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<p><b>New page</b></p><div>'''Marconi's law''' is the relation between height of [[Antenna (radio)|antennas]] and maximum signaling distance of [[radio transmission]]s. [[Guglielmo Marconi]] enunciated at one time an [[empirical law]] that, for [[radio transmitter|simple vertical sending]] and [[radio receiver|receiving antennas]] of equal height, the maximum working [[radio telegraphy|telegraphic]] distance varied as the square of the height of the antenna. It has been stated that the rule was tested in experiments made on [[Salisbury Plain]] in 1897, and also by experiments made by Italian [[naval officer]]s on behalf of the [[Royal Italian Navy]] in 1900 and 1901. [[Captain (nautical)|Captain]] [[Quintino Bonomo]] gave a report of these experiments in an official report.{{Citation needed|date=December 2010}}<br />
{{see also|Radio propagation}}<br />
<br />
==Description==<br />
{{expand section|date=December 2010}}<br />
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<br />
If ''H'' is the height of the antenna and ''D'' the maximum signalling distance in [[meters]], then we have, according to ''Marconi's law''<br />
: <math>H = c \sqrt{D}</math>,<br />
where ''c'' is some constant.<br />
<br />
{| class="wikitable"<br />
|+Marconi's law<br />
|'''''c'''''<br />
|'''''D''''' <br />
|'''Apparatus'''<br />
|-<br />
| 0.17–0.19<br />
| {{convert|60|km|mi}} <br />
| Marconi's original apparatus<br />
|-<br />
| 0.15–0.16<br />
|{{convert|60|km|mi}}<br />
| Same, with longer sending spark<br />
|-<br />
| 0.12–0.14<br />
|{{convert|136|km|mi}}<br />
| Marconi's improved apparatus, with jigger<ref>[[Spark transmitter]] [[high-frequency]] [[transformer]]. Marconi's systems used [[longwave]] signals, what at the time would have been called 'high' frequency. The coil [[resonator]] (''coupling transformer'') couples the [[Antenna (radio)|antenna]] [[Electronic circuit|circuit]] to the [[Electronic oscillator|oscillation circuit]].</ref><ref>Fleming, J. A. (1919). The thermionic valve and its developments in radio-telegraphy and telephony. London: Wireless Press</ref> in receiver<br />
|-<br />
| 0.23–0.15<br />
|{{convert|143|km|mi}}<br />
| The same, but with Italian Navy telephonic receiver<br />
|}<br />
<br />
''Marconi's law'' can be deduced theoretically as follows:<ref>Fleming, J. A. (1906).</ref><br />
: Hertz has shown that at large distances compared with their length, the magnetic force of a linear oscillator varies inversely to the distance.<br />
: The maximum value of the current set up in any given receiving antenna varies as its length, also as the magnetic force of the waves incident on it, and as the maximum value of the current in the transmitting antenna.<br />
: Hence, if the magnetic force of the waves incident on a receiving antenna of height and if the distance between the sending and receiving antenna, and if the maximum values of the currents in the sending and receiving antenna, we have various charging voltage of the current in the sending antenna which varies very nearly as its capacity — that is, as its height — and if the sending antenna has the same height as the receiving aerial, we have some constant.<br />
: For any given receiving apparatus a certain constant minimum value of the maximum current in the receiving antenna is necessary to cause a signal.<br />
: Therefore it follows that with given receiving and sending apparatus, we must have a constant.<br />
: That is, the ''maximum signalling distance with given apparatus will vary as the square of the height of the antenna''.<br />
The above law is, however, much interfered with by the nature of the surface over which the propagation takes place.<br />
<br />
==See also==<br />
* [[Georg von Arco|Arco]]-[[Adolf Slaby|Slaby]] ([[Telefunken]])<br />
* [[Electrical lengthening]]<br />
<br />
== References ==<br />
<br />
;General<br />
* [[J. A. Fleming|Fleming, J. A.]] (1906). The principles of electric wave telegraphy. London: Longmans, Green, and Co. Pg [http://books.google.com/books?id=rOAOAAAAYAAJ&pg=PA601 Page 601]+.<br />
* [[J. A. Fleming|Fleming, J. A.]] (1906). Hertzian wave wireless telegraphy. [http://books.google.com/books?id=zRZDAAAAIAAJ&pg=PA42 Pages 42 - 46]<br />
<br />
;Citations<br />
{{Reflist}}<br />
<br />
{{Telecommunications}}<br />
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{{DEFAULTSORT:Marconi's Law}}<br />
[[Category:Guglielmo Marconi]]<br />
[[Category:Empirical laws]]<br />
[[Category:Radio technology]]</div>14.139.155.2