14-11-2012, 11:39 AM
Doordarshan Kendra Jaipur
Doordarshan.ppt (Size: 3.07 MB / Downloads: 54)
TELIVISON STUDIO
Studio floor
The studio floor is where production actually occurs. The studio floor is an open area, which contains the television cameras,' microphones, lighting equipments sets and crew.
Control room
The control room there is the programmer's director, assistant director, technical director, audio engineer and video engineer works
T.V. PICTURE
A picture can be considered to contain a number of small elementary areas of light or shade which are called picture element.
The scene is focused on the photo-sensitive surface of pickup device and a optical image is formed.
The photo electric properties of the pickup device convert the optical image to a electric image charge depending on the light & shade of the scene.
To transmit this information scanning is employed.
The horizontal scanning frequency is 15625 Hz. The vertical scanning frequency is 50 Hz.
The frame is divided into two fields, odd lines are scanned first and then the even lines are interlaced.
The frame is divided into 2 fields.
The field rate is 50 Hz. The frame rate is 25 Hz (field rate is same as the power supply).
MIXING
Mixing is an additive combination of two video sources.
Two input sources are mixed in proportion in a summing amplifier as decided by the position of the control fader.
Two extreme positions give either of the source at output. Middle of the two fader gives mixed output of the two sources.
The sum of two video sources is always 1 volt p-p.
WIPING
This is a non additive combination of two sources. A switching occurs during the active video at specific points on the raster to produces a pattern, between two video sources. Switching is controlled by an internal wipe pattern generator which can provide the waveform either saw tooth or parabola at H,V or both H and V rates. The very simple to very complex waveform can be generated by the wipe pattern generator.Simple patterns can be generated by logical combination of different waveforms However the production of more complex patterns is better handled by a microprocessor.
REQUIREMENTS
Antenna system
PDA’s
The most widely used narrow beam antennas are reflector antennas. The shape is generally a paraboloid of revolution.
For full earth coverage from a geostationary satellite, a horn antenna is used. Horns are also used as feeds for reflector antennas.
A small earth terminal, the feed horn is located at the focus or may be offset to one side of the focus.
Large earth station antennas have a sub reflector at the focus. In the Cass grain design, the sub reflector is convex with a hyperboloid surface, while in the Gregorian design it is concave with an ellipsoidal surface.