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Aviation History
1949
1949 - 1624.PDF
388- FLIGHT, 22 September 1949 Aircrajt Radio Today . . . only 3 lb. The very small control unit, which has an illumin-ated dial, provides selection for the ten spot frequencies. E. K. Cole, Ltd., are also manufacturing in this field, theirstandard model having eleven channels. Other versions are shortly to be produced which will give up to 21 channels. Afeature of all these sets is that, should a frequency be required that is not already set up in the control unit, the desiredchange can be made during flight by removing the crystals of the unwanted frequency and substituting those of thedesired one. The price of the 11-channel set is approximately /220 and that of the 21-channel, although not finally settled,is expected to be under £300. The 11-channel set is most suitable for small aircraft, being very compact and having apower consumption of only 50 watts. Mention must now be made of what is probably the mostadvanced radio transmitter / receiver yet produced for aircraft, namely, that developed by E. K. Cole, Ltd., for the Ministryof Supply and based on a design of the Royal Aircraft Estab- lishment. This V.H.F. transmitter /receiver provides for nofewer than 312 channels spaced 180 kc/s apart or 281 channels spaced 200 kc/s apart, both these being in the band 100-156Mc/'s. The set is still under Service development and it will be approximately eighteen months before first deliveries takeplace. A multi-channel set which is particularly suitable for usein small or medium aircraft is manufactured by the Plessey Co., Ltd.; it is their type PTR61, which gives a selection ofsix channels. This set may be controlled either at the set itself or at an extension control unit. Provided the operatoris near the set, change of channels by substituting crystals may be made in flight. All these multi-channel sets should make for a great improve-ment in radio service everywhere, for not only do they make things easier and more flexible for the pilots but they alsopermit a much more satisfactory radio organization on the ground. For instance, when the sets are fitted to the majorityof aircraft, it will be possible for each airport to have its own particular approach or airfield-control frequency and thus,where civil airports are situated closely together (as, for example, in the London area) there will be no interferencebetween one control tower and another. H.F. and M'.F. Equipment.—A few new items of equipmentare to be found in this group. Perhaps one of the most interest- ing is the new Marconi high-discrimination aircraft receiverType AD94. This is probably one of the most ambitious receivers made for aircraft use and, apart from the high per-formance of the twelve-valve super-heterodyne circuit, the receiver is fitted with a crystal calibrator which enables theoperator to obtain rapid and accurate tuning throughout the receiver's entire range. The frequency coverage is from 150to 510 kc/s and 2 to 18 Mc/s. To all intents and purposes this receiver is the airborne counterpart of the well knownMarconi high-discrimination ground receiver type RG44 which is now standardized in the Royal Air Force. Another interesting innovation this year is the high-poweredH.F. transmitter, as exemplified in the ST18 developed by Standard Telephones and Cables, Ltd. This transmitter, whichis essentially for large aircraft, has a power output of 140 watts and provision is made for the instant selection of twelvecrystal-controlled channels. The remote-control unit is very compact and enables the pilot to select any one of the twelvechannels, C.W., M.C.W. or R/T. service and high power or low power at the turn of a switch. The low-power switch Marconi H.F./M.F. high - discrimination receiver, AD 108. reduces the output of the set to about 40 watts, a useful featurewhen the high power is not required. These last items should prove valuable in the future if radio telephony is going totake the place of W/T. on the long-distance routes. On the Ministry of Supply stand the new communicationsequipment for airborne use, the ARI5332, was on show. This was developed by Airmec Laboratories, Ltd., to the specifica-tion and basic design of the Royal Aircraft Establishment. It is a high-powered M.F. and H.F. transmitter and receiverfor pan-climatic conditions and high altitude and covers the frequency range of 200 kc/s to 18 Mc/s with remote controlfacilities of up to twelve channels. The equipment is divided into several easily removable units—transmitter, receiver,modulator, etc.—and special attention has been paid to fre- quency stability so that the set conforms to the latest inter-national frequency tolerances. Plessey six-channel PTR 61 equipment, particularly suitable for use in medium- and small-sized air- craft. Remote con- trol is available, and crystals may be changed in the air if the operator is near the set. Multi-channel sets are naturally a little more complicatedbut the general tendency in design has been to make every component easily accessible, a feature which will permit mucheasier servicing and maintenance than on some of the older sets. A full range of aircraft radio equipment was exhibited byboth the Marconi Company and Standard Telephones and Cables, Ltd., whilst specific equipments were seen on the standsof A. C. Cossor, Ferranti, Ultra Electric, McMichael Radio and the General Electric Co., Ltd. Equipments in currentproduction, but not reviewed here, were described in a special article in Flight of April 28th, 1949. GROUND EQUIPMENT There are several items of equipment under this headingwhich were shown for the first time at Farnborough, and they clearly indicate that the manufacturers are fully aware of theneed for improved and more modern equipment in the ground service of civil aviation. Much of the equipment at presentin use was pressed into service directly after the war, for new and better designs were not yet available from the factories.Since that time, however, new radio recommendations and regulations have been made both by I.C.A.O. and by the Inter-national Telecommunications Union, and both these organiza- tions have stipulated rather stricter regulations, particularlyin regard to frequency stability and tolerances. The items exhibited for the first time at Farnborough showed a full under-standing of the latest requirements. Perhaps one of the most noteworthy ranges of new equip-ment comes from Plessey. It is now well known that this company is manufacturing selected items of equipment underlicence from the Bendix Company of America, whose equip-" ment has proved itself both in the United States and in manyother countries. First, there is the transmitter type PT16, which combines a medium-powered V.H.F. and H.F. trans-mitter housed in one attractive 6ft cabinet. This should prove most useful in small out-of-the-way stations where the V.H.F.transmitter may be used for airfield control and the H.F. for point-to-point service. Full remote control is possible up toa distance of 14 miles, and the whole equipment is very thoroughly "tropicalized" to suit the most arduous climatesin any part of the world. As a companion to this dual transmitter there is the single-channel V.H.F. receiver type PR71 and also the single-channel crystal-controlled H.F. receiver type PR51. Both these re-ceivers incorporate the latest circuit technique, including j; 18
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