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THE WAY I SEE IT By NEVILLE WILLIAMS Would you please pass the salt? I need a few grains! If there's any truth in the old saying about accepting dubious propositions "with a grain of salt", some of the statements that have been bandied around recently in the context of video and audio are surely calculated to increase considerably one's intake of sodium chloride! First up, there's the dicey business of moving TV channels into the UHF band. In fact, this rather cantankerous heading and introduction was triggered by yet another discourse from TV presenter Bill Collins, on the subject of computer coloured films. The same theme has been repeated so many times in so many places that it's difficult to treat it as seriously as some would apparently wish. But more about that later. Even before I had time to put finger to keyboard, that particular topic was overtaken by an unexpected update from the Illawarra area, along the southern NSW coastline, where broadcasters, service organisations and viewers are currently in the throes of changing over to an all-UHF system of TV broadcasting. (This same area provided the setting for the "Serviceman's Log" in October last and the accompanying map may be of assistance to interstate readers). I discussed the reasons for the changeover in the May issue of SILICON CHIP, under the heading: "Is UHF TV Really as Good as it's Cracked Up to Be?" A follow-up item "The Switch to UHF TV on the 44 SILICON CHIP NSW South Coast" appeared on page 37 of the October issue. Most readers should still have the articles on hand so I will resist the temptation to re-state their contents. In both articles, I expressed misgivings about official attitudes and the possible implications for some viewers currently dependent on the VHF transmissions. Hence the heading on the May article, as above, and the reservation expressed on page 17: "How reception will compare across the total community remains to be seen. I'd be surprised if there weren't plenty of complaints over the first few months". The problems take shape That observation is already looking like an understatement. Since it was written there has been rising apprehension among those who are actually coming to grips with UHF TV in the area, culminating in what have been dismissed by some as "alarmist" statements locally and in the regional press. When brought to my notice, I could think of no better person to contact than Jim Yalden (VK2YGY), a TV serviceman who works in the area. Not only is he actively involved and well informed about the local scene but his practical experience dates back to a lengthy stint in the UK, when UHF colour television was being established there around 1970. Having acknowledged that some of the stories doing the rounds were "alarmist", Jim went on to describe a situation that, itself, seemed to me to be nothing short of alarming for some viewers at least! Since I first discussed the matter with him, earlier in the year, he and his fellow servicemen have been busily installing UHF antennas in the Illawarra area and observing at first hand reception from the three main UHF transmitters on Knight's Hill, near Wollongong, all currently operating at full power. As I write, the antenna(s) have yet to be reinstalled on a somewhat taller mast on the same site but the results so far have been anything but encouraging. The additional height may help but then again, it may not. Recently, an engineer from a major Sydney TV station mentioned to me a situation that he'd come across in a middle east country. Having installed the antenna on a lofty tower dominating the flat desert-like countryside, engineers expected the signals to " go on forever". Instead, the coverage was described as "pathetic". The situation improved dramatically, however, when the antenna was lowered from 300 metres to less than half that figure. Fig.1: this map shows the area affected by the changeover to UHF. Despite high power, shadowing and severe fading are causing problems. The problem was apparently due to atmospheric ducting and while it involved VHF signals in that instance, something similar could conceivably affect UHF transmissions. Limited coverage & fading As matters stand on the NSW South Coast, the UHF signals are proving to be noticeably less accessible in remote or shadowed areas than the existing VHF service and that alone may affect a lot of viewers. No less disturbing is the fact that the UHF signals appear to be subject to periodic fading, presumably due to fluctuating atmospheric conditions over the relatively long signal paths involved. The fading is much more noticeable than was encountered by Jim Yalden in the UK, or by one of his fell ow servicemen in Canada and the USA. Time and again, Jim said, installers have measured · the field strength at a customer's home, before erecting a UHF antenna. When they've returned later with the hardware, they've been faced with a totally different reading. At Jim's own home, about 80km from the Knight's Hill transmitters but otherwise well sited, he receives a relatively good picture, at a signal strength that averages about 800 microvolts. But it swings periodically through a range of about 6dB. For other viewers, in poorer locations or further out, the fading spells the difference between "watchable" signals and periodic complete "blank screen" drop outs! A proposition, accepted in the area, is that planning has proceeded on the broad - but technically dubious - assumption that, given a substantial increase in ERP (effective radiated power), the reach of similarly sited UHF transmitters should roughly approximate that of their VHF counterparts. Accordingly, the new ABC UHF transmitter is rated at 600kW and the commercial WIN-4 at the maximum permissible lO00kW; this compared with the 100kW limit for VHF. But things aren't working out that way in practice because of manifestly different UHF propagation characteristics, the unexpectedly severe fading effects and the fact that comparable field strength is not good enough. At UHF, typical domestic receivers require a larger signal to ensure a clean picture, around 500µ V rather than 200µV. Expecting