didn't say a thing about efficiency so I'm wondering where you got the idea that I said or implied top hats are less efficient than they are. Perhaps you simply read that into what I said.

    As I was taking about gain, I'm assuming your referring to efficiency's effect on gain. If that is the case I will simply state that efficiency is not the only thing that effects gain.

    Edit---

    Oh wait, your referring to my post on the last page... I listed several aspects that will negatively affect the antenna simply because it was shortened. Are you going to tell me that any added efficiency from a top hat will overcome the effective losses in gain that shortening the antenna will have?


    The DB
     
  8. bob85

    bob85 Supporting Member

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    the astroplane was designed specifically to make the most of the then current height regulations for cb antennas, the patent explains it,
    the hat raises the current maxima vs other antennas at the same tip height but not by the margin avanti claim,

    they tell us prior art antennas radiate most from the bottom and give us drawings from the advertising department showing the astroplane suffering from less shadowing, that's technobull,

    conventional antennas like clr2's magnums wilson 5/8 and other contemporary antennas all radiate most 1/4wave down from the tip, the astrpane has at best 1/8w height advantage of current maxima,

    avanti tell us the hat on the astroplane reduces efficiency and gains a wider bandwidth when compared to a straight 1/4wave,

    removing the hat loses you any advantage the astrplane may have due to the raised current maxima when mounted at the same tip height as other antennas,

    hats contribute very little to far field radiation.


    Where Do I Hang My Hat?
     
    1 person likes this.
  9. bob85

    bob85 Supporting Member

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    the article nosepc posted the ink to is dealing with shortened 1/4waves like a coil loaded 8ft antenna on hf where the physical height of the antenna is a small fraction of a wavelength and radiation resistance is very low.
     
  10. nosepc

    nosepc On Vacation

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    Avanti says the ASTROPLANE has 4.6dBi, something 1dBi over the best 5/8.

    To me it is a coaxial antenna induced capacitances for a good decoupling of the feed line, and that this does not interfere with the lobes of irradiation.

    It is true that the top hat also serves to respect regulations then.

    But it also serves to balance the capacitances of the skirt.

    at least, so I see it.



    Historical photography, ASTROPLANE interesting times

    Herb Blaese (WB9PXD) holding a black top hat and Lou Martino (W9DSG) points out .

    Next you see a instrument that looks RF generator, analyzer and surely perhaps field analyzer.

    [​IMG]
     
    #55 nosepc, Oct 30, 2013
    Last edited: Oct 30, 2013
  11. bob85

    bob85 Supporting Member

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    in the artice that goes with that magazine cover the avanti engineers said they did not understand exactly how the astroplane works,
    im possiby avanti's biggest fan, mainy because their antennas are different and controversial, and they used the best quaity aluminium used in any cb antenna i have owned,

    where did you get the idea the astroplane has about 1Db more gain than a 5/8wave,
    avanti claim 5.14Dbi for their 5/8 sigma2 and 6.14Dbi for the sigma4.

    [​IMG]
     
    #56 bob85, Oct 30, 2013
    Last edited: Oct 30, 2013
  12. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    You referenced Example 6 that is SIX which states TOP HAT loading is the most efficient.

    SO your statement is true. YOU did not say anything about efficiency.

    NOW where is that link stating that TOP HAT LOADING is not the most efficient form of loading an antenna.??????????
     
  13. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    DB I agree 100%. Shortening an antenna will decrease, gain, efficiency etc,etc.

    How much will it be decreased? Not a lot. Maybe not so much as to be noticed by the receiving station
     
  14. HomerBB

    HomerBB Sr. Member

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    I am enjoying the dialogue.
    You fellows keep working on this bone. We all can benefit from a bit of debate that digs up knowledge.
    However, I will remain the empiricist I am, and when it is all said and done, putting one of these controversial antennas to the work on a well mounted perch answers all the necessary questions for me -
    1. Does it work? Yes
    2. Does it work well? Yes
    3. Does it work as well as any other 1/2ƛ or 5/8ƛ I've used? Yes
    4. Does it work better than some of these I've used? Yes
    5. Is there a necessary way to mount it to obtain maximum performance? Yes
    6. How do I get the most from this antenna? Up high and clear.

    For it's size, weight, and elegance of style, it rocks.

    That is why I plan on building another - simply as a tribute to it's perfection.

    (edit) I should add. I want to know all the science behind antenna theory. i want to see how it plays out in the real world, too. Loving this thread.
     
    #59 HomerBB, Oct 30, 2013
    Last edited: Oct 30, 2013
  15. The DB

    The DB Sr. Member

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    Removed by The DB
     

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