Profundum Photography: Blog https://www.profundum.com.au/blog en-us (C) Profundum Photography (Profundum Photography) Sun, 05 Jan 2025 04:41:00 GMT Sun, 05 Jan 2025 04:41:00 GMT Black Mountain Tower https://www.profundum.com.au/blog/2017/4/black-mountain-tower  

As you travel on the Federal Highway into the Australian Capital Territory, there’s a ridge just inside the border, just An artist's impression of the completed tower from the original plans. Note the title - "Post Office Tower". before you cross Horse Park Drive.  As you cross this ridge a vista opens up, stretching from North Canberra immediately in front of you on the right, down to the Brindabellas on the western edge of the ACT.  Prominent in the mid-distance is Black Mountain, and inevitably your eyes are drawn to Telstra Tower, rising from the top of the mountain.  It is the point where you see the tower that you actually feel that you have arrived in Canberra. 

At the start of the Seventies, the communications functions of the future tower were being served by two television broadcast masts on the top of Black Mountain (one for the ABC, completed in 1962, and one for Channel 7, the only local commercial station), and by a relatively small facility on top of Red Hill.  The Red Hill facility had been installed in 1955, and comprised a 39-metre lattice-steel pylon supporting the microwave dishes for a terminal and repeater station for the high-capacity broadband microwave systems between Sydney and Melbourne.  The Post Master General had been under pressure from the National Capital Development Commission for some time to clear the Red Hill facility, on the basis that the pylon would spoil the view from the new parliament house planned for construction on Capitol Hill.  Given the depth of the subsequent dispute between the Post Master General and the NCDC over the design and aesthetics of a substantial tower on Black Mountain, it is somewhat ironic that a key factor in the necessity for the new tower was NCDC’s aesthetic objection to the earlier Red Hill facility.

The original two television towers on the top of Black Mountain. The original RT station on top of Red Hill.The original RT station on top of Red Hill.

Anne Moyal, in her book Clear Across Australia – A history of telecommunications, describes the tower as the brainchild of Sir John Knott.  Knott was the Director General of Posts and Telegraphs within the Post Master General between 1968 and 1972, coming to the role after having served as Australia’s Deputy High Commissioner in London.  During his time in London he had dined at the top of the Post Office Tower, and apparently was inspired by the experience to decide that Australia needed a similar telecommunications facility and iconic symbol of modern communications and technology.

On his return to Australia, Knott despatched Deputy Director-General Evan Sawkins to inspect the telecommunications towers of Europe.  On Sawkins' return, the PMG pressed ahead with plans for a facility that would emulate and rival the best examples seen overseas, requesting the Department of Housing and Construction to prepare a feasibility study in April 1970, and obtaining Cabinet approval in early 1972.  The Parliamentary Standing Committee on Public Works approved the plan in August of that year, fixing tenders for September 1973.  The outgoing McMahon Coalition government approved construction in October 1972.

Not everyone was as enthusiastic about the proposal as the PMG.  The Society for Social Responsibility in Science (ACT), with a core membership of academics from the Australian National University, opposed the construction, and advocated a single steel lattice-work radio and TV mast on the top of Black Mountain, and a continuation of radio-telephony installations on Red Hill.  One of the key lines of their attack on the PMG proposal was that it represented a flawed technology strategy, and the country should not be planning interstate microwave systems because fibre-optic systems would soon do the job better.

Map showing alternative sites in the ACT considered for the new telecommunications tower.

 

