Before launching the radiosonde, bend the sensor boom to the correct sounding position using the unwinder pin. This also attaches the radiosonde to the unwinder and the balloon.
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Take the radiosonde to your left hand.
- Press the top part of the fastener with your left thumb and at the same time press the other side of the fastener with your other left hand fingers.
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Take the unwinder to your right hand.
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Start pushing the unwinder pin along the groove.
Make sure that you keep pressing the top part of the fastener with your left thumb and the other side of the fastener with your other left hand fingers. 
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Start pushing the unwinder pin along the groove.
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As you push the unwinder pin with your right thumb, the unwinder pin pushes the sensor
boom to the bent position. You must push the unwinder pin until the sensor boom is bent to
45 degrees and the unwinder pin is firmly locked to its place.
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Make sure that you pressed the unwinder pin fully to its position as shown in the
following figure.
The edge of the unwinder pin and the edge of the part under it must be in line with each other.