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The calculation for working out field intensity is as follows:- Field Strength E = (1/r) * SQRT(n G P/4 pi) ,where r = distance, n = 377 ohm, G = gain of the Tx antenna P = RF power fed to the antenna (= Tx output power - cable losses), pi = 3.1415 (The 4*pi comes from the surface area of a sphere being 4*pi*r^2.)
After solving for P, we get
P = ( 2 pi E2 r2 ) / ( n G )
If given E = 35 uV/m r = 3 m G = 0 dBi = 1
=> P = ( 2 * 3.1415 * (35e-6)2 * 32 ) / ( 377 * 1 ) = 0.184 nW = -67.4 dBm While the minimum output power of 3ASd is 10 mW (= 10 dBm), This means that you should install an attenuator of 77.4 dB between the radio modem and the antenna. As a result, only one way communication would be possible because Rx port should not have any additional attenuation. Or for two-way communication, the output power of 3ASd has to be decreased internally.
Estimating the max. communication distances at 180 pW Tx power by a simulator, we get in free space only around 4 m.
If a 10 dBi gain antenna is used at the Rx side, the distance will be around 11 m.
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