The National Capital Development Commission (NCDC), the Commonwealth body responsible for the development of Canberra, proposed a number of reductions in the scale of the tower.  In April 1971 the NCDC proposed that the public facilities “drum” (the upper protuberance planned to contain the revolving restaurant and the viewing gallery) be removed and replaced with a much lower viewing gallery underneath the main drum containing the telecommunications and broadcasting equipment.  Under this proposal, the public facilities drum would be positioned around 18 metres above ground level, and reached by a spiral staircase.  The PMG rejected this proposal as unacceptable, on the basis that it would seriously jeopardise the earning capacity of the tower.    After further negotiation, and while still advocating for a design limited to technical facilities, the NCDC pushed for a reduction in the scale of the public drum, seeking to eliminate one of the floors in an attempt to reduce the bulk of the upper drum, and so its visual impact.  FLC Taylor and WF Brigden, writing in the Telecommunications Journal of Australia in 1981, describe the response of the PMG to these concerns as “… by this time, Telecom was becoming seriously concerned at the delay in reaching agreement”.  It does appear that the PMG’s approach to its proposal was quite intransigent, so the sub-text of this comment is essentially frustration at the NCDC’s inability to see the world from the PMG’s point-of-view.

When the new Whitlam Labor government came to power in December 1972, they brought a clear commitment to protecting the environment.  In February 1973, Cabinet decided that an Environmental Impact Statement was required for all developmental projects involving the Commonwealth.  The first ever Environmental Impact Statement was pulled together “across a weekend” by the PMG in mid-February, and the project steamrolled on.  Taylor and Brigden from the PMG described the Environmental Impact Statement in 1981 as “…attract[ing] strong criticism from opponents of the project, much of which, in retrospect, was probably justified.”

Construction of the tower shaft.

The opposition to the tower launched an ACT Supreme Court Action, ultimately leading to construction being suspended in November 1973 by order of the Minister for Works.

While construction resumed in December 1973, disputation continued through to 1975, including a High Court judgment that concluded that the PMG’s statutory powers extended to incidental matters such as the addition of a restaurant and public viewing gallery into a telecommunications facility.  While it does not appear to have been relevant to the judgment, Justice Jacobs of the High Court took the opportunity to quote from Walter Burley Griffin’s October 1913 Plan for Canberra, as follows:

“Ainslie, Black Mountain, Mugga Mugga, rising almost 700 feet (too lofty and too exposed for building purposes), afford objective points of prospect to terminate great garden and water vistas, with conspicuous positions for future commemorative monuments, and conversely offer points of outlook over a city arranged in an orderly way with reference to them.”

While the “future commemorative monuments” have never been built, these words highlight one reason why the views from the tower are so special – Canberra was aligned to highlight the view of Black Mountain, and this alignment shows when Canberra is viewed from the tower.

Substantial completion of the construction was achieved in 1977, with the tower ultimately being opened by then Prime Minister, Malcolm Fraser, on 15 May 1980.  By then it had cost more than $16.3m, the equivalent of around $80m today.

In the three weeks following the opening of the tower, Telecom Australia conducted the imaginatively-named "Operation School Kid", under which some 26,000 ACT schoolchildren and 870 of their teachers were given a free visit.  This was accompanied by "Operation Shuttle Bus", under which a free bus was provided from the Canberra CDB to the tower for the first four weekends after opening, allowing members of the public to inspect the tower for $1 per adult and 20c per child.  Some 16,200 adults and 6,000 children availed themselves of the opportunity.

Extract from original plans from 1973 - note the title of "Post Office Tower"

 

 

 

 

 

 

 

 

 

 

 

 

 

Network and historical context of the tower

There is much that could be said about the network demands, commercial factors and technological evolution that led to the building of the tower, but for present purposes it is probably adequate to capture some key themes:

·         Demand for telecommunications trunking capacity between Sydney, Canberra and Melbourne increased steadily (and sometimes rapidly) with growth in the economy and the increased integration of telecommunications into commerce.

·         Canberra was an important link not only in the telecommunication connections between Sydney and Melbourne, but also in the connections to Cooma and the South Coast, and to the facilities at Orroral Valley in the south of the ACT.

·         The importance of telecommunications links between Canberra and the two major state-capitals increased with the build-up of Commonwealth government functions in Canberra from 1927 onwards.

·         Trunking technology progressed from open-wire copper-pairs strung between poles, into radio links and co-axial cable.  Co-axial cable offered greater scope for capacity and cost-effectiveness in serving regional communities along the route, while microwave links offered greater flexibility and speed of implementation.

·         Demand for telecommunications trunking capacity increased rapidly with the advent of television in 1956, driving demand for the ability to relay television programming to regional stations.

