History of wireless telegraphy and broadcasting in Australia/Topical/Publications/Australasian Radio World/Issues/1937 12

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Front Cover

The Australasian Radio World

DECEMBER 1, 1937; Vol. 2 - No. 8; Price, 1/-

Registered at the G.P.O., Sydney, for transmission by post as a periodical

Cover Photo: Photo of W.I.A. National Field Day activity (See Page 8)

Highlighted Contents: Amateur Communications Battery Superhet: Making a Reiss Microphone: More about the "De Luxe Fidelity Eight": 15 and 25-Watt P.A. Amplifiers: Latest World Shortwave News.

P.02 - Editorial Notes

Editorial Notes . . .

Nil

P.02 - Contents Banner

The Australasian Radio World

Incorporating the

All-Wave All-World DX News

Managing Editor - A. Earl Read, B.Sc.

Vol. 2. - DECEMBER, 1937 - No. 8.

P.02 - Contents

CONTENTS:

The A.C. "Empire All-Wave Three" . . . . 3

Tasman Crossed On "Five" . . . . 7

Radio Ramblings . . . . 10

Battery Amateur Communications Superhet . . . . 12

A 15-Watt Public Address Amplifier . . . . 15

25 Years In Amateur Radio (8) . . . . 18

Making A Reiss Microphone . . . . 20

15 And 25-Watt Public Address Amplifiers . . . . 22

Radio Step By Step (13) . . . . 25

Assembling And Wiring The De Luxe Fidelity Eight . . . . 26

Round The Shacks (5) . . . . 29

Fiftieth Transmitting Member Joins Lakemba . . . . 30

What's New In Radio . . . . 34

Breaking Into The Amateur Game (11) . . . . 38

All-Wave All-World DX News . . . . 41

Shortwave Review . . . . 42

Shortwave Station Addresses . . . . 44

DX News And Views . . . . 45

VK Amateur Transmitters - Additions And Amendments . . . . 47

Level Indicator For Public Address Systems . . . . 48

P.02 - Publication Notes

The "Australasian Radio World" is published monthly by Trade Publications Proprietary, Ltd. Editorial offices, 214 George Street, Sydney, N.S.W. Telephone BW6577. Cable address: "Repress," Sydney. Advertisers please note that copy should reach office of publication by 14th of month preceding that specified for insertion.

Subscription rates: 1/- per copy, 10/6 per year (12 issues) post free to Australia and New Zealand. Subscribers in New Zealand can remit by Postal Note or Money Order.

Printed by Bridge Printery Pty. Ltd., 214 George Street, Sydney, N.S.W., for the proprietors of the "Australasian Radio World," 214 George St., Sydney (Footnote P.48)

P.18 - 25 Years In Amateur Radio (8)

25 Years In Amateur Radio . . . (8)

In this instalment the author describes how in 1932, in company with a few fellow-VK's he commenced exploring the possibilities of the ultra short waves. Written for the "Radio World" . . . By DON B. KNOCK, Radio Editor, "The Bulletin."

After a period of radio sales and service work, experimental work was carried out with a limited amount of equipment, and using low power, from Bronte, Sydney. This location could be classed as about one of the world's worst. The residence was below road level, being reached by a long flight of steps, and the consequence was that an aerial system, even on 50-foot masts, was only two or three feet above road level.

Despite this severe handicap, a fair amount of excellent communication was obtained on 40 and 20 metres with overseas stations, and some satisfactory 10-metre work was also done with interstate stations. The aerial was efficient, which explained the results. It was a centre-fed 135-foot top running North and South, and despite the heavy screening, reached out very well. The experiences with the station in this undoubtedly poor location brought home the realisation that there can never be a totally impossible location for shortwave communication. It was well demonstrated by reason of the fact that some very useful pioneering work was done on five metres, and for such work one can only comment that the location was well-nigh disheartening.

Early Ultra Shortwave Experiments. At this period, a few of the older hands were turning to five metres for other fields to explore, and among these with the writer were VK2SA (Sgt. Salmon of the N.S.W. police radio service) and Syd. Maguire (VK2XY). These two stations were situated over two ranges of hills in a northerly direction, about three miles distant. With what may now be considered as the most elementary of ultra-shortwave transmitters and receivers, very little trouble was encountered in obtaining good two-way and duplex telephony working.

The transmitters were unstable modulated oscillators, receivers were battery-operated super-regenerators, and the aerials of various kinds, but all plain radiators and not directional. The Pickard type of aerial was favoured at this time, and this is fundamentally about equal to the usual twisted pair doublet.

It was known that over on the other side of Sydney the Lakemba Club had a few members keen on five metres, and engaged in experiments, but Lakemba was then looked upon as excessive DX, and somewhat unlikely as a communication goal from the Eastern suburbs. Nothing was ever heard of the stations over there from the writer's location, but VK2SA, who was more favourably placed, once thought he heard a weak station. In view of subsequent work and achievements in recent years, we can now look pityingly on our former modest hopes!

Back To Radio Journalism. In 1933, the writer returned to the sphere of radio journalism by an appointment as Technical Editor of "Australian Radio News," then published by "The Bulletin," and during the period until this weekly was absorbed in "The Bulletin," a considerable amount of 5-metre investigational work was done. The foundations were laid for an influx of enthusiasm for this previously-scorned communication channel, and more Sydney amateurs were attracted to its possibilities as a very useful cross-city medium.

Following on the initial tests at the home location, with its serious handicaps, possible high elevations were sought with the object of determining just how far signals could travel with the apparatus available. A portable station was made up on a camera tripod. The transmitter had two 71A's in unity-push-pull with two similar valves as modulators in parallel, while the receiver was a separately interrupted super-regenerator with 2-volt battery valves and a magnetic speaker.

