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G8MNY  > TECH     10.11.23 08:55z 87 Lines 4526 Bytes #5 (0) @ WW
BID : 60058_GB7CIP
Subj: Rotator Radio Shack info
Sent: 231110/0822Z @:GB7CIP.#32.GBR.EURO #:60058 [Caterham Surrey GBR]

By G8MNY                                       (Updated Jan 15)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

This is similar to the Hishmann Hit Ro 250 offset rotator, with an unusual
rotator control system with no electronics (2 diodes) but to solve the sync
issue it uses a pulsed speed feedback system. The controller has a movable
control plate with 3 switches on it. The mains is fed via slip rings to the off
home contact! And it uses a pulsed DC motor as a control servo.

                                                Stub Clamp
          _______________                    =³__³=
        ./-------------/ |                 __³____³___
    _.-'.- _"  `;  _.-'   |               /         )====)
 .-'   \__ . - ".-'        |  4 Wire     ³         ³   Mast Clamp
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´        _.:|   Cable     À¿         )====)
³              ³  _..-:'-'"               ÀÄÄÂÄÄÄÄÂÙ
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁ:'-"'                        =³__³= Stub Clamp
     CONTROLLER                      ROTATOR

The rotator has split phase AC squirrel cage motor & a DC motor in the
controller. The series AC capacitor gives a 90ø leading voltage into either of
the windings determining the direction of the rotator motor. In the controller
a chain of gears turns the switch plate. In the rotator 1 gear & a worm drive
gives the same gear ratio to the well greased up stub mast champ tube from the

Both motors need regular servicing to move grease around & stop rusting in the
outside rotator etc.

DIAGRAM                                        CAM          CAM
                                             SWITCH        SWITCH    AC ROTOR
            x ,              x oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÂÄÄ* 3 *ÄÂÄÄÄÄÄÄÄÄ¿ MOTOR
LÄoÄÄoÄÂ>(Äo/' oÄ)<¿  ÚÄÄÄÂÄoÄÄ> ÚÄ´<ÃÄo x      o   ³        o        ())))Ä¿
  Fuse ³    NOT    )º(    ³    o ³      <ÄÄoÄoÄÄ>  ===120uF   <ÄÄoÄ¿  ===== ³
       ³   HOME    )º(    ³    ³ ÃÄ´>³Äo        o   ³        o     ³  ())))Ä´
       ³           )º(    ³     27R                                ³    6R  ³
                    ³ ³  LAMP    ³   ____    ³                 5W           ³
                    ³ ³   ³      ³  /DIAL\   ³                              ³
                    ³ ³   ³      ÀÄ´MOTOR ÃÄÄ´                              ³
                    ³ ³   ³         \.__./   o ³ CAL          R O T A T O R ³
                    ³ ³   ³                  o ³ BUTTON                     ³

 x = Indicator Plate Switches,  >( )< = Slip Rings,   * = External Connection

On moving the control knob & plate the switches power the rotator (lamp comes
on). Low voltage AC of the right phase direction is passed to the split phase
rotator motor & DC of the right polarity is selected for the dial motor.

The dial plate above the control plate that carries the lamp, is moved around
by the DC pulsed dial motor. The "on" time of this motor just enough to make
its' own cam stay in step with the rotators' cam. The 2 Rs around the dial
motor ensure start up & decay speed are right to maintain about 50% duty power
on cycle so there is plenty of pulse width control to ensure the dial stays in

When the dial plate agrees with the control plate the home contact turns off
the power & the lamp goes out.

As it is possible to get this type of servo feedback out of step, a calibrate
button is provided underneath the controller. If the controller fails to power
off after rotating this usually means the rotator has reached its mechanical
stop & is not providing any more servo pulses. Pressing the Calibrate button
then runs on the dial motor to catch up so the controller powers off OK.

Calibration should not be done often (once/10mins?) as it applies much higher
voltage to the DC motor & heats up the 27R & the stalled rotator motor. Also
the rotator motor itself is too hot to touch after doing this just once!

As with other rotators, the AC motor is well over run, so if more than 2 mins
use is needed, add a high wattage R (80R 10W) in series with neutral will
increase rotator motor run time before it overheats & burns out. This also
reduces the lamp power & increases it's lifetime too.

Why Don't U send an interesting Bul?

73 de John G8MNY @ GB7CIP

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