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OT: Tuning an antenna.

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  • OT: Tuning an antenna.

    I have one of those old directiional VHF antennas like we all used to have in my attic.
    remember when you had the fancy one with the dial controller so ya didn’t have to get up on the roof to go from ch3 to tune in ch9?
    anyway, current use is ota tv channels and fm radio.
    have a new? Fm radio station in the area that is a weak signal but a great station.
    i would like to turn the antenna to tune it in, but have long ago lost the box with the dial.
    any body know what voltage the turning Moter likes?

  • #2
    Some I've dealt with use 24 volts ac, that was fairly common at one time with those rotators. It could have been a 3 wire system, but mostly 4 wire. I'll see if I can remember how the hookup goes- that's been one long while ago since I put up an all-channel antenna with rotator. Channel Master was pretty common, I think Jerrold made one, Alliance made one, Automatic was another-What do you have?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #3
      If you know what's going on with the antenna, or where it's pointing as you tune it, you don't need the readout part that was in the control box. All you really need is to identify the common lead from the two hot leads, then alternate the 24 vac to either hot lead for direction control. It should be that easy.

      I don't quite recall- I think those things used about 30 watts or so. If you had a transformer that would give about two amps, that's probably enough power to make it run.
      Last edited by darryl; 11-24-2020, 01:29 AM.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        If I recall correctly, many of those antenna rotors used a device called a synchro. This was not a motor per se, but consisted of a rotor with a single winding and a stator with three. It combined the types of magnetic fields that you find in simple, single phase motors with the those in a three phase one. The control was identical (more or less) to the synchro that turned the antenna and they were connected with a four (plus ground/neutral) or five wire cable. AC was applied to both rotors and the synchro on the antenna followed, angle for angle, the position that the control was set to.

        In short, you had to have the correct control for the synchro on the antenna.

        Another type system used a resistor bridge (or similar) arrangement and a stepper style motor. The control had a series of resistors between fixed intervals and the motor on the antenna had the same. When the control was moved to a different position, the motor was stepped until it reached a matching position. Again, you had to have a control that matched the unit at the antenna.

        Both of these types of systems had mechanical stops to prevent the rotor from going around and around which would twist the antenna cable around the pole.

        24 VAC was probably one Voltage used, but you need the other connections as well.

        Antenna rotors are still sold. A call or e-mail to one of the dealers may be of some help here.

        https://www.bing.com/search?form=MOZ...=antenna+rotor
        Paul A.
        SE Texas

        And if you look REAL close at an analog signal,
        You will find that it has discrete steps.

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        • #5
          For one station only, direct it manually and leave it there.
          Helder Ferreira
          Setubal, Portugal

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          • #6
            Originally posted by Noitoen View Post
            For one station only, direct it manually and leave it there.
            That's too simple!

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            • #7
              Originally posted by darryl View Post
              Some I've dealt with use 24 volts ac, that was fairly common at one time with those rotators. It could have been a 3 wire system, but mostly 4 wire. I'll see if I can remember how the hookup goes- that's been one long while ago since I put up an all-channel antenna with rotator. Channel Master was pretty common, I think Jerrold made one, Alliance made one, Automatic was another-What do you have?
              No idea! Thanks for the reply’s, maybe I’ll play with it this weekend.

              Comment


              • #8
                These are available from about $45 to $130 complete. I saw an RCA programmable model for $96 on line. By programmable, I presume you could find the sweet spots for many stations then program them in so that you can return to them by selecting the saved positions. If its in the attic, probably last a lifetime.
                S E Michigan

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                • #9
                  If anyone is looking at getting one of the programmable RCA rotators, they have some quirks:
                  • More than once, pressing the reset button caused the unit to turn to 0° as it should, but then the rotator got stuck there. It wouldn't budge. Had to go up on the roof to un-stick it. Lubricating the gears with a lighter grease (or chain lube) seems to help so far.
                  • Over time, the motor has slowed so that the degree display no longer is synchronized with the actual rotation. The dirty secret of these units is that the degree display simply counts up or down at a set rate, there is no sensor & no direct link between the display reading and the antenna rotation. Over time, the display will drift so far off that you lose the ability to turn in one direction. The easy fix is to disconnect one wire to the rotator, hold the left or right button to run the display to the correct number, and then reconnect the wire. You're supposed to just hit the reset button, but this can cause the first issue.
                  Location: Northern WI

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