Field Strength Calculation for an RF Emitter at Varying Distances

[dnyberg2]

If an RF emitter is allowed to produce a field of 25uV/m @ 300 meters distance, how big will the field be at 3 meters? I'm guessing it's a hundred times stronger (2.5mV/m?) but does the 900 MHz frequency of the carrier come into play?

 

[mfb]

The scaling of the amplitude with distance doesn't depend on the frequency or antenna geometry until you get very close to the antenna.

 

[tech99]

The scaling of the amplitude with distance doesn't depend on the frequency or antenna geometry until you get very close to the antenna.

Also, is it over ground or in free space? If over ground we need to know the antenna heights.