After the end of World War 2, the spread of Communism in South East Asia caused the Australian Army to examine its radios. A.W.A. (Amalgamated Wireless Australasia) was asked to design a new portable backpack suitable for jungle use. The specifications required it to be sealed, light, easy to operate, usable on the move, AM, HF, crystal locked on transmit, and use ground wave propagation. A.W.A. set up 3 teams for the project. One team designed the receiver, one designed the transmitter, and one designed the aerials.
SYDNEY TRIALS
Initial work on ground wave propagation for the A510 was done in areas around Sydney, to determine the effects of trees, hills, and buildings. Long wire aerials were measured on the front lawn of the A.W.A. Ashfield factory, and then taken to the rainforest in the Royal National Park to simulate jungle. The aerials were measured over sand, over sea water, and when lying down beside trunks of large trees.
BALCOMBE TRIALS
In January 1952, Lionel Curran and K. G. Dean took the first three laboratory model A510 radio sets, for trials at the Balcombe Army base. The Balcombe Camp was near Mornington, 25 miles from Melbourne.
A base station was set up on Mt. Martha, by Lt. Col. A. W. de Courcy Browne and a VHF set was used in comparison, the type is unknown. Two mobile teams moved down the hill, in opposite directions. At a distance of 100 yards, both the VHF set and A510 could communicate with the base station, but while the A510 could communicate with the other mobile A510, the mobile VHF sets could not communicate with each other. The A510 was still able to communicate at a distance of 1 mile, both to the base station and to each other.
The transmitter Function switch was difficult to use, and a redesign was suggested. It was also suggested that a greater meter reading would be an advantage when tuning the whip aerial.
MALAYAN TRIALS
In April 1952, a party of 5 members went to FARELF Training Centre (Far Eastern Land Forces), Kotta Tingi, 25 miles North of Singapore, on the Malayan mainland. The British Army was engaged in a jungle action against bandit activity in the Malayan peninsula. Australia had committed R.A.A.F. (Royal Australian Air Force) units in 1950 but did not commit ground troops until 1955. The aim of the trials was to test the A510 in tropical jungle, to demonstrate the radio to the British Army, and receive criticism based on their first hand knowledge and requirements, under actual conditions. The civilians were not permitted to leave the base, and conducted their trials from the base, using soldiers in the field. The civilians were also required to wear sidearms at all times.
The party consisted of Lt. Col. D. Small (Department of Supply), Major R. P. Woollard (Directorate of Signals), and Major R. Coutts (Directorate of Infantry), together with K. G. Dean and L. K. Curran as civilian observers representing A.W.A.
The need for maximum aerial efficiency with small radio sets was known and the practice in Malaya was to clear the scrub around the aerial site. For long wire aerials, the simple inclined aerial was not recommended, and a two point supported inverted L type was preferred. The A510 could be used with this type but preferred a dipole.
COMPARISONS
The radio set currently in use in Malaya was the English made WS No.68. This is a 1943 design using octal valves, covering 3-5.2 Mcs. The A.W.A. report states that while the WS No.68 was "probably equal or better than the A510 in power and radiation efficiency, it proved at most times to be inferior in operation to the A510, because of the WS No.68 set's lack of stability, the difficulty in netting it with other sets, and because of the time it took to get it tuned and on the air". The A510 receiver has a sensitivity of 1-3 microvolts compared to 4 microvolts of the WS No.68 set. The A510 has a weight of 16 pounds which is lighter than the 34 pound WS No.68 set. With the A510 mounted on the chest in two pouches, and other gear such as ammunition, weapons, and rations carried on the back, the complete load enabled the man to stand erect. The soldier could still lie on the ground and use his weapon, with the A510 in an operating position, including whip aerial and loading coil. With the WS No.68 set and the standard metal carrier, mounted on the back with the other equipment, the soldier must lean forward to balance the total 70 pounds weight, and sways when walking.
At the time, studies were being done into propagation by D.S.I.R. (Department of Scientific and Industrial Research) in Singapore , and these showed unusual ionospheric conditions in that area, which affected the choice of operating frequencies, these being rather lower than would usually be expected.
The R.E.M.E. (Royal Electrical and Mechanical Engineers) workshops in Singapore were visited to discuss servicing problems in military radios. They noted that failure of the case seal on the WS No.88 (which had a similar type of case to the A510) accounted for only 2% of faults. The majority of failures were due to valves.
TESTS
The base station was FARELF Training Centre, which consisted of cleared or lightly covered land for a quarter of a mile in all directions. The outstation sites were in primary jungle, secondary jungle, rubber plantations, and a 200 foot deep gully. The intervening terrain between base and outstation was rolling hills covered by rubber plantations.
Both long wire and whip aerials were used at the base station to communicate with the outstation. The outstation also used both aerials, and ground wave communication was the preferred propagation method, although it was sometimes difficult to determine whether skywave propagation occurred as well. The speed to which communications could be established under various conditions, were assessed, as well as maximum range. On some tests, there was also a WS No.68 using an 11 foot whip, as well as the A510 using a 7.5 foot whip. The A510 consistently gave better signal strengths.
When using long wire aerials at both ends, the range was 10 miles. Over rolling hills and rubber plantations, when both A510 radios used whips, the range was 3 miles, when the outstation was a whip and the base station a long wire, the range was 5 miles. When the outstation was mounted on a vehicle, (improving the counterpoise), the range increased to 6-8 miles. These tests were done at 3.5 Mcs, as higher frequencies gave less range.
When in primary and secondary jungle, for whip to whip working between two outstations, the range was 1-2 miles, and best using 6-9 Mcs.
The maximum distance achieved was 35 miles, but this was considered unimportant, as both stations used long wire aerials, and it involved skywave propagation.
RESULTS
The A510 trials were considered a success, and attributed to the high sensitivity of the receiver, the simplicity of the transmitter, the general reliability, and stability.
The change made to give a greater meter reading when tuning the whip aerial had been incorporated, as suggested at the Balcombe trials.
There was a recommendation that the viewing of the tuning meter be increased as it proved inadequate when covered with moisture from operator perspiration or heavy rain. The aerial terminal insulation was found to be inadequate for the same reasons, and needed to be larger. There was also a recommendation for a crash limiter due to the noise caused by severe thunderstorms which occurred every afternoon. The function switch was found difficult to use, and a "dummy" redesigned panel was shown, incorporating the ideas from the previous Balcombe trials. The 8 wire earth system for long wire aerials was found cumbersome. The long wire aerial shorting links needed to be improved and a roll up spool developed. Break off tamper-proof case screws were suggested, similar to those used on the WS No.88 radio.
In Malaya, two receivers failed due to humidity affecting the IF transformers. This was due to inadequate sealing of the case to front panel, and the omission of the sealing screws on the IF assemblies. The units tested in Malaya had the pe-production "hand made" cases.
In 1953, Ron Stewart and Lt. Col. Don Small returned to Malaya to test the first production prototypes of the A510.
REFERENCES
Notes on the A510, Personal Recollections, A.W.A. RESEARCH LABORATORY R78-28, K.G.Dean, October 1978.
The Malayan Trials of the WS A510, A.W.A. RESEARCH LABORATORIES REPORT NO. 231, K.G.Dean and L.K.Curran, June 1952.
Emergency and Confrontation: Australian military operations in Malaya and Borneo 1950-1966, Peter Dennis and Jeffrey Grey, St. Leonards, Australia, Allen & Unwin in association with the Australian War Memorial, 1996
Phone conversation with J. Ward, November 2000.
written by Ray Robinson VK2ILV