Total posts : 45366
Daniel wrote: “In any case, if it is incorrect when it states in the article that “The transmitted field intensity decreases as the inverse square of the distance”, then I stand corrected. Maybe the article is wrong, I found it when looking for a reference to refresh my memory on the topic via the search string: ARRL signal distance “inverse square.” Perhaps someone should inform them?”
Neil has already posted an answer to your ARRL quote, but I thought I’d do a Google search for something authoritative to support the fact that field strength is related to inverse distance, only (not the inverse square). I was amazed when I got to the Wikipedia entry for RADIO PROPAGATION that stated exactly what that ARRL document did.
So I edited the Wikipedia entry, and taking the cue from you I also sent an email to ARRL about it.
Here’s part of what I wrote on Wikipedia:
Doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.
The far-field magnitudes of the electric and magnetic field components of electromagnetic radiation are equal, and their field strengths are inversely proportional to distance. Doubling the propagation path distance from the transmitter reduces their received field strengths by one-half. The reduction of each of these fields by one-half is the result of the power density reduction to one-quarter, over that doubled path length.
As far as something authoritative, below is the equation to calculate field strength (not power) radiated by a 1/2-wave dipole, taken from REFERENCE DATA FOR RADIO ENGINEERS, 6th edition, page 27-7:
E = SQRT(49.2*P)/ R
where P is radiated power in watts, and R is distance in meters
The “R” term is not squared.