Rotor to change antenna polarization?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KA5SDC, Sep 16, 2020.

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  1. KA5SDC

    KA5SDC Ham Member QRZ Page

    Is there a rotor that could be used to change polarization of a short (about 15 foot boom) yagi from horizontal to vertical? If so, this would eliminate the need for a second yagi to cover FM and SSB for 2m.


  2. WA7F

    WA7F Premium Subscriber QRZ Page

    Two choices:

    1. buy a second antenna
    2. get a cross polarized yagi with both vertical and horizontal elements.

    Ok, here’s number three:
    3. Waste a lot of time and spend a ton of money trying to axially rotate your one yagi.
    WD4ELG likes this.
  3. K6CLS

    K6CLS Ham Member QRZ Page

    the best SSB antennas do not have good SWR in the FM range. Better to buy another antenna.

    Although, yes folks have cobbled together some things that mostly work. Consider mounting your antenna on a hinge which will give the 90 degrees rotation; activate that with a linear actuator, like as used for Az on a polar mount satellite dish. funky but it works, sort of.
  4. W1VT

    W1VT Ham Member QRZ Page
    You may be able to locate an old Alliance U-100 rotator for this purpose.

    I recall reports of a 48 Yagi EME station in Southwick MA being able to work handheld stations in NYC on 446 MHz!
    Frank NC1I put together this 720 element array!

    Polarization rotation is very useful on 70cm EME, as without there are large periods of time in which the EME path is blocked to linearly polarized stations. When working DX, not hearing your own echos.

    Zak W1VT
    Last edited: Sep 16, 2020
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, the U-100 is a great choice (you'd have to find a used one) as the "boom" of the antenna can run straight through the rotator, which is then clamped to the mast. If a 15L beam is already assembled, some elements would need to be removed first and then reinstalled after running the boom through the rotator.

    This was a really common solution years ago.

    And rotating antenna polarity for EME work is also pretty common, going back to the seventies. If you look up Wayne Overbeck's (N6NB's) "cabover kilowatt" articles about operating from "four corners" and also operating from Alaska (he activated the first EME station in KL7, over 40 years ago), the photos show what he did there...rotating an array of 2m quad antennas to change polarity to whatever worked at the moment, and the entire array rotated on axis. I believe those articles are still on his website.
  6. NG1H

    NG1H XML Subscriber QRZ Page

    Another idea is to use a linear actuator as a radial arm. If it has internal limit switches then you don't even need anything other than a DPDT switch to control it. Make some bearings out of Teflon or nylon.
    WA4SIX likes this.
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Another approach, although not cheap, is just using a Yaesu G-5500 el/az rotator and instead of using the "el" part to elevate antennas (for satellite/EME work), just run the single antenna boom through the elevation rotator and let the rotator spin the antenna boom 90 degrees to go from H to V polarization. The "az" part is just a regular azimuth rotator, and the single control box allows full control of both motors.

    It works very well, I've used these, but they cost over $700 today.:(
  8. KA5SDC

    KA5SDC Ham Member QRZ Page

    I have purchased a Yaesu G-550 for this purpose. I have two Cushcraft 215WB antenna but mast space above my tower will be limited and there are antennas for other bands I also want to mount on this mast. I will mount one of the beams on a 25 foot mast first so it will be easier to experiment with. I will see if I can adjust for an acceptable SWR for both polarizations.

    Wish me luck!
  9. WA7F

    WA7F Premium Subscriber QRZ Page

    Good luck. It seems like having a rotor in the middle of the antenna boom would be an issue but, apparently others have done this. Post a picture and an update when you get it going.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    A friend of mine mounted his antenna to a door hinge, Then he had a rope attached to change polarity.

    Looked strange, But worked good and lasted a long time. :)

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