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When I Think Back... by Neville Williams Hidetsugu Yagi: A pioneer who gave radio antennas a sense of direction Look up the word `Yagi' in almost any book on radio communications, and you will be told that it refers to directional antennas of a particular kind. Rarely do the authors have much to say about the Japanese inventor, whose memory it perpetuates. So who was he, and why does his name now occupy such a conspicuous place in the predominantly 'western' jargon of modern electronics? In my younger days, it took a while in an approved manner, cut to specified UHF bands & equipment to catch up with the idea of designing dimensions and coupled to the transmit- wireless/radio antennas to have specific ter and receiver in a particular way. The 1936 ARRL Handbook also in- properties — beyond, perhaps, the broad In the amateur world, there were cluded special chapters on so-called assumption that big was beautiful! In grounded antennas, Hertz antennas, 'UHF' receivers and transmitters. But the fact, we didn't even talk about antennas. doublets and zeppelins, centre fed, end- designs were still relatively primitive and the associated discussion of UHF anten- In the bush, we put up 'aerials', sig- fed and so on. They were all subject to mathematical nas was, at best, sketchy and concluded nifying 100-odd feet of stranded copper thus: wire suspended by insulators 30 feet or calculation, and exhibited predictable so above ground. There was nothing very directional properties and effective 'A finalftrm suggestion is that a direc- scientific about the design, the physical 'gain'. I was face to face with what the tive array should be used for UHF work- details depending mainly on the space technical fraternity commonly refers to ing wherever possible. Using a directive and resources available to each in- as 'antennas', designed for specific roles. array is an exceedingly inexpensive way dividual set owner. of getting a substantial increase in effec- tive transmitted power'. For sure, we used to argue about in- Logically, one would have expected to sulators of one kind and another, or find reasonable coverage in the hand- which way an aerial should face — but at book of the very practical Yagi-style the end of the day, there seemed little to VHF/UHF directional beams that had choose between them. been developed and documented in Later, when I came to live and work in Japan some 10 years before. Instead, I the suburbs, I found that aerials had been found one lone and non-committal refer- scaled down to a few pathetic yards of ence to them, amounting to less than a insulated bell wire draped from the chim- half-column. ney to an outhouse, or simply tacked to It would seem that, while the ARRL the picture rail around the living room. editorial team was aware of the Dictated by expediency, the chief re- generalities of directional UHF arrays, quirements were ease of erection, and they hadn't got around to much in the their ability to bring in the full comple- way of what we might now visualise as ment of local stations. practical UHF antenna 'plumbing', using Then, around 1936, I experienced the off-the-shelf aluminium rods and tubing. first faint nibbles by the hypothetical In Australia, about this same. time (pre- amateur radio 'bug' — as evidenced 1936) the then-technical editor of EA's from the fact that I bought a copy of the predecessor Wireless Weekly John 1936 ARRL Radio Amateur's Handbook, Moyle, and a number of fellow amateurs which I still have. were spending periodic weekends setting The emphasis in those days was on up 5-metre equipment on mountain out- long distance HF (high frequency) com- crops south and west of Sydney, to iden- munication on the 80, 40 and 20-metre tify accessible vantage points for UHF 'ham' bands and for such a purpose, I Fig.1: We haven't been able to obtain communication. In the process, contacts discovered, aerials could no longer be an original photo of Professor Yagi, had been made over up to about 200km. random lengths of wire — long or short. but this artist's sketch is a good That they were using resonant rod anten- They needed to be erected out of doors likeness. nas goes without saying, but it is unclear 50 ELECTRONICS Australia, October 1991 whether they had made much use, either, Radio, ever on the lookout for an eye- Sydney Morning Herald, owned by our of directional arrays with Yagi-style catching product, making available 360° then parent company. reflectors and directors. glass compass scales for use in back-lit Three years on, a report in what was wall displays of beam direction, when A certain awkwardness then Radio & Hobbies for June 1939 using