Understanding TV Signal Distribution Methods
Composite Signal TV (Composite Video)
The composite video signal includes several distinct parts:
- The video information in interlaced form.
- Pulses (not cleared) to return is visible.
- Line and field sync to maintain synchronism between the sender and receiver.
36 Shots and 12 Pauses
Antenna Signal
Cable attenuation + gain amplifier – gain attenuation cable + cable head-attenuation attenuation dealer-cable-attenuation step-step shunt-wire cable.
Distribution via Unique
It is most used in family or single-unit facilities. A single cable runs through the facility, and taps are placed by derivation. The last box type should be charged. Taps are selected with high attenuation at first, and with less attenuation at the end to match the levels on withdrawals.
Distribution with Distributors
It is most suitable for horizontal topologies or when there are many shots grouped. The signal emerges in hierarchical ways to reach the necessary number of shots. The elements of the same hierarchical level should have equal losses. If done in a symmetric structure, all taps have the same level.
Derivation Distribution
It is most appropriate for vertical topologies (multi-story buildings). These are vertical vias from which referrals are taken on each floor. The derivators are selected with higher attenuation and lower at the top end, to match the levels in plants.
Backbone Distribution
Suitable for large distribution areas such as housing estates. They consist of a high-capacity, low-loss via, which may even be optical fiber, carrying distributors or even leading to different technology terminals. From the main via, secondary roads are pulled to buildings or service areas.
Joint Distribution
The four distributions above are considered basic. In daily practice, combinations of these, called mixed distributions, are often used. One of the most widely used in buildings is the joint distribution by distributors and derivators.
General Characteristics of Amplifiers
- Gain Amplifier: The relationship between the level of the output signal and the input level in dB.
- Noise Figure: Indicates how much noise the amplifier adds to the input signal. The noise factor is the noise at K T0, and the noise figure is the value expressed in dB. Knowing the noise figure, we can calculate the Signal-to-Noise Ratio (SNR), and from this, whether the image quality is perfect.
- Bandwidth: 8MHz for single-channel amplifiers; one or more bands for broadband amplifiers.
- Input and Output Impedance: They are standardized to 75 ohms.
- Output Voltage: The maximum level that the amplifier delivers.
- Maximum Input Voltage: The maximum allowed level of input of the amplifier to avoid distortion.
LSL Calculation
LSL = 20 log(λ / (4πD)) = 78.02 dB
Why Higher Frequencies Attenuate More
Higher frequencies attenuate more than lower frequencies.
- With a power adapter that uses the cable itself to carry the current.
- To avoid impedance mismatch.
Satellite Dish Positioning Factors
- The direction and the azimuth.
- The longitude of the place of reception.
- The latitude of the reception.
- The longitude of the satellite.