Telek0munikasi: PATTERN GENERATOR

PATTERN GENERATOR

Objectives:

1. Getting to know the basic patterns in the Pattern Generator.

2. Measuring standard composite video and voltage on each pattern.

3. Measuring on the modulator wave modulated video (RF).

4. Measuring video IF.

Equipment Used:

1 Pattern Generator TV signal, LODESTAR CPG-1367A

1 Oscilloscope 40 MHz and passive probe

1 Power Supply

A cable connecting the BNC - BNC 75 

A BNC connector cable - RCA 75 

1 T-BNC Connector

Figure 1. Pattern Generator

Theory Platform:

Source of image patterns (pattern generator) is the technique of video (television) for the purpose of setting up or finding fault. There are various kinds of image patterns with a variety of needs. Pattern of so many images that exist, there are several commonly used image patterns are not very specific uses.

Types of Image and its Use Patterns :

a. Spots (Dot)

To check and adjust the static convergence in the middle of the screen with a low brightness. This should be done according to the television manufacturer's instructions.

b. The boxes (crosshach)

Plaid pattern with horizontal lines and vertical lines with the background color of black and white color line.
1. To check and adjust the horizontal and vertical dynamic convergence and the convergence angle.
2. By linearity of deflection (deflection) the correct horizontal and vertical, horizontal white lines should be a rectangular equilateral. If not, then the plane can be checked for truth response amplitudes. Vertical white line width should be 200 ns. If this line is not sharp and visible lower intensity than the horizontal line, the amplitude response is possible recipient is not enough. If vertical lines appear double, receiver circuit may be vibrating.
3. To pin-cushion proofreaders check the receiver. With the convergence of the right, square in the corner of the screen should be approximately equal to a square in the middle of the screen at a distance of normal vision.

c. White

This pattern contains a signal 100% white (without color information) with alternating burst.
1. Images for constant brightness on the entire screen (tida no hum, etc..)
2. Color picture tube for setting a good white (white-D).
3. Limitation of fire flow on the color picture tube.
4. For the video recorder is ideal pattern for the current setting of writing (recording) luminance. This pattern can also to set the FM demodulator (setting white level).

d. Beam Color (color)

Blocks of colors (color bar) consists of 8 vertical color bar standard and a reference beam horizontally. Beams 8 colors are arranged in order of depreciation luminan. From left to right beams D color is white, yellow, cyan, green, magenta, red, blue, and black.
This pattern is used to set the operational control of the receiver at the correct position.
Horizontal beam (white level) on the bottom of this pattern is used as a standard when setting the amplitude signal of color differences with relationships with luminan signal in the picture tube. Signals can be used for resetting the signal amplitude of the demodulator circuit and the matrix, as the output can be compared with the reference beam. In addition to the above purposes, this pattern can be used to check the overall color appearance. So can also be used checks and settings on the receiver or VCR:

1. Lock Inspection burst.
2. AGC examination of color and which create the color.
3. Examination series reactance of the subcarrier regenerator.
4. Examination of the regenerator subcarrier synchronization.
5. Checking circuit identifier (identification) PAL.

Signal Synchronization

Synchronization signal is a signal that is always given periodically and remains, serves to drive a raster scanning path in every television set so that the formation of the video signal into an image and the exact arrangement will remain the same as the original position in the field of raste
camera (picture production), therefore the synchronization signal is always supplied along with the video signal sent anywhere. For the formation of this raster scanning system will require two kinds of synchronization are:
- Namely the horizontal synchronization signal to the horizontal scanning provided at each horizontal retrace.
- Vertical sync signal is for vertical scanning provided on each vertical retrace.

Figure 2. sync signal

Figure 3. composit video signal

Video signal which is equipped with synchronization signals called the complete video signal (Composite Video signa / CVSl), while for color video signal is called Color Composite Video Signal (CCVS). Because the video signal has been added color information signals, ie signals and signal Burst Color Sub Carrier.

Experimental Procedure:

Set-up equipment such as in the picture above.
Connect the pattern generator with the power supply 8, 5 V, then ON the instrument.
Pattern generator output switches on and observe put on VIDEO waveforms for each pattern.
Observe and picture synchronizing signal and horizontal blanking, vertical blanking, front and rear porch, and image information of each pattern.
Images and specify voltage waveforms.
Pattern generator output switches on and observe put in the IF waveform for each pattern and the measuring frequency.
Image of the wave form and specify voltage.
Image signal for one frame (still image) in composite video, determine the level and the perioda.