Modulator VIDEO

Objectives:

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


Equipment Used:

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


Circuit diagram:

Basic Theory:
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).

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.


Question:

1. What system is used in the video modulator?
2. From step 6, how to know what types of modulation?

Experimental results:

 

Gambar Spektrum Frekuensi	Keterangan
	Ref = 102dBµ BW = 100 KHz CF = 5 MHz CP1ΔF + 4,32 MHz 2 MHz / DIV ΔV + 18,8 dB Frekuensi Pembawa Gambar : LSB = 5 MHz - 4,32 MHz USB= 5 MHz + 4,32 MHz Frekuensi pembawa suara : tidak dapat dilihat dengan spectrum analyzer karena frekuensi sangat kecil
	Ref = 102dBµ BW = 100 KHz CF = 214 MHz CP1ΔF + 4,32 MHz 2 MHz / DIV ΔV + 18,8 dB Frekuensi Pembawa Gambar LSB = 214 MHz -  4,32 MHz USB= 214 MHz + 4,32 MHz Frekuensi pembawa suara : tidak dapat dilihat dengan spectrum analyzer karena frekuensi sangat kecil
	Ref = 102dBµ BW = 100 KHz CF = 421 MHz CP1ΔF + 4,32 MHz 2 MHz / DIV ΔV + 18,8 dB Frekuensi Pembawa gambar : LSB = 421 MHz - 4,32 MHz USB= 421 MHz + 4,32 MHz Frekuensi pembawa suara : tidak dapat dilihat dengan spectrum analyzer karena frekuensi sangat kecil
	Ref = 102dBµ BW = 100 KHz CF = 624 MHz CP1ΔF + 4,32 MHz 2 MHz / DIV ΔV + 18,8 dB Frekuensi Pembawa Gambar : LSB = 624 MHz - 4,32 MHz USB= 624 MHz + 4,32 MHz Frekuensi pembawa suara : tidak dapat dilihat dengan spectrum analyzer karena frekuensi sangat kecil
	Ref = 102dBµ BW = 100 KHz CF = 831 MHz CP1ΔF + 4,32 MHz 2 MHz / DIV ΔV + 18,8 dB Frekuensi Pembawa Gambar : LSB = 831 MHz - 4,32 MHz USB= 831 MHz + 4,32 MHz Frekuensi pembawa suara : tidak dapat dilihat dengan spectrum analyzer karena frekuensi sangat kecil
	Ref = 102dBµ BW = 100 KHz CF = 1055 MHz CP1ΔF + 4,32 MHz 2 MHz / DIV ΔV + 18,8 dB Frekuensi Pembawa Gambar : LSB = 1055 MHz - 4,32 MHz USB= 1055 MHz + 4,32 MHz Frekuensi pembawa suara : tidak dapat dilihat dengan spectrum analyzer karena frekuensi sangat kecil

Picture Frequency Spectrum

LSB = 5 MHz - 4,32 MHz

USB= 5 MHz + 4,32 MHz

Picture Carrier Frequency:

Voice carrier frequency: can not be seen because of the frequency spectrum analyzer with very small

DATA ANALYSIS:

1. Viewed from the image spectrum that we get can we know that the value of
Carrier frequency: 421 MHz
CP1ΔF + 4.32 MHz
Then:
USB = 421 MHz + 4.32 MHz = 425.32 MHz
LSB = 421 MHz - 4.32 MHz = 416.68 MHz
Voice carrier frequency: can not be seen because of the frequency spectrum analyzer with extremely small compared with the frequency carriernya.
2. For frequencies multiples:
• Frequency of multiples of 1 in: 5 MHz
• Frequency of multiples of 2 on: 214 MHz
• Frequency of multiples of 3 on: 624 MHz
• Frequency of multiples of 4 at: 813 MHz
• Frequency of multiples of 5 in: 1055 MHz

ANSWER QUESTIONS:
1. Modulation system used in the video are AMPLITUDE MODULATION, because the signal amplitude information affect the amplitude of the carrier signal, the signal information into the cover of the carrier signal.

A common use of signal Am is: AM radio broadcasting is widely used for broadcast AM radio wave signal, the TV picture (Video), Radio communication: aircraft, amateur radio (SSB), CB radio (Citizens Band Radio 􀂶). Digital data transmission: Modems Computers (combination with QAM modulation)

2. Known types of modulation are amplitude modulation can be seen from the changes in amplitude and has a spectrum of AM.
Based on the equation of the spectrum signal modulated AM AM will have 3 (three frequencies):
• fc: carrier frequency signal
• LSB: Lower Side Band frequency (LSB), namely the difference frequency carrier signal and the signal information.
• USB: Upper Side Band frequency (USB) is the number of carrier signal frequency and signal information.

CONCLUSION
1. In a video modulator that is used is amplitude modulation Modulation (AM)
2. AM modulation is shown on a spectrum analyzer displays the three frequencies namely
- carrier frequency (fc)
- Frequency of Lower Side Band (LSB)
- Frequency of Upper Side Band (USB)
3. The difference between USB and LSB frequencies are = 4.32 MHz
4. Used 100 KHz bandwidth