To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
Languages
Recent
Show all languages
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

# Dipole field strength in free space

## From Wikipedia, the free encyclopedia

Dipole field strength in free space, in telecommunications, is the electric field strength caused by a half wave dipole under ideal conditions. The actual field strength in terrestrial environments is calculated by empirical formulas based on this field strength.

## Power density

Let N be the effective power radiated from an isotropic antenna and p be the power density at a distance d from this source[1]

${\displaystyle {\mbox{p}}={\frac {N}{4\cdot \pi \cdot d^{2}}}}$

Power density is also defined in terms of electrical field strength;

Let E be the electrical field and Z be the impedance of the free space

${\displaystyle {\mbox{p}}={\frac {E^{2}}{Z}}}$

The following relation is obtained by equating the two,

${\displaystyle {\frac {N}{4\cdot \pi \cdot d^{2}}}={\frac {E^{2}}{Z}}}$

or by rearranging the terms

${\displaystyle {\mbox{E}}={\frac {{\sqrt {N}}\cdot {\sqrt {Z}}}{2\cdot {\sqrt {\pi }}\cdot d}}}$

## Numerical values

Impedance of free space is roughly ${\displaystyle 120\cdot \pi }$

Since a half wave dipole is used, its gain over an isotropic antenna (${\displaystyle {\mbox{2.15 dBi}}=1.64}$ ) should also be taken into consideration,

${\displaystyle {\mbox{E}}={\frac {{\sqrt {1.64\cdot N}}\cdot {\sqrt {120\cdot \pi }}}{2\cdot {\sqrt {\pi }}\cdot d}}\approx 7\cdot {\frac {\sqrt {N}}{d}}}$

In this equation SI units are used.

Expressing the same equation in:

kW instead of W in power,
km instead of m in distance and
mV/m instead of V/m in electric field

is equivalent to multiplying the expression on the right by ${\displaystyle {\sqrt {1000}}}$.[2] In this case,

${\displaystyle {\mbox{E}}\approx 222\cdot {\frac {\sqrt {N}}{d}}}$

## References

1. ^ Reference data for radio Engineers, Howard W.Sams co,Indianapolis, 1956, 27-7
2. ^ K.H.Kaltbeitzer: Site selection, EBU Techhnical Monograph 3104,Bruxelles,1965, p 30
This page was last edited on 15 March 2021, at 10:55
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.