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  The Radio Range

Communications and Aircraft Navigation

by Jack Chalmers and John Gilbert

 

Control of civil aviation operations in Canada was taken over in1936 by the Civil Aviation Branch of the newly created Department of Transport. A Radio Division, headed by Walter A. Rush, Controller of Radio was created within the Branch to develop radio navigational aids to serve the emerging needs of aviation across Canada[1].

 

The future of aviation in Canada at the time was synonymous with the plans of Trans-Canada Airlines. Speaking before The Empire Club of Canada on 27 October 1938 Philip Johnson, Vice-President, TCA recalled that the Trans-Canada Act had been enacted in April of 1937, but as late as July of that year the company existed purely as a corporate entity under a Board of Directors. To define Trans-Canada’s operational requirements an aerial survey was carried out over the route to be flown: from Vancouver, over the Rockies, East to Toronto and Montreal, then to the Maritimes terminating in Moncton. The survey would determine what airway facilities were available. It would propose plans for a radio communication system across Canada and would select the sites for the location of radio navigation stations. Trans-Canada would require fully usable fields, lighted for night flying, equipped with radio ranges, and other facilities necessary for safe navigation of aircraft under the existing techniques of flying.

 

Three parties played a crucial part in meeting Trans-Canada’s mandate for putting in place a transcontinental air line across Canada. First, the Company, charged with the operation and the organization of the actual flying. Second, the Government, represented by the Post Office Department and the Department of Transport. The Post Office furnished a major part of Trans-Canada’s payload, and the Department of Transport the ground facilities necessary to carry out the work. The third partner was the public – soon to discover the delights of flying.

 

Trans-Canada’s planes were equipped for radio reception. The pilot would navigate by following the "beam", a signal sent out from the Department of Transport radio range stations to be installed at about one hundred mile intervals across Canada. When on course the pilot heard a monotone but the minute he got off course he received an "A" signal or an "N" signal in Morse code.

 

The challenge for the Radio Division was to secure the funding (during the Depression), purchase the equipment and build the stations in some of the most inhospitable places in Canada. Initially, in 1936-37, seven old-type radio range stations were taken over from the Department of National Defence. These were partly remodelled until modern stations could be built at more suitable places. The first thirteen stations, completed in 1937-38, were, with the exception of St. Hubert, Quebec, all west of Winnipeg. Work began in that fiscal year on stations east of Winnipeg, many in places, such as Pagwa, Ontario which were remote and difficult to reach. Some of the locations, such as Porquis Junction, Ontario, had no local accommodation for the radio range staff. To meet this need sixteen dwellings, as well as a staff house at Carmi, BC, were built. Many technical problems had to be overcome. For example east of Winnipeg the resistance of conductivity to the ground was said to be about three times as great in the west as in the east. This cut down the effective range of the signal in the latter case and technical means had to be found to overcome the problem.

 

Despite the depression the Government undertook an aggressive program building airports and installing aids to navigation. By 1937 there were sufficient facilities for Trans-Canada Airlines, as Canada's "chosen instrument" in the field of aviation, to begin operating an intercity airmail and passenger service. By 1940, with the extension of passenger service to Moncton, Canada had a transcontinental day and night, all weather, mail and passenger service connecting its principal cities. The radio ranges, provided by the Department of Transport, were the principal aid to air navigation. The war years brought additional urgency to the establishment of radio ranges. A new circuit, started late in 1941, running from Edmonton to Alaska in conjunction with the construction of the Alaska Highway, was known as the Northwest Staging Route[2]. Radio Ranges were also used in support of the “Crimson Route” to England via Greenland and Iceland.

 

By the end of WWII Canada held fourth place world-wide in aviation yielding only to the USA, Britain and the USSR. Most Radio Ranges were, by this time, enhanced with two additional features: station location markers which sent an inverted cone straight from the ground which indicated to the pilot, by means of a light on the instrument panel, when the plane was directly above the range; and ranges were equipped to communicate directly with aircraft via radiotelephone. By the mid 50s there were some 94 radio ranges across the country.

