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G8MNY  > TECH     12.11.23 09:05z 124 Lines 4815 Bytes #7 (0) @ WW
BID : 60178_GB7CIP
Subj: Rotator 12V /P
Sent: 231112/0904Z @:GB7CIP.#32.GBR.EURO #:60178 [Caterham Surrey GBR]

By G8MNY                                        (Updated Jun 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

This I built from an old Army 24V motor gearbox system & 360° AC pot, bought
new at rally many years ago. Although the same hardware may not be available
other homebrew solutions may make this information useful.

 _______________________                    Thread ║ ║ tube to fit
│ ┌───────────────────┐ │                bolt hole-║n║ inside /P pole
│ │  edgewise  meter  │ │                        __║~║__
│o└───────────────────┘o│                       │       │Rotator with
│     Left< o >Right    │                       │       │geared DC motor
└───────────────────────┘    5 Wire Cable       │_______│
                          with plugs & sockets  │_______│360° Pot
                                             flat base plate

                      Non locking centre
                    off change over switch
+12-15V >──┬────┬──────────o o o-0V
           │    │            \______________________*   *____ Rotator
           │   220R           ______________________*   *____ DC motor
          12R   │            /
           │    │       0V-o o o+12V                5 way
           │    │                                   Cable
          5V    ├─────┬─────────────────────────────*   *────┐
         Meter _│_   1K                                      │
         Lamp  /_\'   │                  .────.              │
           │  9V│    1K        10K      /large \            5K
           │    │   Preset<────Cal───┬─(centre 0)─┬─*   *──>Rotator
          5V    │ Zero pot    Preset │  \ meter/  │         Pot
         Meter  │     │              │   '────'   │          │
         Lamp   │    1K(not for a)   └───────┤├───┘          │
           │    │     │(normal meter)      100uF             │
    0V  >──┴────┴─────┴─────────────────────────────*   *────┘
                                               plugs & sockets

The simple circuit uses just a non locking change over switch to power the
under run low torque motor & gearbox, clockwise or anti-clockwise.

An under power rotator is useful for /P work as there is less chance of
damaging fouled cables or guys etc. My rotator can be left stalled with no
motor dammage, as it only draws 50mA.

Note, you do not normally need speed for aerial rotation so a well geared down
motor is best!

RF suppression of the motor may also be needed if you want to beam up on weak
signals, try adding caps like 1n, u1, 1u etc. across brushes & to motor chassis
as well as series chokes etc.

  │         │           │      │
  │ u1     === u1       ▀      │
 ===        ├────┐   <MOTOR>  === u1
  │     u1 ===  _│_     ▄      │
  │         │  ////     │      │

I do not earth the rotator through the control cable so there are no DC loops.
Mast earth is provided by a clip on a flexable lead to a ground stake if

My rotator pot was originally a 3 phase AC pot with 2 wipers & 3 pot taps,
which was reconfigured to a straight forward 360° track pot with no stops.

The pot is powered by a shunt regulated 9V supply. A large sensitive centre
zero meter is used (˝1mA), but a non centre zero one can also be used.

The meter is damped by a 100uF so that a scratchy rotator pot does not cause
wild readings. The zero preset pot sets the meter zero point (centre or side) &
the cal preset pot sets the full scale indication.

If a rotator is used with stops then a geared down normal pot (e.g. 270°) can
be used in the rotator & any unused track compensated for by this circuit.

My meter scale is marked.. as my rotator has no stops, so the needle swings
from SOUTH to SOUTH marks quickly on overturn.

   S    W    N    E    S

Physical calibration when portable is done by just lifting the rotator & mast
turning whole thing & putting it back down (a brain teaser as to which
direction!). Any tendency for the rotator to spin on the ground is solved
either by a few tent pegs into grass, or placed on a sponge sheet if on tarmac.

My system for this rotator uses a hole in the mast pole that allows a screw to
be put into a captured nut, in the inside of the smaller rotator tube.

    │  Mast   │
    │  Pole   │
    │         │
    ││ Tube  ││
    ││       ││
    ││  nut  ││ Mast
    │├───────┤│ Hole
    ││Wood   ││/
    ││      [│==Bolt
    ││   nut ││
/~~~~~~~│ │~~~~~~~\ Water shed
│~~~~~Rotator~~~~~│  Cover
│      shaft      │

Why Don't U send an interesting Bul?

73 de John G8MNY @ GB7CIP

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