This station was taken to the tower on top of "The Bulletin" offices in George Street, Sydney, where a Pickard type aerial was rigged on a wooden support. At once the advantages of an unscreened location became apparent. It was possible to work with the 5-metre gang in all directions around Sydney, as far afield as Mascot aerodrome.

Special duplex tests were run between this station and a police outfit operated by VK2SA from police H.Q. in Philip Street, and a new and interesting era began to dawn in experimental 5-metre radio in N.S.W. Tests were also run about this time in conjunction with Syd. Colville at Mascot aerodrome, and considerable success was had in working over distances up to 20 miles between ground station and 'plane.

Much interest was aroused by the demonstration of 5-metre duplex communication between the "Australian Radio News" and Ever Ready Battery Co.'s stands at the 1934 Radio and Electrical Exhibition in Sydney Town Hall. All this time, transmitters and receivers had been crude, and aerials an inefficient means to an end.

DX With Directional Aerials. With the coming of the directional aerial era on 5 metres in Sydney, this once short-range band began to take on a different aspect. Up in the Blue Mountains, at Hazelbrook, N.S.W., was located a keen experimenter in E. B. Ferguson (VK2BP). Ferguson had dabbled with 5-metre apparatus in the hope of hearing something of the Sydney stations, but after meeting repeatedly with a wall of silence, had more or less given up the quest in disgust.

Late in 1934, a new type of 5-metre aerial was erected at the writer's station (where the previous location had been changed for a more elevated position), this being of the four radiator-four reflector type with the radiators fed in phase, and giving beaming in one direction. It was a bulky affair on a wooden framework, and was perforce so slung between two poles that it gave direction due west.

The transmitter was a T.N.T. oscillator using 45's, modulated in Class B by a 53, driven by a 56. Two keen co-operating experimenters at this time were Harry Chinner (VK2CG) and Will Dukes (VK2WD). It was arranged to run a distance test on this aerial, and on 2 February 35 these two left Sydney by car, carrying a small super-regen. receiver, to make observations on a constant modulated tone signal from VK2NO.

They couldn't lose the signal anywhere along the Mountains Road route, and at Hazelbrook, outside VK2BP's shack, the signal was at maximum. Ferguson was away from home, but a note was left notifying him of the test and the result. To cut a long story short, in a few days' time VK2BP was on the air with a similar beam array, and perfect two-way telephony was established on 5 metres between Sydney and the Blue Mountains.

Active stations using beam arrays following this period were VK's 2BP, 2NO, 2CG, 2WD, 2MW and 2OD. It was attempted to get through to Newcastle, 70 miles airline distance, but that objective was not to be attained until much later, in mid-1937.

Severe QRM Hampers Progress. Several more stations began to be attracted to 5 metres, and the band actually took on a severe QRM aspect. It began to be realised that "squegger" receivers were worse than atrocious in causing severe interference for miles around, and the heavily-modulated self-excited transmitters were guilty of greediness!

Several transmitters were modified by the use of stable grid and plate circuits using the "long lines" principle, and the cleaner signal was at once apparent. Super-regenerative receivers also came in for attention, and separate interrupter valves and an r.f. stage were incorporated in many instances.

It was possible to fit more stations into the band without overlap, but things were by no means perfect. Several misguided people made up simple one-valve transceivers. One of these on the air, with its "squegging" detection and propensity for hopping about all over the band, was sufficient to wreck communication between several stations. It is safe to assume that the "transceiver" as popularised in U.S.A. by several publications did more to hold back progress on five metres than anything. One can imagine the terrific QRM these contraptions must cause in populated districts in the States.

Mobile Tests On "Five." In 1935, a mobile 5-metre test period predominated around Sydney, and several amateurs co-operated in tests far afield. Those test days were full of the most intense interest for those out with the car stations and those at the home locations, and it is a great pity that at the time of writing, this phase of 5-metre activity has suffered from neglect.

The car station for VK2NU (VK2NO's portable) used a unity push-pull oscillator with two 89's, plate-modulated by a 42. The aerial was a half-wave twisted pair doublet projecting vertically from the front bumper. Power was taken from the car 6-volt accumulator via a 300-volt. Carter genemotor, and the receiver had a 955 "acorn" self-interruptor detector and 38 audio.

Many interesting results were obtained with this mobile station, one of which was the fact that a really good place for 5-metre transmission and reception around Sydney is in the centre of the Harbour Bridge. In view of the great mass of steel, this seems hardly likely, but it is so. On one occasion this car station communicated with a similar outfit in a car on Kurrajong Heights, when located near the top of Bulli Pass. These stations were used for lengthy periods when on the move at high speed as well as when "on location."

One important result arising from all this mobile 5-metre work is the establishment of the fact that an undoubtedly ideal location for an ultra-shortwave television station to serve the whole of Sydney and even farther afield is somewhere in the Blue Mountains. With only a 5-watt 5-metre oscillator, it is easy to put a strong signal over Sydney on 5-metres provided that a beam aerial, even in quite simple form, is used at least at one end. A 10 k.w. station working around 6 or 7 metres for television purposes would assuredly cover a wide area with a strong service signal, even from as far afield as Mt. Victoria.

Television for Australian "viewers," however, seems to be a long way distant, for justifiable financial reasons, but no doubt that time will come in the end, and when it does, accumulated ultra-shortwave experience will be of value. My advice to the experimenter with other ideas than DX contests is to get in on the ground floor of ultra-shortwave radio, for it will become increasingly important in the wide future of radio communication generally.

Photo of 2NO and 2XO at Bellingen 1930s

A question of aerial feeder design? The author (left) being shown round by 2XO at Bellingen, N.S.W., a few years ago.