Five miles east of Atherton and about midway between Yungaburra and Malanda, the road crosses Gwynne Creek. Close by, on a 60 acre low lying block of ground described as sub 1 of portion 306, parish of East Barron, country Nares, lies 4AT.
4AT is an unusual national station, as it began life as a commercial owned by Atherton Tablelands Broadcasters Pty Ltd in 1938.
Early in the second world war the Commonwealth Government acquired the station from its owners for reasons believed to concern national security at the time. The date of takeover is uncertain, most likely late 1940. Earliest surviving correspondence dates from early 1941.
The land was leased from Beattie Bros., but the Government paid compensation to the commercial company for the station building and equipment. In the Commonwealth Government Gazette No. 211 of 1 November 1945 it was announced that the land had been bought also. Arrangements were made to enable D. E. Beattie to operate a grazing lease on the property for his cattle and to continue to cultivate part of it which did not affect the aerial earth system.
A site plan was drawn up dated June 1941 which revealed that the station occupied half a house with office, studio and equipment room. The wooden studio floor was double with a sandwich of 4 inches of sawdust, to improve sound insulation. A 500 Watt AWA transmitter type J4825 serial No. 1 was installed, feeding a 365 feet high steel pipe aerial via a two wire 600 Ohm impedance transmission line. A conventional earth mat of 121 wires each 796 feet long was buried in the paddock which was grassed with clover and paspalum for the benefit of Mr Beattie’s cows.
The transition from balanced feeder to unbalanced aerial was achieved with an RF transformer comprising two flat spiral coils separated by a Faraday screen of parallel vertical wires.
The transmitter valve complement was oscillator 42, oscillator amplifier 807, RF amplifier 807, buffer 805, modulated amplifier four 805 in parallel push pull. Monitor diode was an 84. EHT volts 1250 from six 866A mercury vapour rectifiers. The audio was push pull throughout. 1st audio 6A6; second audio two 6A6 parallel push pull; sub mod four 2A3 parallel push pull and modulation four 805 in parallel push pull. Anode modulation of the mod. amp. was used.
The operating frequency was 680 kc/s.
Aerial efficiency and station service area were not measured until 1952. Queensland Engineering Reports QB47 and QB48 by George Barr and Doug Sanderson of the Radio Laboratory were issued to record this data. The figure of merit of the aerial was 180 millivolts per metre for 1 kW at 1 mile, a reasonable value for this quarter wave radiator.
Just prior to this the whole aerial system had been overhauled and repainted by private contractor. New obstruction light fittings were necessary as rusting was severe. During the war years the mast lights had not been used at night unless specifically requested.
QSL card from 4AT for reception on 680 kHz in New Zealand during 1952. © Radio Heritage Foundation, Laurie Boyer Collection.
In January 1954 the station frequency was changed from 680 kc/s to 600 kc/s by Vince Griffin and Ralph Bongers.
When taken over, the station had no emergency engine generator, but in early 1944 a shed behind the house became the laundry and engine room. A Ford V8 petrol engine driving a 10 kVA, 3 phase, 415 Volt alternator made by D. F. Skelley of Melbourne was installed. It had arrived at the Yungaburra railway yard in an open wagon and had been wet by rain on the way. No permanent harm was caused by the water however. Three years later a Braybon automatic voltage regulator was obtained to improve the performance of the emergency supply.
The first permanent OIC was Alf Walker who was at 4AT from 1941 to 1945. Bill Mellish and Doug Macaulay had been on site initially.
Over the years improvements were made to the audio facilities, test equipment was provided and emergency record playing facilities were upgraded. This latter equipment was found most necessary when the station was off program line during the cyclone of 1956.
A report of this cyclone by the OIC makes interesting reading:
EFFECT OF CYCLONE AT 4AT
Programme line: The programme line was broken south of Townsville on 5 March 1956 at 7.57 p.m. No further programme was received via land line until 3.25 p.m. on 10 March 1956 when a telephone channel was supplied. A broadcast channel was provided at 6.30 p.m. the same day. Whilst the programme line was cut, programme was maintained by rebroadcasting radio pickup of short-wave stations transmitting the correct programme. When reception conditions were unfavourable, records were played locally.
Commercial Power: High winds caused many faults on the high tension power lines on the Tableland on 6 March 1956. Our emergency power plant was in use from 7.20 a.m. to 12.53 p.m. this day. Commercial power was available at 4AT throughout the remainder of the cyclone period. The alternator of the emergency plant was not giving full output voltage whilst it was in use but this did not affect 4AT transmission. The alternator output voltage was 370 Volts instead of the normal 415 Volts.
