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Aviation History
1962
1962 - 0442.PDF
442 FLIGHT International, 22 March 1962 The tycoon's radio set-up: in a Queen Air, two 360-channel VHF, two 190-channel receivers with VOR/Loc, ADF, HF, weather radar, gyro-magnetic compass and RAW—and full autopilot RADIO: why and wherefore A BRIEFING FOR THE PRIVATE PILOT By Mark Lambert RADIO in aircraft is like smoking cigarettes—expensive, strongly habit-forming and liable occasionally to lead to trouble. But radio really performs a more valuable service than cigarettes and has a resale value: cigarettes on the other hand, are virtually 100 per cent reliable regardless of quality and require no maintenance. From which considerations it can be seen that radio is not just "buy black boxes and follow the left/right needle." The customer considering radio should aim first of all at good-quality equipment in a competent installation. Then he should aim at the widest possible capability, and by this we mean it is worth spending that precious £100 more to get full communications coverage, or navigation as well as communications. Every bit counts and can be worth its weight in gold. It can revolutionize the utilization and usefulness of your aircraft. Imagine, in the words of the gangster novel, a smooth black executive sedan gliding into the London Control Zone, using the call-sign "Cigar"—this means it has everything, including two engines. The tycoon pilot, his eyes mere slits in the soft red glow of indirect instrument lighting, playing his slim fingers deftly over the many glowing knobs and switches. He has every communica tions frequency in the book twice over. No 1 VHF com is being fed into his super-quality head-set (with boom microphone) and the London approach controller is saying "Cigar Whisky Tango, we expect no delay in approach, Sir, you will have radar vectoring onto the ILS for 28 Right." No 2 VHF com is piped into sonny Jim's headphones and he's listening to a Vulcan being talked down at Waddington. No 1 ADF is tuned to a promenade concert and being fed through the hi-fi loudspeaker to Madam in the rear seats. The trailing aerial of the HF radio is reeled out just the right amount to catch continuous advance weather broadcasts from the Azores. The radar transponder is painting the tycoon's per sonal monogram on the tube-face of every radar in the country. The restless trace on the weather radar screen next to the tycoon's elbow in the cockpit, is even now painting the winding Thames and the Staines reservoirs. Our tycoon is navigating with uncanny accuracy, tracking the Decca pen monotonously along the centre of a thin track line on the chart specially printed for him at 24hr notice. Two VOR cross-pointers are displaying bearings, and one of them will soon be retuned to London ILS. No 2 ADF is switched off. Tycoon knows very well that its additional small load would finally overwhelm the electrics and the whole lot would go up in smoke. He also knows that he is returning home for an annual radio overhaul that will cost at least £1,000. That glass to replace cardboard in the windows at home will have to wait. Radio, like keeping up with the Joneses, can get out of hand. Now we might as well start at the beginning and try to set out in simple words what radio is about; and we are here concerned with aircraft of under 5,0001b gross weight, although much of the equipment referred to may be, and often is, fitted in much larger aircraft and airliners as well. This is perhaps the first point to make. The smallest aircraft, provided it has an electrical system, can carry the best radio available. Size is barely important any longer, except in the high-performance, very-high quality airline and military equipment, which is hardly ever necessary for the small aircraft. The customer should regard himself as having a free hand to choose what facilities he wants. A word about frequencies. Very high frequencies (VHF) are measured in Megacycles/sec (Mc/s) and the civil communications band reaches from 118.0/Mcs to 136.0Mc/s. The military goes beyond this and spreads all over the place. Some radios operate on channels which are at odd tenths: 118.1, 118.3, 118.5, at 200kc/s spacing. It is common nowadays for the even tenths to be used as well and even for the half-tenths to be provided, thus, 118.0,118.05,118.10,118.15, etc. The result, obviously, is to provide for more and more frequencies, which makes everyone happy. All the frequencies are of course controlled by pairs of crystals and selected by switching, rather than by sweeping a needle along a tuning scale as one does with a domestic radio. The communica tions band has been sub-divided into lower and upper portions, that is from 118.0 to 126.9Mc/s and from 127.0 to 136.0Mc/s. A radio which covers the lower band at lOOkc/s spacing therefore has 90 channels. The ten Megacycles below 118.0 are reserved for VOR beacons and ILS localizers, five Megacycles each—of which more later— and it is customary for VHF radio which pretends to give full coverage to provide a transmitter from 118.0 to 126.9Mc/s and receiver from 108.0 to 126.9Mc/s. One therefore loosely talks about a 90-channel VHF radio, though it is strictly 190/90 channel. A very useful frequency in Europe is 117.9, the NATO, RAF and USAF "common" channel, which gives access to virtually every military airfield and facility. Many American radio manufacturers have produced "European" versions of their radio to include 117.9 in the transmitter band. On a rather lower level of elaboration there are numbers of radios which cover only a certain number of communications frequencies, four, five, ten, 20, 44, according to their capacity for crystals. In these cases it is up to the customer to choose which crystals he will fit—and to hope that these will cover his needs. In some radios, the crystals can be changed in flight, so that the frequencies available
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