Dear Sirs,
>From the electromagnetism theory the E field calculated in far field
for a vertical antenna [short vertical monopole] on perfect ground is
given by the following formula:
E = 300 sqrt(ERP)/d
Where:
ERP is the TX power in kW x G gain of the antenna vs the short monopole
d is the observation point in far field in km
E is the farfield in rms values [(mv/m)]
If you would to know how you can reach this formula you have to
consider this equations:
Poynting vector S (ExH) = flux of [ERP] through a sphere with radius d
E^2/120 pi = [ERP]/(4 pi d^2)
For short monopole the gain vs itself is 1 (0 dBSM) so if you use
1 kW = TX power you will find 300 mV/m at 1 Km.
If you use NEC2 you will find the same result (you have to transform
peak values in rms values). Also the gain is correct = 4.8 dBi (3
times the iso gain)
If the ground is not perfect you have to model it and calculate the
field with RP 2 card.
Best regards to all
ALBERTO FASSIO
Received on Mon Oct 06 1997 - 09:23:52 EDT
This archive was generated by hypermail 2.2.0 : Sat Oct 02 2010 - 00:10:38 EDT