Sonne (navigation)

Sonne (German for "sun") was a radio navigation system developed in Germany during World War II.

Elektra was an updated version of the beam-based low-frequency radio range (LFR) used in the United States during the 1930s.

Using classical methods, this was normally the measurement of two angles, or bearings, along the line-of-sight to prominent landmarks, like a lighthouse.

As the antenna is rotated around a vertical axis, the strength of the received signal varies, and drops to zero (the null) when the loop is perpendicular to the line to the beacon.

Measurements better than a few degrees are difficult with a small loop antenna, and because of the electrical characteristics, it is not always easy to make a larger version that might provide more accuracy.

Among these was the British Orfordness Beacon which broadcast a signal from a loop that was continually rotating at 1 rpm (6 degrees a second).

Practical development then moved to the United States, where it was used in modified form with two wide figure-8 shaped broadcast patterns that allowed easy capture of the signal.

Ernst Kramar was asked to develop a blind landing system more along the lines of Scheller's original concept.

This emerged as a system generically known as a "Lorenz beam", which used three antennas and phasing techniques to produce highly directional signals only a few degrees wide.

During World War II, even more accurate and long-range versions were used as night bombing aids; see the Battle of the Beams for details.

[7] As the German economy improved and Luft Hansa started a wider schedule, Kramar was asked to develop a system similar to LFF for use in Europe.

Using Lorenz beams, Elektra allowed each signal to be narrower, so a single station could provide a number of incoming and outgoing paths, instead of just four.

In this way a smaller number of stations could be used in order to produce a series of airways that more directly connected airports.

[8] Early in the war the Luftwaffe approached Kramar to see if Elektra could be adapted to allow general navigation, rather than beam-flying.

The keying unit sent the signal briefly to one antenna and then for a longer duration to the second, producing the dot-dash pattern used in the Lorenz systems.

[8] As the antennas were physically separated, the spikes did not precisely overlap, producing the same dots, dashes and equisignal zones of the Lorenz system.

[9] It is a general rule in navigation that the most accurate results are measured when the two bearings are as close to 90 degrees apart as possible.

A total of 18 broadcasters were eventually constructed, some referred to as Sonne and others Elektra, although the reason for this naming is not clear in modern sources.

This proved so useful that Sonne was quickly adopted by RAF Coastal Command, who needed a longer-range system than Gee offered.

Late in the war, when the Germans lost access to Spain, a lack of parts led to one of the Spanish stations going offline.

Compared to systems like VOR or RDF, Consol required nothing more in the navigating vessel than a conventional radio and the ability to count.

The bearing-bearing method of taking a fix using a nautical chart. In this case the navigator has taken three measurements, one against a prominent fuel tank on the shore, and two others against either side of a small island. The use of a third measure allows the position to be more accurately determined, but is not necessary.
White diagram with four rows: first is the letter N followed by a repeating sequence of dash-dot-space; second is the letter A with repeating dot-dash-space; third is A+N followed by a solid line; last line has the word 'time' followed by a right arrow
LFR audio signals: N stream, A stream and combined uniform tone
The Lorenz beam blind-landing system
This portion of a 1946 UK Consol map illustrates the basic concept of the Sonne system. Navigators would determine their rough location using any form of navigation, then tune in the Consol station and start counting the dots or dashes they heard. They would then look up this number on the chart, selecting the line that was closest to their estimated location. The green lines indicate the bearings from the new Bush Mills station in Northern Ireland, red from the Stavanger station in Norway.