Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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]
    From this i am getting E=106.5mV/m
    But the answer is 4.8μV/m
    Please tell where i am wrong...
    Last edited: Dec 2, 2011
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?