4AT Radiator: As the velocity of the wind rose, 4AT radiator was seen to be flexing. On the morning of 6 March 1956 for instance, I estimated the top of the mast was being displaced 8 feet or more from its normal position. Our nearest neighbour, Mr D. E. Beattie, rang me on 7 March 1956 to advise me that the top of the mast was flexing greatly. After the wind subsided it was found that the mast had retained a permanent set below the cross-trees. 4AT transmission was unaffected by this condition.
Damage to Installations: No major damage was done to the buildings or other aerials in the grounds. Minor damage was done to ornamental structures and trees.
Emergency Short-Wave Communication: On 8 March 1956 we were called upon to provide a morse circuit from Atherton telegraph office to work via short-wave transmission to Brisbane. Telegrams were transmitted and received on 8 and 9 March 1956. Also 8 March 1956, radio contact was made with Cairns Flying Ambulance and Wairuna homestead in the Mount Fox district as fears were held for the safety of people at that homestead and adjoining properties.
Overtime: A total of 17 and one quarter hours was incurred by 4AT staff as a direct result of the cyclone. This was used in manning the short-wave communicating equipment, attending the emergency power plant, and clearing broken tree branches from the guys of one of the small masts.
(K. W. Bytheway)
Supervising Technician 4AT,
Staff movements occurred from time to time. Alf Walker left in 1945 and Gordon Andrews came for a year. Eric Gough was OIC from 1947 to 1949 and was followed by Ken Bytheway who stayed from 1949 to 1956. Jack Barden was in charge from 1956 to 1965, then Ernie Long spent two years in residence. The last O.I.C. was Errol Black, from 1968 to 1973, after which the station became unattended and was maintained by Radiocom staff from Cairns.
During the 50’s, the PMG emergency radio network was extended to 4AT. A Temco 200 Watt HF transmitter was provided, with two AR7 receivers. This gave emergency voice contact with Brisbane. The call sign was VL4EW. This set was removed from service in 1964 and a 50 Watt SSB transceiver was installed in the new building. With the conversion of the station to unattended operation, the emergency equipment was removed and the aerials dismantled in 1975.
In 1957 the old Skelley generator was replaced by a Ford V8 petrol engine driving a Hodson and Gault 25 kVA 3 phase alternator. The recovered set was transferred to Cairns Division for use elsewhere. This new machine survived until 1966 when a 30 kVA Lister type 127HAG14 driving an Electric Construction Company generator was installed in the new transmitter building. The Hodson and Gault set was sold locally to J. Cole of Mount Garnet.
Line Foreman Cyril Hayward and his team of radio linemen installed a rhombic aerial in November 1957 for use in receiving the Brisbane high frequency transmissions from VLQ9 and VLM4 for emergency rebroadcast purposes. While there, they examined the main aerial and reported on its limited life expectancy. It was cleaned and repainted, but plans were soon being made for its replacement. It was an interesting structure. To a height of 260 feet the mast was 8 inch diameter steel pipe. The top 96 feet was 6 inch diameter. At the transition level a system of cross trees provided stabilization for the top section. There were seven sets of guys below this, in four directions.
Brisbane PMG Workshops fabricated the fittings for a new 200 feet high, 6 inch diameter mast which had been designed by Ron Tolmie, Engineer of the installation Division and Clyde Manuel, mechanical designer of the Brisbane Drafting Section. This pipe was galvanized and pole steps were fitted. The old mast had to be ascended in a bosun’s chair.
The removal of the old mast was under taken by Duncan Russell-Hall in June 1961. All guys on one side were replaced by temporary wires and terminated with one attachment at an outer anchor block. When this was cut with any oxy-acetylene torch, the mast collapsed, generally in the opposite direction, although fragmentation occurred and lengths of pipe fell in unexpected areas.
The new 200 feet long pipe was screwed together on levelling supports and raised from the horizontal using a 70 feet long wooden jury pole. Due to the excessive length to diameter ratio, the lifting of this mast was a very delicate operation.
The lines team were Duncan Russell-Hall, Albert Ray, Percy Crouch, Tony Scott, Alan Elvis and George di Bondi.
During this time 4AT’s transmission was maintained with the use of a rhombic aerial, rather inefficient, but not required for very long. The old coupling box was refurbished and soon the new mast was in service.
In mid 1961 the Minister approved a power increase for 4AT, from 500 Watts to 2 kW and a pair of STC transmitters, 4SU-55A/S, each capable of 2 and a half kW was ordered. They were to operate as main and standby in a new building, plans for which had been approved in late 1960.
The valve line up for these transmitters was oscillator 807, buffer 807, driver QB3/300, modulated final amplifier 3x2500F3. The audio side was push pull throughout. 1st audio EF37A, 2nd audio 807, driver 807 and modulator 4/1000A. High tension supplies were from silicon diode rectifiers.
