Add descriptions

02_text_description.md

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+Radar Text Descriptions for the Left Hand Text Field (Or on separate  monitor)
+
+The following four radar descriptions shall be applied to the left hand text description
+field:
+
+1. Chain Home radar
+   The UK developed the chain home radar in the 1940's. This was one of the earliest radar,
+   developed in response of threats of air attacks from the Germans. 
+
+   The scope is similar to that of an oscilloscope. One the horizontal axis of the scope is
+   the range. The vertical axis is the amplitude of the returned echo from aircraft.
+
+   The bearing of the incoming echo signal is detrmined by feeding the signals from two
+   identical dipole antennas, mounted at right angles to each other into a radiogoniometer.
+   The operator menually turns a search coil until the signal strengh on the oscilloscope
+   reaches a null poing (minimum signal). The direction (bearing) is read from a calibrated
+   dial.
+
+   In our exhibit, the chain home radar is located in Ventnor, on Isle of Wight.
+
+ 2. Marine a-scope
+    The UK, after developing microwave radar, which with it's shorter wavelengths,
+    became able to pick up echos from small targets such as the parascope and the
+    connong tower from enemy submarines.
+
+    The system consists of a steerable microwave dish connected to an oscilloscope
+    display. The horizontal axis is the range; the vertical axis is the strength
+    of the return; and the bearing (direction) is determined by manually rotating
+    the microwave antenna using a servo control at the console that drive servo motor
+    attached to the microwave dish antenns.
+
+    These radars were used on the Brittish Corvetts boats that were used in anti
+    submarine warefare.
+
+    In our exhibit, this radar is on a boat moored at the dock of the Community
+    Boating Center in Bellingham Bay.
+
+ 3. Marine Traffic Control Radar 
+
+    The marine traffic control radar is a plan position indicator (PPI) type radar,
+    where the display consists of a circular sweep beam. The range is determined by
+    how far the blip is from the center of the scope. The bearing is determined by
+    the direction of the beam in its rotation. The beam rotates clockwise staring
+    from north. The strength of the echo is determined by the brightness of the
+    blip on the scope.
+
+    All modern radars use this type of display.
+
+ 4. Police Boat Radar
+
+    The police boat radar is a plan position indicator (PPI) type radar, where
+    the display consists of a circular sweep beam. The range is determined by
+    how far the blip is from the center of the scope. The bearing is determined by
+    the direction of the beam in its rotation. The beam rotates clockwise starting
+    from the heading of the boat. A small line indicated which direction is north. 
+    the strength of the echo is determined by the brightness of the bliip on
+    the scope.
+