rotatable phased array

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KU7I, Nov 4, 2017.

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  1. KU7I

    KU7I Ham Member QRZ Page

    The Theory: Two identical 2 element vertical parasitic arrays spaced a half wave apart fed in phase. But rather than the whole array rotating as one system each 2 element array rotates on its own axis in sync with the other so they both always point at the same direction at the same time. This would work when they are both firing perpendicular to their axis but what about all of the other directions when one antenna starts to fire towards the other or vice versa?

  2. AC6LA

    AC6LA Ham Member QRZ Page

    Not exactly the scenario you described but a few years ago I modeled two horizontal 2m 5L Yagis, each at 1.5 λ above real/average ground, fed in phase, separated horizontally by 1.5 λ, with each antenna being rotated by the same azimuth angle. The geometry looks like this.

    And here is what the azimuth pattern looks like at 9° elevation as the rotation angle is varied from 0° to 90°. The outer ring has been frozen so you can see the difference in gain as well as the difference in pattern shape. In the lower-right corner of each frame, variable "D" shows the rotation angle.


    Complete details here (third bullet).

    Dan, AC6LA
    KF6A, K5URU, AK5B and 1 other person like this.
  3. KU7I

    KU7I Ham Member QRZ Page

    Wow, thank you for that Dan. Very insightful. Lucky for me my main areas of interest lie to the southwest (VK/ZL, pacific) and to the Northeast from me and these two areas are the two directions that are perpendicular to the boom almost exactly 90 degrees. My plan is to be able to switch in and out the second, identical array as needed. Sort of like when you work those guys on 20 meters who have a pair of stacked mono banders and they can switch in and out between the top beam, the bottom beam, or run both in phase. I would be doing that with these two antennas but instead of a vertical stack they are a horizontal stack with each antenna sitting on its own rotor.

    Very very helpful post. Thanks again.

  4. KU7I

    KU7I Ham Member QRZ Page

    Just re-read your post, why 1.5 wavelengths spacing?

  5. AC6LA

    AC6LA Ham Member QRZ Page

    The boom length for the 2m Yagi in the example is ~0.66 λ so that constrains how close the spacing can be. For a discussion of the results with spacings from 0.75 λ to 4.0 λ see the last part of the third bullet here

    following the words "I then wanted to see what would happen if the spacing between the towers was changed."

    Dan, AC6LA
    KF6A and AK5B like this.
  6. KU7I

    KU7I Ham Member QRZ Page

  7. AA7EJ

    AA7EJ Ham Member QRZ Page


    I am still working on my Electronically Steerable Array - ESA.
    For simplicity I am going to use 3 verticals spaced in 1/8 wavelength triangle.
    I am still working on hardware and software.

    Next part of the project is to "analyze" the array to see how the radiating pattern looks when phases of the SAME signal are changed in each antenna. ( Perhaps I should have done this first...o well...).

    I am using MMANA and know how to control each antenna phase.
    After seeing your post here I am wondering how you managed to have graphical display (on one plot) while varying antennas "rotation" angles.

    At preset I will end up with EACH phasing setup as a SEPARATE model.
    Will do , but...

    Ideally I like to be able to pass the phasing angles as parameters to "master analysis" application for "system " radiation pattern display.

    Perhaps MMANA cannot even do similar wiring configuration (rotating Yagis) as you have done?

    73 Shirley
  8. AC6LA

    AC6LA Ham Member QRZ Page

    AutoEZ, EZNEC, 4nec2, and AM by Teri Software all have the ability to "capture" an azimuth or elevation radiation pattern as a separate trace. Then you can modify the model, recalculate, show the new pattern , and overlay the captured trace.

    I don't know how to do something similar with MMANA but I am not very proficient with that program. Perhaps one of the MMANA super-users like Nick, UA3TW, can offer a suggestion. His email address is shown on his QRZ profile.

    Dan, AC6LA
    KF6A likes this.

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