A contract was let in August 1962 with N. A. Kratzmann (N.Q.) Pty Ltd for this new transmitter building, and it was ready for installation work in mid 1963. The structure was of brick with a galvanized steel “Kliplok” roof.
At this stage, the new transmitters arrived in Cairns on the ship “Burnside” and the installers with Jim Plunkett in charge began work. The system was ready for use on 20 April 1964, with a new 200 Ohm 6 wire transmission line to the aerial and a new coupling unit.
A field strength survey of the station on its new aerial and power was made later in the year by Ken Hobson, technician of the Radio Laboratory.
Within two years, approval was given for 4AT to operate on 4 kW by day and 2 kW by night and Jim Plunkett’s team installed an STC combiner type 792SU-3B. In July 1972 approval to use 4 kW day and night was given and both transmitters were permanently operated into the combiner.
Engineer John Searle was responsible for the transmitters and combiner installations in the new building.
Anticipating the future unattended operation, a Siemens and Halske time clock was installed to switch the transmitters on and off. Unattended operation was actually begun in 1973 after the installation of Cutler-Hammer “lnterscan” remote control equipment, with its control terminal in the Cairns Radiocom Office at Hartley Street. In 1986, control was taken over by the staff of the new Broadcasting Branch Depot in Cairns.
A standby aerial was provided in 1968. It was a steel lattice triangular section mast of 2 feet side dimension. This was one of three supplied by R. W. Edmondston of Marrickville N.S.W., and was 125 feet high. Eight top loading wires were connected, 71 feet long at 45 degrees. Part of the main earth mat was removed in the vicinity of the standby and replaced with a restricted 60 wire mat. Engineer John Searle was responsible for the provision and commissioning. Radio line staff erected the structure and built a 6 wire transmission line.
In May 1972 the frequency was changed to 720 kc/s and before long complaints of reduced signal in the outer regions of the service area were made. The local commercial 4AM frequency 560 kc/s had the advantage of a lower frequency, 460 kc/s (sic, 560 kc/s), and a directional aerial which gave signals a boost in some directions, so that 4AT showed up badly by comparison.
Advice was received in September 1973 that the Australian Broadcasting Control Board had approved the replacement of the 200 ft aerial with an antifading mast and the full time operation of 4AT on 4 kilowatts.
The design for the new aerial was worked out at Broadcasting H.Q. in Melbourne and consisted of a 455 feet high lattice steel tower, top loaded with a coil and a number of sloping “umbrella” wires, to give an effective electrical height of about a half wavelength. This was designed to minimise radiation at high angles and reduce night time fading on the limits of the service area. The mast was supplied by Good Engineering Pty Ltd of Healesville, Victoria.
QSL card from 4AT for reception on 720 kHz in New Zealand during 1981. © Radio Heritage Foundation, Laurie Boyer Collection.
The mast was of 1 metre triangular cross section, guyed in three directions at six levels. After final tests, the top loading wires were set at 100 feet each and the top coil adjusted to give a node height of 120 feet. Six top loading wires were used with a small amount of top coil.
Checks on fading in the lnnot Hot Springs area 30 miles from 4AT showed very little night fading.
Radio linestaff under John Wright dismantled the 200 feet pipe and erected the new Hardinge mast in its place. Electrical adjustments were made by engineers Paul Chippendale and Doug Sanderson, assisted at times by Dave Laing and Garry Waite, technicians. Queensland Engineering Report QB431 was prepared to cover the installation and adjustment of this aerial. The coupling equipment was upgraded by technician Bob Perkins.
The figure of merit of this radiation was measured and found to be 208 millivolts per metre at one mile for 1 kW. This is little better than a good quarter wave mast but consistent with short, top loaded aerials. The high angle radiator however, appears to be small, which was the desired result. In January 1979 a field strength survey of the station’s service area was made by Peter Tilley, technical officer of the Broadcast Operations staff. A contour map QK2672 was prepared.
Telecom obtained permission in 1982 to use the 4AT site as one end of a high frequency radio telephone circuit to Mornington Island. Two log periodic aerials were erected by Radio Section line staff, one for receiving and one for transmitting, and a 100 Watt transceiver was mounted in the transmitter hall.
After the station became unattended, the residence was occupied by Telecom staff employed in Atherton, but eventually the Department of Communications agreed that it was becoming a maintenance liability and should be sold. This was done and the building was removed from the broadcast property and re-erected by the buyer on his property nearby in 1986.
Originally published in On Air, by D.G. Sanderson, 1988, available on WikiBooks under Creative Commons ShareAlike 3.0 Unported (CC BY-SA 3.0) license.