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Homework Help: Electric field of antenna

  1. Dec 2, 2011 #1
    The current at the base of an earthed antenna 30 metres high is 20 amperes at a frequency of 1MHz. Calculate the field strength at a distance of 10 Km.


    Now in this question do we have to consider that field generated from the antenna and field at the distance 10 Km are same ??

    I solved like this....
    power generated from monopole ( as given in question that antenna is earthed)
    P = 80[∏xI]^{2}[l/λ]^{2}
    where l = 2h
    and h=30 m
    l=60 m
    I=20 A
    λ=c/f = 300 m
    So P=37.86KW
    Power density at a distance of 10 Km =P/(4∏[10000]^{2}
    = 30.14uW/[m][/2]
    =[E]^{2}/120∏
    From this i am getting E=106.5mV/m
    But the answer is 4.8μV/m
    I THINK I AM TOTALLY WRONG..........
    Please tell where i am wrong...
     
    Last edited: Dec 2, 2011
  2. jcsd
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