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Difference in AstroPlane vs. New Top One per Eznec5

Discussion in 'CB Antennas' started by Marconi, Apr 26, 2012.

  1. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    For consideration, here are my two Eznec models at 48' feet to the mounts for the old Astroplane/Top One, and Sirio's New Top One (NTO). My modeling efforts for each antenna was to try and get them as close to specs as possible.

    I've added the first page as an overlay of the radiation patterns to allow for easy comparisons. The pattern in black (* Primary) is the New Top One and in blue is the AstroPlane.

    I think these two are similar antennas, because according to Eznec their performance is almost identical and where differences are noted they are likely due to some height differences that I did not adjust to make equal for this project. The heights were close enough, but see note below.

    I also find that these two seem to work the same in my real world testing, either side by side, and while standing alone using the same antenna system.

    I think these two are basically center fed 1/2 wave antennas, not a 5/8 wave or 1/4 wave. They also perform similar to an end fed 1/2 wave model...which I've also included in this project for consideration. They look like center fed 1/2 wave too.

    Personally, I consider the traditional 1/4 wave ground plane with horizontal or slanted radials a 1/2 wave antenna too.



    Notes: all antennas were set at 48' feet for the mast as noted above, so due to construction differences they are all at a little different height, and that can make a subtle difference in the results you see here.

    I also do not consider either antenna to be tunable as per instructions, specifications, or construction when set as instructed.

    To support this idea regarding tuning, I've attached a bandwidth curve for my Sirio NTO with the gamma match feeder as well. Note that the SWR and VA1 analyzer bandwidth curves both indicate a nice flat working SWR range under 1.3:1, from 26.5 to 28.5. This is the same as noted in Sirio's specifications for the NTO's frequency range, so no tuning is necessary or needed.

    View attachment AstroPlane vs. New Top One.pdf
     

  2. HomerBB

    HomerBB Sr. Member

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    If I read it right it appears the NTO had a 0.09dbi over the AP in the lowest lobe, however, It seemed the secondary major lobes were superior in the AP to those of the NTO in terms of lower DX angles.
    Did I see that correctly?
     
  3. gamegetter

    gamegetter Well-Known Member

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    very interesting

    With differences showing up after the primary lobe which may possibly be attributed to the height difference of the antennas but pattern is the same.

    I still studying the graphs on wavelength and trying to figure out why Sirio called the astroplane a 5/8.

    Thanks for the topic opener, good day.
     
  4. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    gamegetter, I agree. I also consider the patterns pretty similar, but Sirio notes in their manual that the New Top One is a 1/4 wave antenna.

    However, I haven't seen anywhere that Sirio called the astroplane a 5/8 wave. Some years ago I argued the same point, that the AstroPlane was effectively a 5/8 wave radiator.

    Homer, like gamegetter suggested above, the little difference you see in my results might be due to the height differences.
     
  5. gamegetter

    gamegetter Well-Known Member

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    old astro plane box-pic

    i gathered from a pic of an original box that the antenna was at least "called" a 5/8. I'm sure you have the patent #, it is also on the box.

    forgot to attach pic!
     

    Attached Files:

  6. gamegetter

    gamegetter Well-Known Member

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    close up pic

    attached
     

    Attached Files:

  7. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I can't read the print on the box, does it show 5/8 after the word Patented near the bottom?
     
  8. gamegetter

    gamegetter Well-Known Member

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    i added a close up, we posted at about the same time.
     
  9. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Thanks, I stand corrected. Personally, I consider that display to be like eye candy, to lure the buyer, but its there for sure. I've read the patent a few times, but I don't recall it appearing there, but I could have missed it.

    Like I said earlier, Sirio refers to the NTO as a 1/4 wave ground plane in their manual, so that is good enough for me.

    To tell the truth though, a 1/4 wave ground plane with horizontal radials at 48' feet does look to make a pattern very similar to my pattern for the NTO @ 48'. So, even though I tried, I guess I can't really support my point the the A/P, and the NTO, are 1/2 waves.

    View attachment .25 w with horizontal radials at 48'.pdf
     
  10. gamegetter

    gamegetter Well-Known Member

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    but they are definitely the same critters, what critter is the subject of the thread no doubt...i have always been interested in just what exactly the astroplane was.

    thanks for your graphs and insight.
     
  11. gamegetter

    gamegetter Well-Known Member

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    I am leaning towards the 1/4 wave or perhaps an 1/8 wave?

    think about it back when the astro plane was designed they took into account the height restriction of cb antenna, which was 20'. You take a 20' foot mounted 1/8 wave and
    you have a 5/8 wave.

    so i really think it is much closer to 1/4 or an 1/8 wave
    the difference if it is one or the other was the "electrical" difference.
     
  12. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Gamegetter, read the AstroPlane Patent Abstract closely. Consider what is physically and electrically described, and then tell me what wavelength it describes. The file goes on to describe a 1/8 wave top element which is capacitively load with a 1/8 wave top hat and terminates at the first level. There are two 1/4 wave elements that extend downward from the first level to a 2nd level. What does that describe?

    AstroPlane Abstract (495x640).jpg
     
    #12 Marconi, Apr 26, 2012
    Last edited: Apr 26, 2012
  13. gamegetter

    gamegetter Well-Known Member

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    wow, this will open some discussion, thanks for posting that...i want to read it some more this evening and let it soak in.
     
  14. HomerBB

    HomerBB Sr. Member

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    1/4 down, 1/4 up
    kinda simple, no?
     
  15. doesn't the astroplane need a certain minimum length of mast to tune/work properly ? If i recall correctly and it does , shouldn't that be included in the overall length that makes it usable ? i may be remembering wrong though , so someone correct me if i am please .
     

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