ex-disposals `Selsyn' motors for But, on the presumption that confes- indicates that by then, 5-metre amateur driving a makeshift antenna rotator. sion is good for the soul, I must admit to activities were on the increase around The Selsyn motors in turn could be a certain diffidence about using the term Sydney and Melbourne, and in Western bought for a proverbial song from firms Yagi' in such discussions. Over the Australia. It mentions that increasing like Ace Radio. years, I had grown accustomed to the use was being made of (unspecified) No less to the point, it didn't take a many 'western' names in electronic jar- directional antennas, mostly vertically genius to calculate a half-wavelength at gon — Ampere, Baird, Boyle, Crookes, polarised. the desired operating frequency and Edison, Faraday, Fleming, Galvani and Again, the August '39 issue of R&H reduce it by about 5% for the driven so on through the alphabet to Volta and carried a report of a `sensational contact' element. Or to work to the original Wheatstone. What was Yagi doing in on five metres between an amateur sta- length for a reflector, or knock off a such auspicious company? With one let- tion in England and another in Italy. further 5% or so for the director(s). ter in the index all to himself? Graphs and tables were also available, The British station was said to be using Could it be that the early tardiness in a four-element horizontal beam, com- postwar, to help determine appropriate element spacing, estimate feedpoint im- taking on board the Yagi research and prising a driven element, a reflector and terminology was a akin to my own two directors. While it would almost cer- pedance and work out how to reconcile it tainly have been a Yagi-based parasitic with the available feed cable. attitude? array, the term still didn't make it into the Whether or not we stopped to think Racist? Undoubtedly! But, since those text. far-off days, I've spent decades trying to rationalise the attitudes originally Wartime technology nurtured in a country school, where we World War II put an abrupt end to such were encouraged to be proud of our activities, but a lot of amateurs (Editor British heritage, of the many red areas John Moyle included) ended up in the in the wall map, and of the invincible armed forces and exposed to antennas British navy that 'rules the waves'; a of all shapes and sizes, among them — school where we made 'big deal' out ironically — Yagi-based arrays. of Wattle Day and a weekly flag After the war, when the affairs of ceremony; an environment where we felt Radio & Hobbies were restored to some openly curious about — and conde- semblance of normality, we found our- Fig.2: Diagram of a Yagi array for the scendingly sorry for — people who were selves beseiged by amateurs keen to get 50MHz amateur band, from the 1948 neither British nor white. How fortunate back on the air. We also found truckloads ARRL Handbook. Construction of the we were to be both, in this great land of beam and provision of a rotatable the free! of =plus VHF and UHF equipment and mounting mast made an interesting miles of high quality coaxial cable. There Years later, it fell to my lot to lead a challenge, rewarded by more and party of EA was a powerful urge to adapt both the stronger signals. readers on a `Technitour' to equipment and the techniques developed Osaka in Japan, via Hong Kong and during the war to post-war amateur com- about it at the time, Yagi's pioneering re- Taiwan, for 'Expo 70'. On that tour, munication. search dating back into the mid-1920's many of us experienced for the first Up-dated information was also avail- had added immensely to the fun of being time what it was like to mingle, as able from post-war textbooks — as, for a postwar amateur, particularly on fre- foreigners, with other races in their example, the diagram in Fig.2 from the quencies from 28MHz up. own environment. I especially remember 1948 edition of the ARRL Handbook, I recall embarking upon such exercises touring around the city of Osaka and showing at a glance the essential dimen- with considerable zeal and subsequently, noticing primary and secondary school- sions for a 4-element 50MHz Yagi beam. along with John Moyle, keeping regular children on class excursions, uniformly The active element depicted is a folded 6-metre `scheds' with amateurs in Can- immaculate in both dress and behaviour. dipole with the two parallel rods/tubes berra and in Young, the latter 270km How very different from my own scruffy, scaled in diameter to provide a suitable away, on the far side of the Great Divid- bare-footed, noisy schooldays! feedpoint for a 300-ohm feedline.

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