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Aviation History
1926
1926 - 0288.PDF
W rlaisii APRIL 29, 1926 munication with the outside world throughout its entirevoyage through Arctic solitudes. The range of the trans- mitter and receiver will probably be, in regions where inter-ference is not great, anything up to 2,000 miles. On the first stage of the airship's journey to the Pole, from Rome toPulham, Norfolk, regular two-way communication with the Air Ministry, London, was established when the " Norge "was over the south coast of France, and was maintained throughout the remainder of the voyage. Receptionappeared to be only limited by the interference of local stations. A good deal of interference can be eliminated byreceiving on the D.F. loops and putting minimum on the interfering station. In the Arctic, where interference will benegligible, no difficulty at all should be experienced. Of particular interest is the direction-finding system whichwill enable the navigators accurately to determine their position and course despite the fact that the compasses willhave reduced navigational value in the region of the Pole itself, due to the earth's magnetic field effect and the factthat actually at the Pole all direction will be due south. The transmitter is an adaptation of the Marconi 0 • 5 kw.Type U set and is suitable for continuous wave and tonic train signalling. In order to meet the special conditionsobtaining in the airship and to utilise to the best advantage the very limited space available the principal components aremounted on a light teak baseboard. These components com- prise two Type T 250 valves, H.F. choke, reaction condensers,send-receive swith, C.W.-I.C.W. switch, and measuring instruments for indicating aerial current, feed current, high-tension volts, and filament volts. WIRELESS EQUIPMENT OF "NORGE" POLAR AIRSHIP : Diagram showing the arrangement of the wireless Direction-Finder aerial loops, which are mounted diagonally round the envelope of the airship. The aerial tuning inductance and variometer form separateunits and, used in conjunction with the airship's trailing aerial, covers a wave-range of approximately 550 to 1,500metres. On the transmitter six to seven amps, may be obtained in the aerial on the optimum waves and four to fiveon the extremes. The two oscillating valves are connected in parallel, and continuous wave signalling is effected by amanipulating key connected in the grid circuit. For tonic train signalling the grid circuit is interrupted by a smallrotary interrupter. Power for the anode circuits of the transmitting valvesand for charging the filament lighting batteries is derived from a combined H.T. and L.T. direct current generatordeveloping 133 milhamperes at 3,000 volts and 14 amperes at 14 volts. The generator is fitted just astern of the wire-less cabin on a locker and is driven by an air-screw with a right-angled bevel drive, as shown in one of the accompany-ing illustrations. The centre of the propeller is about 5 ft. from the side of the gondola, and the angle at which thepropeller faces the air stream can be varied from inside the cabin by a special lever which may be adjusted and locked tosuit the speed at which the ship is travelling or the rate required by the dynamo. The propeller is of the four-bladedtype and is capable of developing about 3 h.p. For emergency purposes a horizontally-opposed twin cylinderpetrol engine of 2| h.p. is mounted on a lightly constructed tubular steel framework which can be quickly fixed justoutside the gondola. The generator that is driven from the air-screw can be quickly attached to this framework by meansof wing nuts. A switchboard fitted with an automatic cut-out, ammeter,voltmeter and " W/T-Charge " change-over switch enables the low tension batteries to float across the low tension side ofthe generator during transmission or to be charged when the transmitter and receiver are not in use. A special type of fairlead is fitted in the base of the gondolafor the trailing aerial, which is 300 ft. long. This fairhead enables a new aerial and weight to be fitted while the airshipis in flight should it be necessary. An ordinary paxolin aerial winch with an expanding brake is supplied. Special Marconi receiving apparatus is utilised both fordirection finding and for ordinary service reception. As in all aircraft, economy of space and the minimum of weight areessential features and to meet these requirements several of the units are utilised both for direction finding and servicereception purposes. A Marconi short wave two-valve, receiver, with a wave-range of 10-100 metres is carried. This is intended for communication with Point Barrow, where a short wavetransmitter is installed. The aerial for this apparatus is a short length of wire fixed between the wireless cabin andone of the engine gondolas. The receiver operates on the batteries carried for normal working. The direction finder loops shown in the accompanyingdiagram, are fitted diagonally round the outside of the envelope the centre of the loops coinciding with the lead-in to the wire-less cabin. The loops consist of two turns of wire, spaced about 9 in. apart. The loops arc doped to the fabric with linen tape,forming a neat and unobtrusive but very efficient fitting. Inside the cabin 8 terminals are fitted on an ebonite panelto which the ends of the loops are connected. This enables the loops to be put in either parallel or series, as might befound most advantageous on the wave length being received. Reception on the radiogoniometer utilises practically the samecircuits as are used for service reception with the trailing aerial. A radiogoniometer unit and a three-range transformer unitare used in conjunction with a high frequency amplifying detector and a low frequency magnifier. A low frequencynote filter is also provided which can be inserted, when desired, into the circuit between the output terminals of the amplifierand the input terminals of the note magnifier. A local oscil- lation generator is provided to enable bearings to be taken onthe long continuous wave stations. The transformer unit comprises three air-core transformerswith condensers for secondary circuit tuning covering wave ranges of 2,000 to 5,000, 4,000 to 10,000 and 10,000 to 25,000metres. The amplifier is provided with six type V 24, valves, with resistance-transformer coupling for high frequencymagnification and a type QX valve for rectification. The note filter circuit is provided with a single type V 24valve and an oscillating circuit tuned by means of a variable condenser. The low frequency magnifier has two transformercoupled type V 24 valves, which can be switched into circuit according to the conditions of reception. The local oscillation generator utilises one type V 24 valve,which can be switched into circuit for receiving continuous wave signals. A 66-volt dry cell battery is tapped at suitablepoints for supply current to the anode circuits of the receiving valves. The valve filaments are run off the battery used forlighting the filaments of the transmitting valves. For the reception of continuous wave, spark and telephoneservice messages a " plug-in " coil tuner covering a wave- range of 300 to 25,000 metres is connected to the high-frequency amplifier in place of the transformer and radio- goniometer units used for direction finding. The tuner is a coupled circuit instrument and is providedwith reaction coupling to the grid circuit. Eleven " plug-in " coils are provided to cover the full wave-range, any one ofwhich can be inserted in the aerial, grid, or reaction circuit according to the wave-length being received. The service receiver utilises the same aerial as that used forthe transmitter, the aerial being connected either to the receiver or transmitter by means of the Send-Receive switchmounted on the transmitter panel. A narrow table is provided for the operator's writing andfor the manipulating key on the starboard outside wall. Under the left-hand side of the table the transmitterinductance is fitted to the floor. A variometer for fine transmitter wave adjustments is also fitted on the left underthe table. A double-pole change-over switch is fitted in the cabin andthe 12-volt lighting mains for the ship are brought to this as well as the wireless 12-volt supply. This enables the ship'saccumulator and the wireless accumulator to be charged in parallel from the wireless generator, and if the ship's maingives out current can be supplied from the wireless accumu- lator, and vice versa. The accumulators used for the ship'smains and for the Marconi apparatus are of the thin plate high discharge type and non-spillable. 256
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