lecture 1 television antenna. parts of antenna
TRANSCRIPT
Lecture 1Lecture 1
Television AntennaTelevision Antenna
Parts of antennaParts of antenna
FormulaFormula
Frequency
3,000,000,000=
=Wavelength in metersf= frequency in hertz
WavelengthWavelength
Lambda (meters)Lambda (meters)Velocity (300,000,000 Velocity (300,000,000
meters/sec.)meters/sec.)Frequency (Hz)Frequency (Hz)
= v/f= v/f
Antenna SystemsAntenna Systems
Radio Energy in SpaceRadio Energy in Space–300 million meters per 300 million meters per secondsecond
E = MCE = MC22
Speed of LightSpeed 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
SpectrumSpectrum
TV StationTV Station
WTHR-TV
WTHR-TV
Ch.13 (210-216 MHz)
WAVELENGTH IN:
A. Meters
B. Miles
C. Feet
Types of AntennaTypes of Antenna
Dipole
Vertical Vertical Plane Plane
Radiation Radiation PatternPattern
MonopoleMonopole
Folded DipoleFolded Dipole
Mobile antennasMobile antennas
Reflector Reflector AntennaAntenna
Yagi AntennasYagi Antennas
Coax Linear Coax Linear ArrayArray
Single elements radiation Single elements radiation patternpattern
Radio WavesRadio Waves
Three important features of radio Three important features of radio waveswaves– amplitude, frequency, and polarizationamplitude, frequency, and polarization
Modulation by amplitude and Modulation by amplitude and frequency (AM and FM) is commonfrequency (AM and FM) is common
PolarizationPolarization– rarely used at allrarely used at all– essentially never to modulateessentially never to modulate
PolarizationPolarization
Polarization - the orientation of the electric field of an electromagnetic wave.
Linearly Polarized Wave Circularly Polarized Wave
Won’t we pick up both Won’t we pick up both signals?signals?
Polarization is related to antenna Polarization is related to antenna geometrygeometry– Horizontal antennae won’t pick up vertical Horizontal antennae won’t pick up vertical
waves and vise versawaves and vise versa Circular antennaeCircular antennae
– 50% of linear waves50% of linear waves– 100% of a correctly oriented circular wave100% of a correctly oriented circular wave– none of a circular wave of opposite none of a circular wave of opposite
polarizationpolarization
Current Uses of PolarizationCurrent Uses of Polarization
Satellite TVSatellite TV– Binary circularly polarized signalBinary circularly polarized signal– Maybe PMMaybe PM
Military communication--Military communication--particularly air to sea particularly air to sea communicationcommunication– Circularly polarized FM signalCircularly polarized FM signal
Antenna DesignAntenna Design
Sample AntennaSample Antenna Basic Design ComponentsBasic Design Components EquationsEquations CalculationsCalculations
EquationsEquations
= c/= c/ D =D = Gain in dB = 11.8 + 10 Gain in dB = 11.8 + 10
log(Clog(C22 * n * S) * n * S) C= C= for helical for helical
antennaeantennae
= wavelength= wavelength c = speed of lightc = speed of light = frequency= frequency D = diameter of helixD = diameter of helix n = # of turnsn = # of turns C = circumferenceC = circumference S = axial distance S = axial distance
between turnsbetween turns
Equations with NumbersEquations with Numbers
= c/= c/x10^8 m/s)/(2.4GHz)=.125 mx10^8 m/s)/(2.4GHz)=.125 m D =D = cm cm S = 3.924 cmS = 3.924 cm n = 6n = 6 Gain = 11.8 + 10 log(CGain = 11.8 + 10 log(C22 * n * S) = 7.46 dB for an * n * S) = 7.46 dB for an
antenna with approx. 4 cm diameter.antenna with approx. 4 cm diameter.
Antenna SafetyAntenna Safety
Think before actingThink before acting Do not erect an antenna structure near Do not erect an antenna structure near
enough to a power line allow distance enough to a power line allow distance between the twobetween the two
Do not try to throw-in lead wire from one Do not try to throw-in lead wire from one point to the another where there is even a point to the another where there is even a remote chance of power line contact.remote chance of power line contact.
Ground all antenna structures properlyGround all antenna structures properly Safety check receivers for power line Safety check receivers for power line
leakage to the antenna.leakage to the antenna.
continuationcontinuation
Use standard antenna system Use standard antenna system connectors and equipmentconnectors and equipment
Use power climbing equipmentUse power climbing equipment Dress correctly hard hat rubber sole Dress correctly hard hat rubber sole
etcetc Obtain help to handle heavy or hard Obtain help to handle heavy or hard
manage equipment.manage equipment.
ExperimentationExperimentation
TV Tuner
Amplifiers
Mixer
Frequency Synthesizer
IF filter
AmplifierEnvelope Detector
Non-coherent detector prototype