·         The introduction of crossbar switching technology delivered exchange automation and the possibility of subscriber trunk dialling (STD).  STD was only possible where there was adequate trunking capacity to meet the as- needed demands of customers.  Without adequate trunking capacity, customers required the services of operators to book calls, and then subsequently connect them once the required capacity became available.  STD functionality became available for Canberra customers in 1962, for Sydney customers calling into Canberra in 1965, from Sydney to Melbourne in 1964, and from Melbourne to Sydney in 1965.

·         Important trunking links required route diversity to deliver security of connection, particularly in a country as susceptible to natural disasters as Australia.  The importance of diversity in relation to Canberra, with its sensitive government communication networks, was reinforced by the Civic Exchange fire in 1961, destroying the exchange building and all the links that went through it.

Structure and layout of the tower

Public areas schematic arrangement - from the original plans Mervyn Cole of the Commonwealth Department of Housing and Construction, writing in the Telecommunication Journal of Australia in 1981, remarked that the design concept for the tower "was for a slim, unobtrusive and economic structure, having the necessary structural rigidity and providing for all accommodation required on the shaft".  Given the tower's undeniable prominence in the Canberra landscape, the reference to "unobtrusive" seems a little optimistic and it's possible that, even after completion of the tower, Cole still felt a reflexive need to defend the design decisions made by the PMG and CDHC.

The starting-point for the design of the tower is probably the required height of the main antenna. Co-masting of the antennas for television, FM radio and mobile and paging required an antenna-height of 63.1m.  To deliver the required signal-propagation, the antennas were specified to be 122m above the peak of Black Mountain.  Given that the tower was located slightly below the peak, the resulting tower-height was 195.2m.

The next key factor in the design is probably the need for the external walls of the equipment drum to accommodate sufficient microwave antennas, with flexibility for future requirements, and the ability to locate the supporting equipment sufficiently close to the antennas to avoid signal-loss for higher-frequency signals.  The intention was to anticipate the requirements for a 50-year operational life, and accordingly the tower was designed to accommodate 14 parabolic dish antennas in each of three directions, with each antenna some 4 metres in diameter.  This requirement dictated the necessary external surface-area of the equipment drum, which in turn yielded the resulting internal volume.  This resulted in a design comprising three floors, one to house the microwave needs, then two for mobile, paging, broadcast monitoring, maintenance and the Television Operations Centre, or TOC. It is worth noting that, in practice, only one of these two additional equipment floors has ever been used to house equipment, and one of the three floors in the equipment drum has been fitted-out with meeting rooms since the time of construction.

Floor schematic

The tower was awarded a Certificate of Merit by the Concrete Institute of Australia in 1979, and the 1980 Civic Design Award by the ACT chapter of the Royal Australian Institute of Architects.

Writing in the Telecommunications Journal of Australia in 1981, Jim McCarthy, a manager in the PMG's Buildings Branch and a one-time NSW editor of the TJA, stated that "The Black Mountain Tower story is unique and unlikely to be repeated."  That rings true - the tower seems to have been a remarkable product of a unique set of circumstances.  With the advent of competition in the Australian telecommunications market, it is very unlikely any operator in the market today would determine that its investment priorities extended to constructing structures of similar scale to the tower.  The current ubiquity and speed of optical-fibre cable mean that the tower's original role in microwave trunking is unnecessary.  With ACT self-government, it is hard to imagine any Commonwealth instrumentality being able to undertake a similarly intrusive project against such widespread popular opposition.

