1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

ASTROPLANE best vertical antenna ever?

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

  1. bob85

    bob85
    Expand Collapse
    Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,789
    Likes Received:
    585
    if you mean the sirio top-one i would view that as a hat loaded dipole with a fat ass, or a hat loaded 1/4wave ground-plane that acts like a dipole,

    it would be interesting to measure an astro without the mast to see what the loop impedance is, if its not pretty high without the mast then i need a rethink on how it may work.


     

  2. Shockwave

    Shockwave
    Expand Collapse
    Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    2,540
    Likes Received:
    760
    As I'm sure you know, the mast is an important part of the Astroplane. Do you see the Astroplane and the Top One as being significantly different in how they work? Unless I'm overlooking something, I see them as very similar with the difference being the feedpoint.

    They have moved the feed to a lower impedance part of the element where the gamma match could be used to tune the antenna. I imagine if the location were moved far enough this could cause a change in how the currents were distributed along the element.

    Do you think this may cause the two antennas to perform differently? I haven't investigated any of this so at the moment I have no opinion and am curious what your thoughts are?
     
  3. Z-MAN 369

    Z-MAN 369
    Expand Collapse
    Active Member

    Joined:
    Dec 21, 2012
    Messages:
    148
    Likes Received:
    22
    My answer to the question is.......no. Im very well acquainted with this/these Astro's, an A99 can outperform one easy, lol. Here is a 20yr old pic i found of my buddys (i used to take pix of all my friends antennas with a Fuji disposable cardboard camera) This is still standing today.
     

    Attached Files:

  4. bob85

    bob85
    Expand Collapse
    Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,789
    Likes Received:
    585
    simliar as in both been hat loaded 1/2waves with similar performance yes, but don't see them as the same type of antenna,

    the only transmission-line mode currents i see in my minds eye with the top-one are circulating within the gamma section opposite in direction to antenna mode currents,

    with the astroplane the feedpont impedance is set by the spacing of the legs to the mast forming the transmission-line,

    i could be wrong but that sounds to me like a 1/2wave monopole with a 1/4wave sleeve mounted on a 1/4wave mast turned upside down,

    a cst plot would show us what we need to see,
    it either has radiation on the outside of the legs flowing the opposite direction to transmission-line mode currents inside the legs or it does not and i need a rethink on how it may operate.
     
  5. HomerBB

    HomerBB
    Expand Collapse
    Sr. Member

    Joined:
    Jan 4, 2009
    Messages:
    2,868
    Likes Received:
    630
    My personal experience with the AP and the A99, and my own homebrewed EFHW antennas without radials has been conclusive to my opinion that the A99 would have to wake up in heaven with angel's wings to work as well as the AP.
    when I have brewed and tuned meticulously an EFHW with radials it has out performed all other EFHW antennas I've used.

    As for checking the impedance of an AP without the mast, I will try it when I build another one. However, I suspect the RF current will simply utilize the coax instead. Maybe I can figure out how to directly connect the 259b to the antenna and still read it.
     
    #20 HomerBB, Oct 10, 2013
    Last edited: Oct 10, 2013
    Needle Bender and hotrod like this.
  6. bob85

    bob85
    Expand Collapse
    Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,789
    Likes Received:
    585
    homer, you could try bringing the coax away at right angles to the top bracket or hook the 259 right to the connector, im sure you can figure out how to get the structure in the clear without the mast,

    if you drop the coax down between the legs it will use the coax outer braid as avanti tell us.
     
  7. nosepc

    nosepc
    Expand Collapse
    On Vacation

    Joined:
    Apr 12, 2013
    Messages:
    187
    Likes Received:
    8
    ASTROPLANE .NEC

    :bdh:


    I am convinced that the antenna support astroplane greatly influences the performance of the same.Surely the bulk of the mast diameter produces losses in the antenna.You need to make the antenna astroplane the same diameter or thicker to radiate efficiently

    :bdh:

    [​IMG]

    :bdh:
     
    #22 nosepc, Oct 10, 2013
    Last edited: Oct 11, 2013
  8. HomerBB

    HomerBB
    Expand Collapse
    Sr. Member

    Joined:
    Jan 4, 2009
    Messages:
    2,868
    Likes Received:
    630
    Yeah. My thoughts exactly.
     
