Black Mountain Tower

April 28, 2017  •  Leave a Comment

 

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.

 


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