 

 

 

 

 

References:

  • Clear Across Australia – A history of telecommunications, A Moyal,
  • “The Black Mountain Tower – an Introduction”, FLC Taylor and WF Brigden, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “A Historical Review of the Planning of the Sydney-Canberra-Melbourne Trunk Route”, N Smith, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “The Tower Radio Functions and Specification”, LJ Derrick, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “Project Development and Building Facilities”, JF McCarthy, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “Design and Construction”, MF Cole, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “National TV and FM Broadcasting Facilities”, VJ Audet, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “Commercial Television Installation”, RK Burbridge, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • “Buildings and Engineering Services”, MS Pembroke, Telecommunications Journal of Australia, Vol 31, No 2, 1981
  • Johnson v Kent (1975) 132 CLR 164
  • Last Supper for Alto on Valentines Day, goodfood.com.au, 14 February 2014 - http://www.goodfood.com.au/eat-out/news/last-supper-for-alto-on-valentines-day-20130214-2efc1
  • Thom Blake's Historical Currency Converter:  http://www.thomblake.com.au/secondary/hisdata/calculate.php

 

Acknowledgments:

Many thanks to Telstra for providing access to the tower to undertake this project, and in particular to Dave Stewart for both the original suggestion and arranging the necessary introductions to make access a reality.

Thanks also to Justin Thompson of Raine & Horne Commercial, Canberra, for both his love of the tower, and giving up his time to act as a guide behind the scenes.

 

]]> (Profundum Photography) heritage Post Master General Telecom telecommunications https://www.profundum.com.au/blog/2017/4/black-mountain-tower Sat, 29 Apr 2017 07:05:47 GMT The Sydney-Melbourne Co-axial Cable https://www.profundum.com.au/blog/2016/6/the-sydney-melbourne-co-axial-cable The Sydney-Melbourne Co-axial Cable
 
When you drive along the Hume Highway between Sydney and Melbourne, or along the Federal Highway between Goulburn and Canberra, if you pay attention to the scenery, every few kilometres you might just notice a non-descript concrete structure sitting in a paddock just off the highway, looking like nothing quite so much as a misplaced bunker.  They are easy to miss if you aren’t looking for them, but in fact they are one of the few remaining signs of a remarkable achievement in Australian telecommunications engineering – the Sydney-Melbourne Co-axial Cable. 
 
In the words of the editorial in the February 1962 edition of The Telecommunications Journal of Australia:

It is difficult to convey the vastness of the project to those who were not associated directly with the work.  Telecommunications engineering works are not spectacular in nature, and now that the Sydney-Melbourne cable has been laid, there is little visible evidence that the work was undertaken.  Even at the height of the cable construction, the effort extended over such a long length of the route that its magnitude was not obvious.

Nevertheless it involved the laying of 600 miles of cable across difficult terrain…  Some one million tons of rock and soil were excavated for the trench in which the cable was laid, and this represents a major civil engineering effort equivalent to the excavation required in the construction of a large dam…. It was, both in size and complexity, by far the largest work of this nature ever undertaken in Australia.  [TJA, February 1962, p166]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
In the various commemorations at the time of the fiftieth anniversary of the completion of the cable, it was common to see it described as the “NBN of its day”.  The comparison fails in a number of ways.  In terms of cost, the Sydney-Melbourne co-ax cable cost a mere £6.89m – equivalent to approximately $175m in 2015 terms.  The project was completed and the first telephone circuits across the 1000kms of cable were brought into service within 33 months of the signing of the contracts for the work.  But probably what people are trying to say when they throw around comparisons to the NBN is that it was a momentous milestone in the nation’s telecommunications evolution, requiring vision, a certain degree of audacity, and large measures of plain hard work and disciplined implementation.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
In this blog I am going to try provide an overview of the Sydney-Melbourne co-ax cable, the issues it was designed to address and the project to build it, accompanied by historical images from its construction and present-day photos of some of the remnants.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Why build a new Sydney-Melbourne cable?
 
At a superficial level, it may be self-evident that as demand grows, telecommunications systems need to be upgraded and enlarged, but it is worthwhile to dig a little further into the background to the circumstances that led to the decision to build the Sydney-Melbourne Co-ax.
 
