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MACO VQ3

Discussion in 'Amateur Radio Antennas' started by Mudfoot, May 3, 2019.

  1. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    Thought the whole delta loop thing was preferable to yagi. Isn't this just a triple delta loop? Why should those data sheets be a fantasy? They match or beat typical 11m yagi 4 element gain figures, or are you saying all of the 11m gain figures are fantasy, from all the beam manufacturers, type irrelevant. I'm not sure I quite follow. Not attempting to be tricky I'm just not sure I'm following correctly.


     

  2. Justme

    Justme Sr. Member

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    First of all no comparison given dB gain to what? dipole? dummy load? Isotropic raadiator?
    Simply gain of an beam is depending on length of the boom, number of elements.
    My 2.5 wavelength 2 meter beam from Flexa yagi , 12 elements and excellent design had 12.4 dBd gain.
    I have seen omniderectional antenna's for CB seen advertised with over 10 dB gain.....
    Most 3 element beams have an gain of 5.5 dBd gain ( over dipole).
    Chosing an larger boom length also makes the back less tight, but gain can be max 8.4 dBi never 14.5 ...
    Front to back ratio will be lower as well on long boom beams.
    Swr for a long boom beam is also narrower as a short boom beam.
    Have a read up:
    3-Element Yagi (antentop.org)
     
    Shadetree Mechanic likes this.
  3. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    I was given to understand "dBi" WAS a measurement as compared to an isotropic radiator. Is that incorrect? I absolutely have no experience with beams.
     
    #18 lonestarbandit, Jun 20, 2021
    Last edited: Jun 21, 2021
  4. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    DBI is rated over Isotropic...The Isotropic antenna technically only exists in a vacuum.
    There are several antenna GURU's that will state the Horizontal Dipole over good Earth has the possible gain of 8 dbi.
    I am with Just Me that antenna has a gain of maybe 6 DBd (6db over a dipole)
    Did you also notice that Monster weighs 36 lbs...No TV rotor hold that up for long!
    That should require a HAM III or HAM IV rotor.

    I'll take a 4 element yagi...Horizontal at 30 to 40ft... ANYDAY over that antenna.
    IMHO:)
     
    Justme likes this.
  5. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    Well THAT one does. The maco is 28 pounds.
    Also well shit. I already ordered it (maco vq3 that is) and havent room for 4 element yagi.
    So I should expect a 6 db gain over a dipole aka omni aka what I have a Imax2000 or less than that even? Although I assume 6 db directed gain would be at least noticeable over the omni? I'm just hoping now cause this things 340ish delivered.
     
    #20 lonestarbandit, Jun 21, 2021
    Last edited: Jun 21, 2021
  6. freecell

    freecell Active Member

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    BJ radionut posted:

    "The Isotropic antenna technically only exists in a vacuum."

    the isotropic radiator radiator doesn't exist, it's based on a theoretical construct.

    isotropic (source) radiator

    the point of origin for the purely omnidirectional radiation of electromagnetic energy located at the absolute center of a sphere which radiates energy of equal intensity at all points of the inner surface (effective area) of the sphere. the isotropic radiator exists only in theory since construction is impossible but it is useful as a reference by which to gauge the directivity of electromagnetic radiators.

    the directivity of the isotropic radiator is 0 dB. and the power multiplier ratio is 1.

    from this reference point it is clear that any effort to concentrate or focus the energy produced by the radiator (for example, the addition of a parabolic reflector) in an effort to increase the intensity of the radiation to any fractional area of the internal surface of the sphere will distract from the intensity of the radiation in the direction of large portions of the sphere's internal surface and will produce an increase in directivity in the favored direction relative to the placement of the reflector element with respect to the radiator.

    https://www.worldwidedx.com/threads/best-low-cost-intro-beam.261866/page-3#post-764374
     
  7. freecell

    freecell Active Member

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    lonestarbandit posted:

    "or are you saying all of the 11m gain figures are fantasy, from all the beam manufacturers, type irrelevant."

    all gain figures for all antennas are irrelevant in the absence of a determination of the radiation efficiency of the antenna in question. until then we can only speak in terms of directivity.

