5/8ths Quad?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KB6LEE, Jul 21, 2021.

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  1. KB6LEE

    KB6LEE Ham Member QRZ Page

    New Tech wondering about building a 5/8ths cubical quad for 10m. I think Quads are supposed to be full wave antennas, but has anyone experimented with this? How would it affect T/O angle and ERP if just a simple driver and reflector arrangement. This could lead to a more Yagi like stack with a director or two? Anybody gone down this rabbit hole?
  2. WL7PM

    WL7PM Ham Member QRZ Page

    There is some evidence to recommend a 5/4 th wavelength horizontal loop.
    For local-regional comms out to 800 miles or so, a circumference around 300 feet seems to work VERY well on 75 meters, comparing favorably to 2 wave loops and in some conditions out-performing one wavelength loops at comparable heights.
  3. EA1DDO

    EA1DDO Ham Member QRZ Page

  4. M0AGP

    M0AGP Ham Member QRZ Page

    Interesting idea. Half wave dipole is to extended double Zepp (5/8 wave per leg), as one wavelength quad loop is to …?

    1/2 —> 5/4

    1 —> 5/2

    So the quad version of an EDZ is a 5/2 wave loop…?

    Seems not: the max gain of a loop is 1.5 wavelengths. Or does that curve go back up again when we hit 2.5 wavelengths?

    Not sure the 1dB gain in a 1.5 wavelength loop is worth the hassle of matching it.

    This was surely known in the 1930s, right?
  5. W1VT

    W1VT Ham Member QRZ Page

  6. W1VT

    W1VT Ham Member QRZ Page

    Forty years ago I had little difficulty getting a 2 element 2 band Quad to work--made out of bamboo and supported by left over construction materials.

    Full wave Quad loops are nice because they are an easy 50 ohm feed and work reasonably well without a balun.
    Now we have wonderful tools like the NanoVNA that could be used to build more sophisticated antennas.
    Someone with too much time on their hands can custom design baluns using the scraps they have on hand now that inexpensive measurement tools are available.
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    Multi-element (Yagi-like) arrays with one driven element and several parasitic elements rely on the parasitic elements being "resonant" for induction to create the required currents (at just the right relative phase) to make the array directive.

    Each element would have to be "driven" if the elements are not intrinsically resonant (~0.5wl or ~1wl) at some specific frequency of use.
  8. W1VT

    W1VT Ham Member QRZ Page

    Another approach may be to use wireless technology to monitor and modify the parasitic elements as needed.
    M0AGP likes this.
  9. RW4HFN

    RW4HFN Ham Member QRZ Page

    Sorry, I'll clarify. To CONTROL what the modelers are modeling... What is the criterion? Gain? It's a matter of 2 minutes to check the reinforcement of a particular frame configuration... The table above is generally correct, but the figures are not always accurate, according to MMana.
  10. M0AGP

    M0AGP Ham Member QRZ Page

    Actually I was thinking about this as a way of controlling a very flexible parasitic array: the base of each vertical can have a state of driven, inductor, capacitor or open circuit, corresponding to an element becoming a driver, reflector, director or deactivated, respectively.

    You can imagine 4 rows of 4 elevated verticals… you would sort of get the vertical equivalent of a stack of 4 yagis, each with 4 elements, but electrically steerable.

    If the pattern is too sharp, deactivate the middle two rows so you only have 8 elements in your vertical yagi.

    Sort of like the Garden Beam but on steroids, and steered electrically.
    Last edited: Jul 21, 2021

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