# Electric field of antenna

1. Dec 2, 2011

### erece

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