The first telephone circuit between Sydney and Melbourne had been opened on 14 June 1907, running over an open-wire system (ie traditional aerial wires strung from poles).  With developments in technology, this route had been upgraded with the addition of ten 12-channel systems – apparently offering the ability to run upto 120 simultaneous calls.   After the end of the Second World War, a large volume of suppressed commercial demand was released, which was in turn reflected in greater demand for telephony.  Accordingly, a further open-wire route was commissioned, adding a further set of ten 12-channel systems.  By 1947, the route was carrying 48 Sydney-Melbourne circuits, 12 Sydney-Canberra circuits and 22 Melbourne-Canberra circuits, in addition to other trunk circuits to other state capitals.
 
Despite this investment and construction, demand for telephony continued to outstrip capacity, and each channel was so valuable that it had to be operated to secure absolute maximum usage.  At least three operators were involved in the handling of each call.  In the first place, there would be a “booking telephonist” who recorded the request for the call, in what was called a “reverted” call system, meaning that you placed your request for a line and the operators would “revert” to you when there was capacity for the call to be made.  When the time came for the call, an operator at each end would contact the parties and bring them to the telephone to wait several minutes for the next available circuit.  At times, it was not uncommon to have to wait 2 to 3 hours between requesting a call and being able to actually make it.  In that environment, things like the transmission of television broadcasts were out of the question.  Significantly more capacity was required.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
So why co-axial?

Which begs the question for most people – what is co-axial cable?  A single co-axial cable has an inner conductor or wire, surrounded by an insulator, which in turn is surrounded by a further tubular conductor that shields the cable.  When a signal is carried on the main inner conductor, the shielding prevents leakage of the signal to neighbouring objects (such as other nearby cables), but also protects the signal from external interference, allowing more faithful transmission of high-frequency signals over a distance.  The “co-axial” refers to the fact that the inner wire and the outer circular shield have the same central axis.
 
The range of options available to the Post Office when choosing the technology for the new trunk links between Sydney and Melbourne included radio, co-axial cable, “quad carrier” cable, open-wire systems, or a hybrid combination of these.

Of these options, co-axial cable and microwave systems offered the ability to relay television programmes.  Open wire systems, basically continuing to add to the existing technology, had limited capacity and high maintenance costs, being exposed to the elements.
 
A microwave system would have involved a network of hill-top radio stations along the route, each within line-of-sight of the next.  This would have been feasible enough, but in order to deliver service to the towns along the route it would need to be combined with additional radio networks, cables or open-wire systems, resulting in significant complexity and much higher costs.

Ultimately, a co-axial cable system offered the right combination of functionality, scope for further development, capital cost and ongoing maintenance costs.

 
The cable that was laid actually comprised six separate co-axial tubes, with each inner conductor having a diameter of 2.6mm, and an inner diameter for the outer conductor of 9.5mm (the metric measurements in Imperial-system Australia attributable to the German manufacture of the cable – more on that below).  In addition to the six co-axial tubes, inside the cable were an additional sixteen “quad carrier” wires, providing 32 wire-pairs for control and supervising circuits, gas-pressure alarms and short-haul carrier systems.  The granite memorial plaques that were laid at Casula and Melbourne to commemorate the completion of the cable record the total diameter of the sheath as "2 inches", but that seems likely to be just a rough approximation.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Repeater stations

There were a total of 118 stations housing transmission equipment along the route from Sydney to Melbourne.  Of these 103 are unattended minor stations (the “misplaced bunkers” mentioned in the introduction), there was a terminal station at each of Sydney South Exchange and Melbourne West Exchange, and then thirteen manned main-repeater stations located at Campbelltown, Bowral, Goulburn, Canberra, Yass, Gundagai, Wagga, Culcairn, Albury, Wangaratta, Benalla, Euroa and Seymour.
 
It appears that a known pilot frequency of 4,092kHz was transmitted on one channel of the cable, and then equipment at each repeater station compared the pilot signal to the known frequency, and any corrections and amplifications were applied to the signals before they were re-transmitted to the next station.
 