too much? Jim Yalden expressed the convic- UHF TV - tion that many people have a quite unrealistic impression of overseas UHF TV services. In Britain, for example, the industry tends to regard 30-35km as "deep fringe". At Winchester, he says, about 90km from London, there was no trace of the 1-megawatt London transmitter and no one expected otherwise. Where he was staying, just out of Winchester, a good signal was available from a 500kW transmitter on the Isle of Wight, 25km away. But the house was on the advantaged side of a local hill. Viewers a few hundred metres away on the other side of the hill weren't so fortunate. When visiting a relative in Somerset three years ago, TV reception, according to Jim, was "dreadful" . And there were plenty of other places that were no better; in Wales and parts of Scotland for example. So Britain still faces TV coverage problems, despite something like 70 base transmitters and a host of translators serving the relatively compact country. By contrast, in the NSW 11lawarra area, 30-35km has long been accepted as little more than an average viewing distance for VHF, with the "deep fringe " more like 100km out. That's the sort of expectation that the new UHF service is supposed to live up to, with one base transmitter per channel and a handful of scattered translators. Add to that hassles about the siting of translators and an alleged Questions and Speculation • If UHF coverage, as planned, proves to be inadequate, will the DOTC support the installation of extra translators, as necessary, or will isolated communities be expected to install their own, or rely on transmissions from the satellite? • Some maintain that the mid north coast area will pose even greater problems at UHF than the lllawarra area, by reason of the hilly plateau between the mountains and the sea. Will the DOTC reexamine UHF technical planning for that area, in the light of the emerging situation south of Sydney? • In the ultimate event of a 3-network commercial system covering the whole of Australia, will the participants be obliged to serve isolated communities as well as the larger population centres? • To what extent will viewers Australia-wide, who may be disadvantaged by a changeover from VHF to UHF, be supported by the Government or be obliged to rely on their own resources? DECEMBER1988 45 THEWAYI SEE IT - CTD lack of commitment by the incoming major commercial networks to the fringe areas and the immediate prospect for some remote or isolated pockets of viewers is anything but rosy. Not only may they not receive the incoming networks - if and when they materialise - but they stand to lose one or both of the existing services. Problem areas which have been specifically mentioned range froin deep pockets in the immediate area of the main transmitters, to Kangaroo Valley in the west and to Bateman's Bay in the south. These areas presently get by with a patchwork of VHF signals, direct or via translators. In the face of those and other situations, according to Jim Yalden, there's likely to be "one almighty hell of a scream" on the day they switch off the channel 4 and 5A VHF transmitters - maybe in January or March; who knows? She 'II be right, mate! That's about where we left matters on the morning of September 26, after a couple of phone calls and a round-robin "rag-chew" on the 2-metre amateur band. But on Wednesday the 28th, the MiltonUlladulla Express carried an assurance by the Federal member for Gilmore, John Sharp, to the effect that no viewer in the MiltonUlladulla area would be disadvantaged by the imminent changeover to UHF. It sounded like a political promise of the kind that his constituents most wanted to hear but it was reportedly based on a firm assurance from the Department of Transport and Communications. When asked whether everybody in the south eastern television market would receive improved or at least comparable services next year, their reply was an unqualified "Yes". Said Mr Sharp: "They have assured me that many people will in fact receive improved service and certainly no one will lose what they already have, even if this is only a relatively poor existing signal". While some viewers may have been reassured, I gather that the 11lawarra technical bods reacted otherwise. But unlike the one-time gentry with their snuff boxes, they are passing around pinches of sodium chloride! How could the Department possibly give such an undertaking in view of the limited penetration of UHF signals, the unresolved fading effects, the distances involved and the strictly limited number of translators envisaged? Perhaps even Mr Sharp was reaching for the salt cellar when he added [as quoted): "I will certainly remember this guarantee and it is gratifying the Department has finally been able to provide such an assurance". In the meantime, I did not invent the questions posed in the accompanying panel. I've simply summarised what has been put to me. See what you think. Colourising B& W films From UHF TV I return to the subject of computer-aided colour reprocessing of black and white films mainly intended for presentation on television. Faced recently with the screening of such a film (correction, video tape), TV presenter Bill Collins launched into the usual apologia, acknowledging objections to the process voiced by some film makers and reminding purist viewers that they had the option of turning off the colour and viewing the original monochrome image. How much longer do we have to put up with this tedious preamble at every mention of a computer colourised film? I seriously doubt that many viewers would have followed Bill Collins' suggestion to kill the colour - or that he really expected them to. Because I had other things to do, I didn't watch the feature right through but I did view it for long enough to register whether or not the colour was so patently artificial as to compromise the original image. In fact, from what I saw it was ordinary enough for a non-alerted viewer to accept it as just another colour print. That was certainly the aim back in 1977, when the first-ever computer colourised documentary footage of World War II was intercut with new footage in a mini series on