    dB. gain = 10 log (power out / power in)
    dB. loss = 10 log (power in / power out)

    unfortunately, gain cannot even be calculated until the radiation efficiency of the antenna has been determined. until then, directivity is all that can be discussed. the
    same could be said in regard to system losses.

    gain = radiation efficiency X directivity.

    gain and directivity are differentiated. you can have an antenna with 3 dB. of "directivity" (at some angle) but if the radiation efficiency of that antenna is only 50% then "gain" is only 1.5 dB.. directivity does not automatically equal "gain" unless all antennas are assumed to be 100% efficient. i promise you that is not even the case, particularly where commercially manufactured antennas are involved.

    https://www.worldwidedx.com/threads/ground-mounted-verticals.261639/#post-
    764104
     
  8. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    Well thats true... Basic physics really.
    But what real world performance gain over my Imax2000 should be expected?
    Hoping its not a total waste of money now.
     
  9. Crawdad

    Crawdad Down in the mud invasive species

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    www.w8ji.com/end-fed.htm has one very well respected ham's opinion on what to expect from end-fed vertical antennas.

    73
     
  10. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    it isnt there. 404 error.
     
  11. freecell

    freecell Active Member

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    lonestarbandit posted:

    "But what real world performance gain over my Imax2000 should be expected?"

    if no one knows the radiation efficiency of either antenna then the gain for either antenna cannot be determined. generally speaking, almost any directional antenna is going to be able to outperform an omnidirectional antenna over some range of radiation angles based on the fact that it's "directional."

    the sigma IV was advertised as having a maximum directivity of 6.14 dB. and no "i", leaving many to believe that since the "i" did not appear that the dipole must have been the reference antenna, which would be equal to 8.29 dBi but we read in the avanti patent that it was found to produce a maximum directivity of 2.2 dB. over a dipole, 4.35 dBi.. this is hilarious since the directivity for the astroplane was given to be 4.46 dBi.. any reasonable individual at this point would be led to believe that the astroplane outperforms the sigma IV.. think about it.

    they're in business for two things, to feed you and sell you on their b.s. and move large amounts of overpriced aluminum.
     
    #26 freecell, Jun 21, 2021
    Last edited: Jun 21, 2021
  12. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    That is absolutely true. And it worked I ordered the over priced aluminum.
    Hopefully its not absolute rubbish
     
  13. Crawdad

    Crawdad Down in the mud invasive species

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    My bad. You can get to it from www.w8ji.com then. Just takes a few extra clicks. Worth the read if you use one of the fiberglass pasta antennas.

    73
     
    lonestarbandit likes this.
  14. lonestarbandit

    lonestarbandit 4-2-9 Central TX

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    Yeah I do have a imax2000 presently ill have a look.
     
  15. Justme

    Justme Sr. Member

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    It is all relative.
    I use the Imax 2 K here not because it is the best antenna for CB or 10 meters, but because it works well on 10/11/12/15/and with tuner on 18.
    On 10 i still worked all continents with it as i did on 12 and 15 and 18.
    Would a dedicated narrow band higher gain vertical work better? yes, but i don't have the space for all these antenna's so the Imax 2 K has to do, and still gets around the world.
    It is conditions that will make that possible, not the 1 or 2 dB difference in antenna.
    I feed the Imax with LMR 400 type cable all 60 feet of it.
    On 15 and 18 it is still an endfed 1/2 wave hence it works there as well.
    Been doing that for over 20 years now, and having worked the world around on these bands that antenna is good enough for me here in my situation.
    If you only work on CB get another antenna up, narrow band higher gain and better for what you want to do.
    There are no mirracle antenna's out there.
    Just good ones and fantasy ones....for Cb that is, you won't see overstated claims for Ham antenna's, we mostly understand too well these claims are bogus.
    Gain has to come from somewhere, your antenna gets 100 watts it does not magically amplifies that to 400 watts, it just directs part of that 100 watt in an certain direction, attenuating power in other directions.
    For a beam it is attenuating every power to the back, have a narrow beam with as less as possible sidelobes, and bundling vertically as well.
    A good 3 element beam will do 6 dBd or in other words 100 watts in is 400 watts Effective Radiated Power to the front with still the same 100 watt feeding the antenna.

    Here some claims from a 3 element ham beam, much more realistic

    Yagi 3 element (dx-antennas.com)
     
    lonestarbandit likes this.

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