 
 
 
 
 
 
 
 
Temperature affected the signal propagation and the performance of the repeater equipment, so the repeater stations were designed to minimise temperature fluctuations.  Walls and the roof of the repeater huts were double-layered, with an air-gap between the layers for insulation, and entry was through a short lobby with two heavy steel-clad doors, one at either end, to minimise air-flow during staff entry.  With external heat the main concern, the two doors were specifically designed with a ventilator grille at the top of the outside door, but at the bottom of the inside door.  The huts are all oriented to face south or south of east, to minimise sunlight entering through the open doors.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The repeater huts were all pre-fabricated from concrete, with outside dimensions of 14 feet by 12 feet (approximately 4.3m by 3.7m), and an internal ceiling height of 8 foot (about 2.4m).  In areas subject to flooding, the huts were constructed with raised floors and external stairs.  
Today, the remaining repeater stations are in a range of different conditions.  In more built-up areas, some of the sites have been sold-off and the repeater huts demolished.  Some huts have been stripped and reused to house equipment for subsequent fibre-optic cables that serve the same Sydney-Melbourne route.  In rural areas, some of the huts have been left unsecured and have been used by humans to camp in, livestock to shelter in, or sometimes just ransacked.  Even where huts have been left secured, as with any unattended shelter in rural areas, they can be colonised by rats who nest in amongst the equipment and scatter droppings and nesting material.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Route

A preliminary route for the cable had been determined in 1950, and this preliminary route had been used for issuing the request for tenders to potential suppliers.  Along this preliminary route, sites for the 13 main repeater stations were selected and locked-in, largely based on issues such as the location of appropriate service centres, and population centres that were intended to be served by the cable.
 
That still left a requirement to determine the route between these main repeaters.  This was done by progressively working down from a number of options chosen from detailed maps and aerial photos, and then ultimately walking the routes using compass bearings, to select the most suitable route.  Generally speaking, the factors influencing route section were a preference for the shortest route, combined with considerations of access, practicability, and security from hazards such as floods, landslips and erosion.
 
From there, an engineer made the detailed route selection for a preliminary pegging party which placed pegs at thousand-foot intervals and at angles in the route.  This enabled the preparation of basic survey plans, allowing repeater sites to be selected so that the process could be started to acquire the sites.  Once the sites had been selected, a detailed final survey could be conducted, with pegging at 100-yard intervals.   The cable was laid from the Sydney end, and weather issues on the New South Wales section gave rise to a need for non-sequential laying – skipping sections that were water-logged or even flooded, and then returning to the difficult sections later when they had dried-out.  This meant that when it came time for detailed surveying and pegging of the Victorian sections, this was done in much greater detail, to allow identification of joints so that cable-lengths could be accurately specified for sections that were being laid out-of-sequence.
 
Once the cable was laid, the route was marked with seven-foot concrete posts.  Each one has a metal plate on the top indicating the identity of the cable, the depth and the direction of the cable-run on either side of the post.  From each marker-post it should be possible to see the next post or the repeater station.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Cable laying
 
Once the detailed cable route had been determined, the cable laying process involved clearing any trees for a distance on either side of the route, ripping a trench along the line of the cable, drilling and blasting any rock material that couldn't be ripped, removing the ripped or blasted rock from the trench, laying the cable on top of an underbedding layer, covering the cable with an overbedding layer, timbering the overbedding, and then completing the backfilling.  In areas where erosion was a concern, earth banks were used to direct run-off away from the cable route.
 
Some 17 rivers and about 120 creeks and gullies were crossed, with the cable being laid under the bed in most cases.  On three major river crossings, such as the Goulburn River at Seymour, the cable was installed in conduit on road or railway bridges, but generally above-ground installation was avoided.
 
The initial plan for laying the cable was that ripping would proceed significantly in advance of the cable route, ripping the cable trench to the required depth of 4 feet.  It was intended that this would enable early identification of any significant rocks in the cable path that might require power-tools or explosives to clear. This approach was taken for the first section from Sydney to Goulburn, until it was discovered that with either rain or soft soil, this sort of pre-ripping led to collapse of the soil for a significant distance on either side of the trench, with the result that the cable-laying or trenching machinery would become bogged, and occasionally the cable route had to be moved to one side to find more stable soil.  South of Goulburn a different approach was taken, with pre-ripping only being done where it was known that it would provide assistance, and then only immediately in advance of the trenching.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Suppliers
 
For the Sydney to Canberra portion of the project, the cable itself was manufactured by Felten and Guilleaume Carlswerk A.G of West Germany.  For the portion of the project south of Canberra, the cable was manufactured in Melbourne by Olympic Cables Pty Ltd as sub-contractor to Felten and Guileaume.  Presumably this arrangement allowed the project to commence without delay, while Olympic Cables equipped their facilities in Melbourne for production.
 