Dwight Eisenhower , featured by the ABC [American Broadcasting Company). Millions of viewers didn't notice the difference between the two, simply assuming - if they thought about it at all that the documentary material had also been shot in colour. For Ralph Weinger and Donald Havens, credited with the early development of the system, it was exactly the reaction they wanted. Despite this, quite a few film makers, actors and purists have condemned the process as akin to sacrilege and sought to raise legal barriers to restrict its use. Sure, serious black and white photography may qualify as an art form, with an arguable right to be respected as such. Some actors may also reasonably object to their person and work being artificially prettied-up and time-shifted out of the era in which they worked. One can't blame the various parties for pursuing whatever rights they may have in the matter - but enough is enough. The fact is that most early films were shot in black and white There's likely to be one almighty hell of a scream on the day they switch off the channel 4 and 5A transmitters maybe in January or Morch; who knows. 46 SILICON CHIP because colour was not a viable option at the time. When they appear on the TV screen today, the lack of colour is a constant reminder of their age - like a travelling subtitle: "This is an old film, to be watched only as a last resort". Many such films may not be suitable for present-day showing, or of sufficient merit to justify expensive reprocessing. But where they are, let's drop the apologetics and enjoy to the best possible advantage the cinematic products of other days. Let's be thankful for modern computer and digital technology which makes it possible to minimise some of the print faults in old "flicks", to reconcile dissimilar frame rates, clean up noisy sound tracks and add credible colour. That way, they might be justifiably rescued from musty vaults or from TV time slots in the wee, small hours. Optical fibre links But enough of television, films and video tape. Here's something for audio types to ponder. That well known hifi buff, Auric Lugg, has discovered that thanks to the near-magic of solid-state integration, opto coupling components for audio systems have become available: small, efficient and (for him) affordable. He looks quizzically at the cable links between the various components of his domestic hifi system. They're good quality cables, every one of them tipped with gold-plated plugs, fitting into gold plated sockets. Inductance, capacitance and resistance are demonstrably much too small to adversely affect the signal. But Auric Lugg's curiosity knows no bounds and he invests in two sets of the new opto couplers, along with two half-metre lengths of suitably terminated optical fibre cable. Following the instructions very carefully and very methodically, he substitutes the new opto coupling devices for the original metallic sockets and cables feeding the main amplifier. This done, he switches on and professes to be absolutely amazed by what he hears. The difference is not of the subtle kind, revealed only by careful A-B testing. It's as if a veil had been lifted from between him and the loudspeakers. The sound, he says, is dramatic, stunning, unbelievably pure! The noise, distortion and unmusical harshness characteristic of wire connections has been totally eliminated by installation of the fibre optic cables, which are claimed to be completely free from such imperfections. I jest? I'm letting my imagination run riot? No! I've simply assembled a word picture from phrases currently being used to promote the provision for optical links . in the latest generation of up-market audio gear. You can swallow it if you like. Me? I'm taking it with a grain of salt. Fibre optics are OK I am not by any means opposed to fibre optics, as such. It stands out as a breakthrough in communications technology. • The National Australia Bank, for example, has installed an optical fibre network in its Melbourne administrative centre to interconnect computer terminals, the communications network and the building control system. • Optical fibre ea ble has been laid around Sydney Airport to link the various radar transmitters with the operations centre. Unlike the coaxial cable which it replaces, it is inert to humidity, corrosion, earth loops, electrical noise and lightning strikes. • Optical fibre cable was chosen in preference to coaxial cable to bring together at the control building the very wideband signals from the 0 six mobile dishes forming the Australia Radio Telescope at Culgoora. • Over the next few years, Australia's internal and external communications will become progressively more dependent on optical fibre cables. • In the October issue, I reasoned that the concept of "fly by wire" should be replaced by "fly by optical fibre" in the quest for greater safety. In short, fibre optic technology offers considerable advantages in terms of economy (especially over long distances), physical durability, exceptionally wide bandwidth, high traffic density and a high degree of immunity from electromagnetic interference, natural or man-made. None of those advantages has any obvious bearing on the transfer of audio signals over the metre-long (or less) paths in a home hifi system. It may be trendy but I fail to see how the substitution of an optical link for a normal, adequate wire link can contribute anything to the subjective quality of the signal. In due course, mass produced optical fibre hardware and connecting cable could conceivably become tidier and easier to handle than shielded copper cable. It may also get designers off the hook by isolating signal paths from considerations to do with equipment earthing (or non-earthing) for safety reasons. In the meantime, optical links may provide a novel sales feature to distinguish the latest models but as an effective way of removing yet another in that seemingly endless sequence of acoustic veils, I'd need to be convinced. ~ ft~ uo/. ,,~ . ~ :..OU rll; uv1 - ~ "CJIIPIIII""~ RCS Radio Pty Ltd is the only company which manufa.ctures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 4-HOUR TURNAROUND SERVICE DECEMBER 1988 47