Ham IV - Works Normally But Only Through 160 Degrees of Arc

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by VE4LS, Dec 5, 2017.

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  1. VE4LS

    VE4LS Ham Member QRZ Page

    Hello Folks:

    I have an interesting one.

    Tower work done a few days ago to correct loose mast to rotor fitting. Nuts tightened, and the Wilson System One worked through a full 360 degrees nicely for a day of maybe 6 rotations, then it was parked overnight at full clockwise to North plus a few degrees which is where the clearance is maximum between the elements and a tree branch.

    Next day, I moved the antenna counterclockwise to North to test for tree branch clearance, then when coming back clockwise through 160 degrees, the rotation stopped. It will react fully normally for any function clockwise or counterclockwise through the 160 degree range, but will not go clockwise past a beam heading of 160.

    This is about 2 years old and purchased exchanged Ham IV from a reputable re-builder and not many operating cycles on it.

    Any suggestions as to what has happened and what to do about it?

    Thanks for taking the time to help out.

    73 de Lee VE4LS

    Attached Files:

    Last edited: Dec 5, 2017
  2. KI7LGN

    KI7LGN Premium Subscriber QRZ Page

    Bad position sensing pot, maybe a bit of grit or debris got knocked loose inside the rotor when you where up there working on it???


  3. VE4LS

    VE4LS Ham Member QRZ Page

    Its not just an indication of not moving past 160 degrees, the rotor stops .... as if it had hit the clockwise limit switch at 160 instead of 360 plus maybe another 10 degrees as is normal.

    Lee VE4LS
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Make sure the rotating mast or the coax cable loop isn't binding on something.

    You might ask someone else to use the rotator control while you look carefully up top using binoculars to assure nothing is binding or cable being snagged by something, etc.
  5. VE4LS

    VE4LS Ham Member QRZ Page

    Good suggestion ..... we are having a storm now, but I will get my drone out and have a look when the weather calms down.

    A drone is an excellent tool for tower inspection and it can record various views.

    Cheers folks!

  6. VE1CZ

    VE1CZ Ham Member QRZ Page

    Lee I just had this happen to me last week,I found a bad limit switch inside the rotor,contacts were dirty.You will need to take it apart,messy job but easily fixed.Bob VA6PPZ/VE1CZ
  7. VE4LS

    VE4LS Ham Member QRZ Page

    Thanks Bob ...... it reacts just as if that happened .... and I think I may have thrown things off by leaving (maybe) parked against the full clock-wise limit switch.

    Anyway, I have the previous rotor which was removed from service because of a faulty direction indicator pot and thought after more than 20 years service that getting it rebuilt would be a good precautionary move in anticipation of retirement. As it turned out, due to shipping costs, it was more effective to just buy a rebuilt rotor rather than sending there and back.

    So as soon as I can find a spot with the new pot and a plastic bearing race, I will do the overhaul myself, then have the "new" rotor removed and the "old-old" rotor reinstalled.

  8. WA8UEG

    WA8UEG XML Subscriber QRZ Page

    If it was rebuilt by a reputable person or even someone that knows a little about how rotors operate I would go with WIK's suggestion. Sounds like its binding or the cable is caught up. If your using a thrust bearing I would really suspect a binding problem especially if you did not shim a 2" mast onto the rotor.
  9. WB2MJG

    WB2MJG Premium Subscriber QRZ Page

    You can test whether its the limit switch by jumpering it out I believe. But test carefully!
  10. VE4LS

    VE4LS Ham Member QRZ Page


    That looks like a good test that can be performed to confirm the problem in the decision process before removal and exchange of rotors.

    It appears that jumpering pins 1 and 5 will bypass the clockwise limit switch. Pins 1 and 6 will bypass the counter-clockwise limit switch.

    If I can get home before dark I'll refresh my drone flying skills and then do a "ground-based inspection" of the feedline to see if it is hanging up and stopping the rotation. Also, the mast diameter is 2" and alignment between the thrust bearing and output of the rotor is very good and rotated smoothly for several full cycles around the compass rose with the tower guy" on the tower watching it function.

    Thank-you everyone so far, you've been very helpful and it is appreciated greatly.

    Next report will come after I take some video and/or stills of the top of the tower.

    Cheers folks!

    Lee VE4LS

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