electromagnetic radiation & satellites antenna design pete arvedson california science...
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Electromagnetic Radiation & Satellites
Antenna Design
Pete Arvedson
California Science Conference
October 26, 2013
Hosted by Satellite Educators AssociationLesson plan development supported by a grant from NOAA-CREST West
Session Objectives
Relate wavelength and frequencyConstruct 1/10th scale model waveCalculate antenna lengthApply to 5-element Yagi antenna designBuild 1/10th scale antenna
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Solar radiation reaches Earth surface
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Surface features reflect solar radiation to remote sensors
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Satellite sends radio signal from remote sensors to Earth station
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Wave Properties
crest
trough
wavelength, λ (meters)
amplitude
How many waves pass a point each second
= frequency, ν (1/sec or Hertz)Satellite Educators Association California Science Conference 2013 Antenna Design - 6
Electromagnetic Spectrum
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Wave Properties
c = speed of light = 299,792,458 m/s
-in vacuum ~ 300 x 106 m/s
-in metal = 280.225 x 106 m/s
cλ ν
c = λν
λ = c / ν
ν = c / λ
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POES WEFAX frequency = 137.50 MHz
λ = c / ν
λ =
Wavelength from Frequency
m 2.18 Hz 10 x 137.5
m/s 10 x 3006
6
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Build Wave Model: 1/10 Scale
1/10 scale model wave: λ = 21.8 cm
wavelength: λ = 2.18 m
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Antenna Size – First Look
EMR energy resonates in antenna metal wire producing current
Antenna length should match radio signal wavelength
Wavelength for 137.5MHz = 2.18 m
½ or ¼ wavelength is best! 2.18 / 2 = 1.09 m
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Antenna Size - Actual
Hz 10 x 137.5
m/s 10 x 280.225
frequency
metalin velocity λ
6
6
2.182 m
½ wavelength = 1.019 m
1/10 scale model antenna length = 10.19 cm
Hz 10 x 137.5
m/s 10 x 300
frequency
in vacuumvelocity λ
6
6
2.038 m
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Yagi Antenna
1926 Hidetsugu Yagi & Sintaro UdaTohoku Imperial University, Japan
Driven element; parasitic directors & reflectorHighly directional & wavelength selective
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Brent Stirton, http://ngm.nationalgeographic.comSatellite Educators Association California Science Conference 2013 Antenna Design - 14
Design Your Antenna
3.0 cm8.74 cm
92.0 cm9.20 cm
96.8 cm9.68 cm
10.19 cm
112.1 cm11.21 cm
87.4 cm
4.1 cm
18.3 cm
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Extension
Build scale models other antenna typesCalculate antenna length for 1693 MHzBuild several real antennas & determine
which is best for satellite receptionCompare/Contrast crossed Yagi with QHABuild chicken wire parabolic reflector
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CA Science Standards
Grades 9-12: Physics4. Waves have characteristic properties that do
not depend on the type of wave (a, c, e)
5. Electric and magnetic phenomena are related and have many practical applications (e, f, h)
Grades 9-12: I & E1. Scientific progress is made by asking
meaningful questions and conducting careful investigations (a, d, g)
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Contact Information
Pete Arvedson - [email protected] Check out lesson plans in Satellite Educators Association
(SEA) monthly Newsletter…
http://www.SatEd.org More opportunities to involve students doing research:
SEA’s M.Y. S.P.A.C.E.* Program - an international high school collaborative environmental research program using satellite-based data…
http://www.calstatela.edu/programs/crest/
* (Multinational Youth Studying Practical Applications of Climatic Events)
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