The transmission equipment was manufactured primarily by Felten and Guilleaume Fernmeldeanlagen G.m.b.H. in West Germany.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Cable Pressurisation
 
The Sydney-Melbourne co-ax cable is pressurised using a continuous flow system.  This comprises compressed-air canisters housed at repeater stations, and connected to the co-ax tubes through regulators to maintain a constant pressure.  The purpose of the pressurisation is two-fold.  Firstly, by monitoring the pressure both at the repeater stations and inside the cable, it is possible to detect damage to the cable-sheath, allowing remedial action to be taken before a fault develops.  Secondly, the positive pressure within the cable means that, in the event of a breach of the cable sheath, water ingress is less likely.
 
Originally, the cable was designed to have mercury U-tube manometers installed at 1000-yard intervals, and connected to electrical contacts that would register the air-pressure falling below a pre-determined level.  These mercury manometers were installed for roughly the first 350 miles of the cable from Sydney before testing was able to be undertaken on the first section.  This testing revealed that six out of the ten tested manometers failed.  Investigations revealed that the failures were due, at least in part, to impurities in the mercury being used, resulting in significant innaccuracy in operation.
 
The mercury manometers were subsequently replaced with mechanical bellows contactors, which made a connection between two wires within the co-ax sheath when the air pressure dropped below the pre-determined level.  The bellows contactors were connected with different resistors to assist in identification of which contactor had been triggered, to assist in locating the approximate location of cable-breaks.  At the repeater stations the air-pressurisation equipment gave the ability to inject tracer gas into the cable to assist in identifying the precise location of the breakage.  It appears that the tracer gas would be either radon or freon.  Apparently the freon would be coloured with a dye for visual identification of the cable-break.  Presumably radon was used in association with a geiger counter.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Customer impact
 
Once the cable was in full operation, it was possible for the first time to transmit a live television broadcast between Sydney and Melbourne.  The additional voice capacity delivered not only better quality voice calls, but ultimately the ability to implement subscriber trunk dialling (STD) between the two state capitals, as there was now enough capacity available to meet demand on-demand, rather than requiring customers to book in advance.  Finally, many population centres along the cable route were now able to receive significantly increased capacity and automation of their previously-manual exchanges.
 
 
 
 
 
References

 
1.AH Kaye, "Main Features of the Project", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

2.IS McDuffie, "The Telecommunications Aspects", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

3.JF Sinnatt, "Design of the Cable Plant", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

4.DF Barrie and CH Hosking, "Installation of the Cable", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

5.FJ Harding, "The Gas Pressure Alarm System", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

6.AL Fisher, RJ Clark, RA Colins, "Transport of Cable and Other Materials", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

7.JV Dunn and M Fizelle, "Buildings", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

8.JR Walklate, "Design of Transmission Equipment", The Telecommunications Journal of Australia, Vol 13 No 3, February 1962.

9.JW Pollard, "The Application of Gas Pressure Alarm Systems to Coaxial Cables", The Telecommunications Journal of Australia, Vol 13 No 1, June 1961.
 

 
Acknowledgments
 
Many thanks to the following people for generously giving their time, knowledge, resources and wisdom:
 
 - Janko Radocaj
- Stef Nowak
- David Piltz
- Phill Sporton
 
 And thanks and acknowledgment as always to Brian Mullins and the team of dedicated volunteers at the Telstra Museum Bankstown.
 
