Satellite TV and Field Strength Measurement

Posted on Feb 8, 2025 in Other subjects

Field Strength Meters

Meters are devices for measurement and analysis, including bookmarks and digital terrestrial TV. They cover the following bands: FI satellite, VHF, UHF, hyperband, and cable television channels (E). Frequencies range from 48 MHz to 2050 MHz. The input impedance is 75 ohms, and the maximum signal is 130 dBµV. They are equipped with a 12V battery.

Field Strength Measurement

The first step to installing an antenna is to calculate the field strength of the site.

Procedure:

  • Connect the coaxial cable from the antenna to the field strength meter.
  • Select the frequency using the controls.
  • Read the signal level on the display.
  • Use the attenuator to achieve a reading within the appropriate margins.

Carrier Signals:

  • Video Carrier: Often represents the video signal module (PM).
  • Audio Carrier: Frequency modulation of the audio signal (FM).

UHF = Ultra High Frequency

Modules: Antenna, communications, energy, service drive.

Frequency Bands:

  • C-Band (3.7 to 4.2 GHz)
  • Ku-Band (10.75 to 12.75 GHz)

Azimuth: The horizontal angle measured is formed by rotating the reflector around its axis with respect to the south, when orienting towards the point where the equator is located on the satellite.

EIRP: Equivalent Isotropically Radiated Power.

Parts of a Satellite TV Antenna:

  • Support
  • Reflector
  • Focus
  • Clamping Rod
  • Reflector Adjustment Screws
  • Boom
  • Base

Focus Types:

  • Centered
  • Offset
  • Cassegrain (consisting of two reflectors)

Satellite TV Antenna Characteristics:

  • Gain
  • Bandwidth
  • Directivity
  • Focal Value-Diameter (F/D ratio, representing the curvature of the reflector)
  • Performance (the relationship between incident energy and energy the focus captures)

Antenna Pointing to a Satellite:

Requires adjusting the azimuth and elevation (angle of the reflector axis on Earth).

Latitude: The distance from a point on the Earth’s surface to the Equator.

Longitude: The distance from a place to a meridian.

Meridian: Any of the great circles of the Earth that pass through both poles.

DiSEqC: Communication protocol.

Use of this feature: Automatic mode to finish accurately aiming the antenna.

Antenna Alignment Tools:

  • Inclinometer: Precision instrument for measuring the elevation angle.
  • Compass: Precision instrument for measuring the azimuth.
  • Meter: Measures the signal level and the quality of the received images.

Mobile Antenna Orientation (Polar Mount):

  • Orient the antenna south using a compass.
  • Adjust the inclination of the polar axis to match the latitude of the receiving location.
  • Adjust the declination angle appropriately.
  • Point the antenna towards the desired satellite.

Feeder: Collects the signal reflected by the antenna and guides it through a waveguide to a converter.

LNA: Low Noise Amplifier.

Converter: A device that converts the signal from a Ku-band frequency to an IF (Intermediate Frequency) to send it to the receiver via coaxial cable.

Parts of the Converter:

  • LNA Amplifier
  • Mixer
  • Local Oscillator
  • Intermediate Frequency Filter

Signal Quality Metrics:

  • C/N (Carrier-to-Noise Ratio): Quality before modulation.
  • S/N (Signal-to-Noise Ratio): Quality after modulation. S/N: Signal Power / Noise Power > 43 dB.

Microprocessors work with 64-bit architecture.