video modulator

video modulator

A. OBJECTIVES:

· Measuring the frequency spectrum of video transmission
· Determine the carrier frequency range image and sound carrier frequency.
· Specifies the field width (bandwidth) on video transmission.
· Specify the type of modulation on the picture and sound.

B. EQUIPMENT USED:

· 1 Modulator video (VCD / VTR / video sender).
· A Spectrum Analyzer.
· An RCA cable connector - BNC.


C. CIRCUIT DIAGRAM:




How to emit (transmit) signal is amplitude modulated image similar to a radio broadcasting system that has been known. In both cases, the amplitude of a carrier wave radio frequency (RF) is made varies with the modulating voltage. Modulation is a signal of fundamental frequency (baseband). On television, this baseband signal is a composite video signal. Broadcast television is really such a radio system, but includes pictures and sound. Sound signal emitted by joining in it frequency modulation (FM) on a separate carrier wave transmitter in the same channel as the image signal.
Understanding the image signal is used here to mean a modulated carrier wave. The video signal is a signal to a picture tube. Video signal to television audio signal corresponds to the sound system. Details are clearer than the image signal AM (amplitude modulation picture) and an FM voice signal.




Figure 2.a shows the frequency spectrum of video transmission that produces an image signal comprising AM picture carrier frequency (center frequency) and sound carrier frequencies (frequency side of the upper and lower side frequencies) - without VSB, while Figure 2b shows the frequency spectrum in transmission generate video image signals of AM frequencies only have the upper side only (with VSB).

E. EXPERIMENTAL PROCEDURE:

1. Calibration Spectrum Analyzer to determine the reference spectrum.
2. Set-up instruments like in the picture above.
3. ON the instrument.
4. Measure the output video modulator (RF) using the Spectrum Analyzer and observe the frequency spectrum.
5. Image of the frequency spectrum.
6. Determine how much an image carrier frequency, carrier frequency sounds, and the difference frequency picture carrier and sound carrier frequency.
7. Observe the spectrum, determine the type of modulation used in transmission, by way of changing the freq. SPAN (reduced scale).
8. Figure spktrum frequencies multiples of the base frequency.