The 33Mc 'Lorenz' Radio Range System
by Roger Meyer, Macarthur Job, Bob Young & Phil Vabre

The first Radio Range to be established in Australia was an experimental beacon installed and maintained by Amalgamated Wireless (Australasia) Ltd (AWA). The Marconi 4-course beacon was installed south of Mascot at Brighton, NSW, and came into operation in April 1936. Its role was to augment existing Direction Finding (DF) facilities at Melbourne/Essendon and Launceston/Western Junction (est. 1935) and at Darwin (est. 1936). The beacon operated on 298 kHz and the aerial crossed loops were fed with Morse 'A' (.-) and 'N' (-.) signals simultaneously. When the pilot of an aircraft heard a continuous tone of equi-signal A and N tones, he was on course. One of the four 'beams' was focused on Canberra for the Melbourne-Sydney route and another on Newcastle for the Sydney-Brisbane route. A third beam was adjusted on Dubbo for the Broken Hill-Narrandera service and the fourth beam was reserved for the trans-Tasman route.

In March 1935 the Government sent Squadron Leader C.S. Wiggins, Director of Signals of the RAAF, and Mr Roy Badenach, a PMG engineer, to examine radio navigation and communications overseas and to make recommendations as to which system Australia should adopt. In America they found that a chain of MF 4-course Radio Ranges (an American version of that installed at Mascot) was being used. These had the limitation of being a purely aural system (i.e. there was no provision for visual presentation to the pilot of deviation from course) and, operating on MF, they were subject to man-made and atmospheric electrical interference.

As part of his report to the Civil Aviation Branch (CAB), Wiggins recommended that the previously proposed MF Radio Range system should be abandoned in favour of a development of the UHF* 'Blind Landing System' which had been developed by Lorenz in Germany. Click here to read a letter from Wiggins to CCA E.C. Johnston setting out the germ of the idea to adapt the Lorenz system.

The system operated on 30 Mcs (30 MHz) and was later adapted to operate on 33 MHz. It used a 1150 Hz modulated carrier, fed to an antenna. Reflectors on either side of the antenna were keyed, one for a period of 7/8 of a second and the other for 1/8 of a second, giving Morse E (.) and T (-) signals. As a result, two distinctive field patterns were produced in the horizontal plane. Along the axis at right angles to the aerials, the dot and dash field patterns overlapped and the signals merged into a continuous tone to form the beam

click here to see a larger version of this photo Wiggins saw the possibility of adapting the Lorenz system to become an en route navigation aid, having the advantages of both visual and aural outputs, and not being subject to atmospheric effects. The one disadvantage of the UHF beacons was their 'line of sight' range limitation. But this could be overcome by mounting the antennae on an 80ft (25m) mast (see left) and siting beacons at intermediate locations en route, e.g. at Kempsey on the Sydney-Brisbane route and at Nhill on the Melbourne-Adelaide route.

An experimental beacon was installed at Melbourne/Essendon in November 1936 and orders were placed with AWA and Standard Telephones and Cables Ltd (STC) for the supply of 10 additional units. At the same time, AWA began to develop a suitable aircraft receiver as the Lorenz airborne equipment had a range of only 15 km.

The need for the installation of navigation beacons was further underlined following the loss of Stinson VH-UHH on the Lamington Plateau, Qld., in bad weather on 19 February 1937. The Stinson carried no radio and, like the Southern Cloud before it, inadequate meteorological information prior to take off and the inability to communicate with the aircraft in flight contributed to the disaster.

One consequence of the accident was to shortly thereafter make radio communication equipment mandatory on all aircraft operating regular public transport services. The drama (which included finding two survivors nine days later in heroic circumstances) and the attendant publicity concerning the lack of radio communications on Australia's air routes, led to the Government promising that "radio beacons would shortly be installed". This accelerated the CAB's plans to create a network of Aeradio Stations equipped with obsolescent long-wave Bellini-Tosi Direction Finders, and an extra six units were ordered as a stop-gap facility.