 

While there was some variation in the equipment installed at each station, the basic Low Frequency Radio Range operated in the 200-400KHz band and had four 125-foot towers, set in a square. Diagonally opposite towers were fed with out-of-phase energy in what was known as the Adcock configuration. This produced a figure 8 pattern for each pair. The figure 8s overlapped and had four lobes. The "On Course" signal formed where two lobes overlapped. Each range was keyed in Morse code with its unique identifying letters.

 

Transmitters and gonio at Fort Nelson Radio Range 1944.

Photo: Jack Chalmers

 

A typical range[3] consisted of two 400 watt Marconi or Radio Receptor transmitters (if one failed the other came on automatically) a gonio unit and a control unit. The four steel 125-foot towers were fed from the transmitters through the gonio unit which produced the four courses. These courses were flyable to a distance of approximately 100 miles under normal conditions. A 10 watt cone of silence transmitter, operating at 75 MHz, informed the pilot when he was directly over the station. Each station was equipped with a power unit - a gasoline powered engine driving a 110 volt generator. A service road had to be built and maintained to access the communication transmitters which were located at a nearby transmitter site. 

 

Radio Range Building and Towers. Fort Nelson 1944.

Photo: Jack Chalmers

 

Each of the radio range stations had a staff complement of radio operators. Radio schools across the country provided operator training and many experienced operators from Marine Services, the military and provincial services were attracted to the new service. Radio operators maintained a 24-hour vigil by monitoring all aids and notified the proper authorities when something went out of tolerance. The Radio Operator had a number of duties. Taking, and broadcasting, the hourly weather observations; taking pilot balloon or "pibal" observations (measuring wind direction and velocity using a gas-filled ballon tracked with a theodolite); checking the electrical generator; monitoring the signals of adjacent stations hourly, as well as his own radio range 24 hours a day.

 

Fort Nelson Radio Range 1944. Jack Chalmers, Officer in Charge, in his office.

Photo: Jack Chalmers

 

Operating positions. Fort Nelson radio range 1944

Photo: Jack Chalmers

 

Voice transmissions were used for weather broadcasts and communications with aircraft. At the basic four tower ranges the navigational signal was interrupted when voice transmissions were made. This problem was overcome at major airports by the addition of a fifth tower used to radiate voice transmissions while not interrupting the navigational signal. These stations were known as "Simultaneous Radio Ranges". All range stations also maintained a continuous watch on two standard HF frequencies for two-way communications with aircraft.            Each site was calibrated when established so that one "on course" leg would fall over the major runway at the associated airport and two opposite legs would point to the adjacent airports on the airway. Courses could be adjusted, or bent, by splitting and phasing of the antenna current through a "Goniometer" that adjusted the energy fed to each pair of towers. Flight checking, which often took many hours of flying time, confirmed the accuracy of the radio range courses. Initial calibration of the radio ranges was carried out by Department of Transport Lockheed 12A, CF-CCT which had achieved national attention by its record breaking flight from Montreal to Vancouver on July 30, 1937. The aircraft ended up in the National Aviation Museum.

 

By the 1950s, the Radio Ranges began to fall victim to the development of new VHF Navigational Aids and advances in airborne navigational instruments. Their place was taken by the Very High Frequency Omni Range (VOR) and Distance Measuring Equipment (DME). The distance of the aircraft from the DME could be read directly on the aircraft instrument panel. The ranges were gradually phased out or converted to non-directional radio beacons.

 

The last operational range in Canada was the Castlegar or Crescent Valley Radio Range in B.C. It had been commissioned in 1938 and was shut down in May 1981. For the last few months of its life it only radiated if requested by a pilot. People flew in from all over the Canada and the USA for a last chance to fly the range. The Castlegar equipment is now housed in the Canada Science and Technology Museum in Ottawa.[4]

[1] The major source of information for this article is the Annual Reports of the Radio Division, Department of Transport. LAC Amicus 9588262. The first annual report covered the years 1936-37.

[2] Radio Waves Across Canada and up the Alaska Highway, Lethbridge, 1992

[3] Technical information provided by Ernie Brown and Frank Ryan

 

[4] Sources: Steve Cochran, Bill Newton (email 25 Aug 2005), TC Express, No. 38, May 1981.

 

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