  9. Marconi

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

    Joined:
    Oct 23, 2005
    Messages:
    5,511
    Likes Received:
    593
    Bob, in order to try and clear up the issue for me, where you reference the term transmission line (TML) currents often in your posts. Do you see these type currents flowing in a typical top hat, setup in the crossed (+) configuration that are horizontal to the radiator or does you mind's eye tell you the currents in a top hat are always antenna mode currents?

    Also, is what you see happen with horizontal radials attached to a vertical radiator...also producing transmission line currents, or again do you typically see antenna mode currents in radials that radiate well into the far field?

    Do these two terms TML/AMC have anything at all to do with cancellation or the results of cancellation?

    Are antenna mode currents (AMC) the opposite of TML currents...in that they do radiate into the far field while the TML currents do not for the most part?

    I've always heard and understood that radials and top hats can effectively provide a path for return currents that allows for improved symmetry and decoupling of the coax at the feed point of a resonant radiator.

    It is also my thinking...that these same currents do not radiate effectively into the far field as a result of the feed point being well balanced, and this is due to cancellation of parallel currents that are out of phase in such case, where we have currents flowing in the opposite direction...even if the magnitudes are the equal or not.

    Does the instance of cancellation have any at all to do with transmission line currents and theory?

    I've also heard that the currents that flow in the loop created by a typical gamma install works without effective radiation into the far fiedl due to cancellation, and I see these circular loops we find on the S4/Vector and the Astroplane also
    do the same, where I see 1/2 the loop being out of phase with the other 1/2.

    I hope this make sense?
     
    #24 Marconi, Oct 12, 2013
    Last edited: Oct 12, 2013
  10. bob85

    bob85
    Expand Collapse
    Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,789
    Likes Received:
    585
    i would not say you have significant transmission-line mode currents in the top hat or horizontal radials eddie, i don't think either add to the far field radiation,

    as you sweep the radials up towards the monopole the transmission-line mode impedance that is seen in parallel with the monopoles antenna mode impedance comes down causing tm current to increases,

    what radiates under what conditions is explained in the arrl open sleeve article,


    this may shed some light on it The Coaxial Folded Monopole
     
  11. nosepc

    nosepc
    Expand Collapse
    On Vacation

    Joined:
    Apr 12, 2013
    Messages:
    187
    Likes Received:
    8
    If you start playing with a groundplane antenna to optimize the maximum with 4NEC2 ...



    The result is one TOP ONE .... ;)
     
  12. Shockwave

    Shockwave
    Expand Collapse
    Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    2,540
    Likes Received:
    760
    Both the GM and Vector will easily exceed the range of a Top One.
     
  13. nosepc

    nosepc
    Expand Collapse
    On Vacation

    Joined:
    Apr 12, 2013
    Messages:
    187
    Likes Received:
    8

    I took the trouble to make an antenna 5/8 wave like "A VERTICAL ANTENNA BEST CB "with the program 4nec2, 12 meters high, with its own MAST, (absent in all the "patterns" of sellers)

    Shows that these antennas have a 18dbi NEGATIVE lobe between 5 and 15 degrees above the horizon,

    Makes these antennas? worst for CB'ers??



    [​IMG]


    herein can see that the best angles for DX are between 1 and 13 degrees ON THE HORIZON.

    http://radio.n0gw.net/radio12.pdf

    :unsure:
     
    Needle Bender likes this.
  14. W5LZ

    W5LZ
    Expand Collapse
    Crotchety Old Bastard

    Joined:
    Apr 8, 2005
    Messages:
    6,832
    Likes Received:
    749
    There is no 'best angle' for DX, that's just silly. Those signals can arrive at almost any angle not just the lower ones. Sure, it's nice to have those lower angle reception abilities but it's certainly not an absolute requirement at all. All this DX angle stuff is supposition, not fact at all. What about all the antennas that don't have those lower angles of propagation and work DX anyway?
    - 'Doc
     
    1 person likes this.
  15. nosepc

    nosepc
    Expand Collapse
    On Vacation

    Joined:
    Apr 12, 2013
    Messages:
    187
    Likes Received:
    8
    Because using powers above 12 watts?? :unsure:
     

Share This Page