PREPARATIONS FOR SOUNDING B2-7 
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JUDSON BIGELOW INC. U.S A. 
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Figure B2-2. Baseline-Check (four lead) With Hypsometer Check 
switching motor is on a separate switch, it will be turned on when the 
blower motor is turned on. The baseline-check should be completed as 
soon as possible after the battery voltages have reached their minimum 
values. When the temperature and humidity stabilize, tune the recorder- 
receiver to receive the radiosonde signal and adjust the controls for 
maximum signal strength and stability. 
5.2 Relative Humidity in the Baseline-Check Box. The relative hu- 
midity in the baseline-check box should fall ‘within the range of 30 to 40 
percent when the carbon hygristor is usedin the radiosonde. Should these 
limits be exceeded, the baseline-check humidity will be valid and used 
in the evaluation of that flight; however, as soon as the flight has been 
completed, the silica jel, magnesium chloride or the calcium chloride 
solution in the baseline-check box will be changed or renewed to bring 
the relative humidity in the box back within the 30 to 40 percent range. 
Silica jel is used as a drying agent to reduce the moisture in the box. 
The magnesium chloride solution absorbs moisture from the box when 
relative humidity is above 33 percent and evaporates moisture into the 
box when relative humidity is below 33 percent. When the calcium chlo- 
ride solution is used asahumidity control solution, the addition of more 
calcium chloride lowers the relative humidity and the addition of water 
raises the relative humidity. The door of the box should remain closed 
except when inserting or removing the radiosonde, or when the humidity 
control agent is being changed. 
1-1-69 FMH#3 