The Civil Aviation Board (as it had by then become) had no suitable aircraft for flight testing the Essendon Radio Range equipment prior to commissioning. What was required was a modern aircraft with similar flight characteristics to those then flying on commercial air routes. The Board in late 1936 wanted to purchase a Lockheed 12A, but was told by the Government that it must 'buy British'. The only British aircraft available at that time were wood and fabric aeroplanes with no engine-driven generators and very limited night and instrument flying equipment, totally unsuitable for the Board's requirement.

Prolonged negotiations followed between Treasury and, first, Associated Airlines and later Guinea Airways for the hire of a Lockheed aircraft. However, the hourly rate offered was not acceptable to the operators and the prolonged negotiations amounted to nothing. In the meantime, an order was placed for a Percival Q.6, a twin-engined, retractable undercarriage aircraft from the UK but this machine was not delivered until early 1939 (as VH-ABY).

By Feburary 1938 the experimental beacon at Essendon was being tested - but unofficially with a Lorenz UHF airborne receiver fitted to the CAB's Gipsy Moth VH-ULP! The beam-forming technology available in the Lorenz system limited the amount that the reciprocal courses could be 'bent' to about 30 degrees. Photographic evidence indicates that the Essendon beacon was at different times configured with the courses aligned to Adelaide/Flinders Island, and Sydney/King Island.

By the middle of 1938 AWA had prototype Radio Range receivers installed in ANA's DC2 VH-UYB Pengana and Ansett's Lockheed VH-UZP Ansalanta, while Airlines of Australia had a Lorenz unit in their DC3 VH-UZJ Kyilla. Naturally pilots could not use the system for navigation, only for crew familiarisation, but the reports of the pilots were most encouraging and seemed to confirm Wiggins' confidence that a 'blind landing' system could be successfully used as an en route navigation aid.

Unfortunately on 25 October 1938, whilst all the prevarication over the hire of a suitable aircraft for testing the Radio Range was still going on, the ANA DC2 VH-UYC Kyeema, on a flight from Adelaide to Melbourne, overshot Essendon in cloud due to a navigation error and crashed fatally into Mt Dandenong, to the east of Melbourne. It was immediately evident that if the crew had been able to use the Radio Range this accident would most likely not have occurred. Almost immediately thereafter the financial disputes over the hire of Guinea Airways' Lockheed were finalised and Lockheed 10A VH-AAU was flown to Essendon on 2 November to have equipment fitted for flight testing the Lorenz beacons.


click here to read more about Lockheed VH-AAU Tests on the Essendon, Nhill and Canberra beacons began in November, and by September 1939 there were Radio Ranges operating at all points called for under the original inter-capital air routes scheme. They operated on 33.3 or 33.8 MHz.

Stations were commissioned at Adelaide/Parafield, Brisbane/Archerfield, Canberra, Holbrook, Hobart/Cambridge, Kempsey, Launceston/Western Junction, Nhill, Melbourne/Essendon and Sydney/Mascot. Some beacons, such as that at Seymour, were improvised later on.

Marker Beacons were installed at airports where the Radio Range was used as an approach aid. They were located close to the Range and the 1700 Hz tone which they transmitted enabled the pilot to fix his position over the field. A smaller number of 'Approach' markers were provided at major airports. These transmitted an interrupted 700 Hz tone and, when flown over, indicated distance from the runway. Both types of Marker operated on 38.0 MHz.

The Lorenz Radio Range served its purpose well and nineteen beacons were operational it its peak in the early 1950s - the first operational VHF Radio Range network in the world. However, by the post-war years interference between beacons due to atmospheric effects, even from across the country, drove the search for a replacement. The 33 MHz Radio Ranges were finally removed from service in April 1953 with the commissioning of the 112 MHz Visual Aural Range (VAR) network.


* The modern day frequency band allocation would describe the Lorenz system as a VHF beacon.

Click here to read more about the story of radio navigation aids in Australia

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