a) aparelho usado em radioalinhamento modelo DW-1 com dial azimutal, rotativo, fabricado pela Bendix, Radio em 1941, EUA.
American engineers J. Dillinger, H. Diamond and E. Dumore developed the use of radio signals for the correct positioning of ships and aircrafts in 1930. Basically, The American system consisted of radio beacons transmitting signals
b) indicador de bordo com escala azimutal e a antena rotativa que era fixada na fuselagem da aeronave.
in Morse code, modulated in long waves frequencies. (a) In the beginning of the WWII, the companies Lorenz and Telefunken developed for the German Air Force, LUFTWAFF, a system under the codinome of KNICKENBEIN originally used for guiding aircrafts during bombing missions over England whose radio beacon stations were located in the North Sea coast and in the English Channel.
During the period 1938-1945, numerous positioning-finding systems were developed both in Great Britain and America. They were pulse- modulated system. Amongst them are the Bristish type GEE and DECCA and the American LORAN or Long-range Navigational Aid.
The operation of boths systems is based on determining the difference in the time of arrival at the receiver or radio frequency pulses tranmistted simutaneously or at definite time intervals from a series of
(a) um tipo de radio receptor usado no sistema LORAN.
ground transmitters. The GEE system depends on the use of hyperbolic or lattice charts consisting of a
c) ilustração do indicador de bordo da aeronave mostrando o seu dial ou escala calibrada em 360º.

chain of tranmistters arranged in groups of three or four. Each transmitter operates on the same radio frequencies; usually 20 and 80 MHz. The DECCA system uses low frequency continuous wave-phase, in the order of 100 kHz comparition, to provide continuous position fixing. The American LORAN was based on the same principles as GEE, but operates on a radio frequency of approximately 1900 KHz. (b) The development of the VHF omni-directional radio range, usually known as VOR was developed in 1945. It enables an aircraft to fly along a pre-determined path into an approach zone, and is suitable for furnishing navigational information between the range beacon and aircraft up to 150 to 300 km distant. Unlike the normal course beacons, LORAN provides also an infinite number of tracks radiating from the transmitter. Due to the relative simplicity of its airborne electronic equipment, it could be used as part of the aircraft radiotelephony communication system. (c)

(b) Radio operator on board aircraft using radio system navigation, circa 1939. (News Radio)

(a) Illustration of DECCA radio navegation system showing the coordinates, the points with the radio beacons and the indicating instruments of the radio-signal in the panel of the aircraft.

Radio alignment, an invisible road in the sky
(b) Ilustration of the instrument in the aircraft panel, used in VOR system .
(c) illustration of a primitive instrument for positioning and flight orientation.