 
 A similar photo-blog on the old Port Kembla Exchange can be found here:   http://portkemblaexchange.blogspot.com/
]]> (Profundum Photography) https://www.profundum.com.au/blog/2016/6/the-sydney-melbourne-co-axial-cable Sat, 25 Jun 2016 12:10:45 GMT The Legend of Babe the Plough-dozer https://www.profundum.com.au/blog/2016/6/the-legend-of-babe-the-plough-dozer The story would never have happened if old dozers had any resale value.  But no-one will pay you anything but scrap value for a decades-old second-hand dozer...

Babe the plough dozer first proudly entered service for the Post Master General as a shiny new Caterpillar D9G in December 1968.  Weighing-in at a massive 49 tonnes, she started life laying co-axial cable, including working on the Sydney-Perth Co-ax cable. Babe in her youth

Over the years, as standards have evolved and life has become a little more civilised, she collected a few modifications, such as an air-conditioned enclosed cabin, roll protection, a zero-tension cable-laying assembly and a petrol starter-motor.

As the dozer fleet was modernised, Babe was increasingly moved into semi-retirement, and if she had any resale value she would probably have been sold.

Then in March 2014, the Network Construction team ran into an unusual challenge.  They had to replace a section of fibre-optic cable between Goodooga and Lightning Ridge.  Because of reactive soil in the area, the existing fibre-optic cable had been developing faults.  The shifting soil would pinch and bend the cable, causing breakages in the delicate glass fibres.  The technical advice was that the best way to avoid the problem was by going deeper, below the reactive soil, where there was less movement.  The challenge was that the standard depth for laying cable was only 900 millimetres, and the modern D7 dozers that the team had couldn't get down to the depths required.  In the face of an urgent deadline for completion, it looked like the job was going to require some expensive specialist excavation work, probably requiring multiple passes by different types of equipment.

Then someone remembered Babe.  She came from a different era, when sometimes cable would be laid as deep as 1500 millimetres.  Babe was broken out of retirement, given a thorough service, and brought back to work.  She laid the entire 41 kilometres of replacement cable herself.

Now Babe is back in the depot in Ningi, north of Brisbane on the way up to Bribie Island, sitting there dreaming of cable-runs long past, and patiently waiting for the next one that the youngsters can't handle by themselves...

Babe’s stats
Engineering role: Heavy bulldozer
Propulsion: Caterpillar tracks
Gross power: 385 hp (287 kW)
Drawbar pull: 71.6 tons
Operation weight: 49 tons
Length: 8.1 m
Width: 4.5 m (blade)
Height: 4 m
Speed: 11.9 km/h forward and 14.7 km/h reverse
 
A younger Babe in action laying cable, before installation of the enclosed cabin and the zero-tension assembly.
 
A younger Babe in action, from the cover of a Telecom publication from June 1982.
 
 
 
 
Babe today, in the depot at Ningi. Detail from front of engine Zero-tension cable-laying assembly Engine enclosure Engine and cabin Detail of wheels and caterpillar tracks Detail of step to climb into cabin Front anchor-point Grille over radiator Front view Front mounting-bracket Caterpillar tracks, wheels and running-board Detail of caterpillar tracks Plough mounting at rear. The plough-blade goes into the fitting at the bottom-left, and is held in place by the large steel pin at the top of the fitting. Caterpillar D9G Telstra plant number - "TEL100" Hydraulic fluid reservoir? Muffler Instrument panel inside the cabin. Zero-tension cable-laying control panel. Note the "Designed and manufactured by Automotive Plant - Telecom Australia" Babe came into service in December 1968 - but she still has that "new car smell". An old cable-laying plough. Note the cable-depths welded onto the face of the plough. An old cable-laying tube. The fibre would be fed down the tube to be guided into the trench behind the plough. Front mounting-point. Note the depth of the gouges out of the steel. Detail of caterpillar tracks This appears to be an air-filter housing. Note the faint traces of the stencilled "Babe". An axle housing
 
]]> (Profundum Photography) Babe Post Master General Telecom Telstra cable co-axial coaxial dozer fibre heritage history optic plough telecommunications https://www.profundum.com.au/blog/2016/6/the-legend-of-babe-the-plough-dozer Thu, 09 Jun 2016 22:28:17 GMT