Electromagnetic Radiation & Satellites

Antenna Design

Pete ArvedsonCalifornia Science ConferenceOctober 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 cm 8.74 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 & E

1. Scientific progress is made by asking meaningful questions and conducting careful investigations (a, d, g)

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Contact Information

Pete Arvedson - arvedson@aol.com 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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