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# Lecture 1 Television Antenna. Parts of antenna.

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Lecture 1 Television Antenna

Parts of antenna

Formula Frequency 3,000,000,000 = =Wavelength in meters f= frequency in hertz

Wavelength Lambda (meters) Lambda (meters) Velocity (300,000,000 meters/sec.) Velocity (300,000,000 meters/sec.) Frequency (Hz) Frequency (Hz) = v/f = v/f

Antenna Systems Radio Energy in Space Radio Energy in Space –300 million meters per second E = MC 2 E = MC 2 Speed of Light Speed of Light

Wavelength conversion Meters: Lambda = 300/211.25 = 1.46 meters Miles: Lambda =.186/211.25 =.00088 miles Feet: 1 meter = 3.28 feet Lambda = 1.46 meters x 3.28 = 4.79 feet

Spectrum

TV Station WTHR-TV Ch.13 (210-216 MHz) WAVELENGTH IN: A.Meters B.Miles C.Feet

Types of Antenna Dipole

Vertical Plane Radiation Pattern

Monopole

Folded Dipole

Mobile antennas

Reflector Antenna

Yagi Antennas

Coax Linear Array

Single elements radiation pattern

Radio Waves Three important features of radio waves Three important features of radio waves –amplitude, frequency, and polarization Modulation by amplitude and frequency (AM and FM) is common Modulation by amplitude and frequency (AM and FM) is common Polarization Polarization –rarely used at all –essentially never to modulate

Polarization Polarization - the orientation of the electric field of an electromagnetic wave. Linearly Polarized Wave Circularly Polarized Wave

Won’t we pick up both signals? Polarization is related to antenna geometry Polarization is related to antenna geometry –Horizontal antennae won’t pick up vertical waves and vise versa Circular antennae Circular antennae –50% of linear waves –100% of a correctly oriented circular wave –none of a circular wave of opposite polarization

Current Uses of Polarization Satellite TV Satellite TV –Binary circularly polarized signal –Maybe PM Military communication--particularly air to sea communication Military communication--particularly air to sea communication –Circularly polarized FM signal

Antenna Design Sample Antenna Sample Antenna Basic Design Components Basic Design Components Equations Equations Calculations Calculations

Equations = c/ = c/ D =  D =  Gain in dB = 11.8 + 10 log(C 2 * n * S) Gain in dB = 11.8 + 10 log(C 2 * n * S) C=  for helical antennae C=  for helical antennae = wavelength = wavelength c = speed of light c = speed of light = frequency = frequency D = diameter of helix D = diameter of helix n = # of turns n = # of turns C = circumference C = circumference S = axial distance between turns S = axial distance between turns

Equations with Numbers = c/  x10^8 m/s)/(2.4GHz)=.125 m = c/  x10^8 m/s)/(2.4GHz)=.125 m D =  cm D =  cm S = 3.924 cm S = 3.924 cm n = 6 n = 6 Gain = 11.8 + 10 log(C 2 * n * S) = 7.46 dB for an antenna with approx. 4 cm diameter. Gain = 11.8 + 10 log(C 2 * n * S) = 7.46 dB for an antenna with approx. 4 cm diameter.

Antenna Safety Think before acting Think before acting Do not erect an antenna structure near enough to a power line allow distance between the two Do not erect an antenna structure near enough to a power line allow distance between the two Do not try to throw-in lead wire from one point to the another where there is even a remote chance of power line contact. Do not try to throw-in lead wire from one point to the another where there is even a remote chance of power line contact. Ground all antenna structures properly Ground all antenna structures properly Safety check receivers for power line leakage to the antenna. Safety check receivers for power line leakage to the antenna.

continuation Use standard antenna system connectors and equipment Use standard antenna system connectors and equipment Use power climbing equipment Use power climbing equipment Dress correctly hard hat rubber sole etc Dress correctly hard hat rubber sole etc Obtain help to handle heavy or hard manage equipment. Obtain help to handle heavy or hard manage equipment.

Experimentation TV Tuner Amplifiers Mixer Frequency Synthesizer IF filter Amplifier Envelope Detector Non-coherent detector prototype

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