The Voice, Telemetry and Television pictures of the Apollo 11 Moonwalk were relayed from the Parkes Radio Telescope to Sydney via the PMG’s broadband radio (microwave) network.
Overseen by the PMG, technicians from the PMG (Postmasters General Department) and AWA (Amalgamated Wireless Australasia) installed the necessary microwave links to get telemetry, which included voice and the slow scan television, from the radio telescope to Sydney Video at the OTC gateway exchange at Paddington in Sydney.
The closest point of entry to the PMG microwave network was the radio tower at Mount Coonambro, some 28km SE of the telescope and ESE of Parkes township (148°20'01"E, 33°15'06"S).
In order to link to Mt Coonambro, two portable microwave links were installed on the link tower adjacent to the Radio Telescope –
• an AWA 7GHz portable outside broadcast system,
• and an EMI ML6B system (using 4 foot diameter mesh-wire dishes) loaned by Sydney commercial television station TCN-9.
One was prime, the other a backup. Once installed, the system was tested for several weeks before the mission. (See below for Warren Berkery’s notes on installing that link.)
From Mt. Coonambro, the microwave signal went via a 4GHz link to the PMG radio tower at West Orange, and then via 6GHz link to the PMG radio towers at Yetholme, Blackheath and Kurrajong South. From Kurrajong South, the radio link went to the Redfern Radio Terminal in the inner southern suburbs of Sydney – and thence to Sydney Video at the OTC gateway exchange in Paddington.
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An overview of the microwave signal path from the Parkes Radio Telescope to Sydney Video for the Apollo 11 EVA voice, telemetry and television. Larger. PDF version.
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Geoffe Foote, responsible for the technical oversight of the Parkes to Sydney microwave links, explains:
My role during the Apollo 11 mission was that of the team-leader of a small group of Technicians (Technical Officers) from the Postmaster General’s Department’s Radio Section, who were responsible for the transmission of the data and television signals from the Parkes Telescope to Sydney from where the signals were sent to Mission Control at Houston, USA, via normal (satellite) circuits and thence to the rest of the world (in the case of the TV pictures).
Other groups of PMG Technicians and Engineers (e.g. design, installation, external plant, and local staff) and an AWA staff-member were also involved.
A similar arrangement was provided between Honeysuckle Creek tracking station and Sydney.
At Parkes Telescope the signals were carried on coaxial cables from the Telescope building to the “link tower” (the old one not the newer one next to it) where two microwave radio links were temporarily installed between the link tower and the PMG radio repeater at Mt.Coonambro east of Parkes township.
From there the signals were sent to the PMG radio terminal at Redfern in Sydney through PMG radio sites at West Orange, Yetholme, Blackheath and Kurrajong using existing radio links which, in some cases, had to be specially modified for the purpose. In addition an ‘order wire’ speech circuit was provided for operational use. All of these facilities were also used for later Apollo missions.
A team of PMG engineers, technicians and external plant staff from Sydney were heavily involved in the design, installation (including testing) and ongoing operation of the microwave links. As the Supervising Technician from the PMG Radio Section in Sydney who was responsible for the technical oversight of the Parkes-Sydney microwave links for the mission I would like to present the following extracts from my 1969 diary:
19/6/69 – PMG radio technicians Garry Wilkinson (GW) and G.Foote (GF) arrived from Sydney and met Vic Cowenberg (VC) from AWA at Parkes Telescope and carried out video tests to Coonambro on microwave links previously installed by PMG installation staff and AWA (one of the links was AWA and the other was EMI on loan from TCN9). Interference was present on AWA link at Coonambro from FV8 bearer.
20/6/69 – GW and GF carried out video tests from Coonambro to Redfern radio terminal – all OK – returned to Sydney.
23/6/69 – GF and PMG radio engineers R. McCulloch (RMC), and V. Audet (VA) arrived from Sydney and inspected Telescope – Coonambro microwave links.
24/6/69 – VC and Maurie Menier (MM) from AWA and GF changed frequency of AWA link due to interference.
25/6/69 – GW arrived and installed video distribution amplifier. Faulty control cable replaced on AWA link at Telescope.
26/6/69 – Investigated hum on coaxial cables between Telescope building and E/W tower. All returned to Sydney.
27/6/69 – Sydney – acquired further equipment for Parkes
29/6/69 – GW and GF arrived from Sydney in PM – further hum investigation.
30/6/69 – GF at Telescope GW at Coonambro – fixed hum problem using ABC transformer and AWA VDA's – installed order wire TX/RX in E/W tower.
1/7/69 – GF at Telescope GW at Coonambro – Replaced faulty EMI link – installed order wire talk-back unit.
2/7/69 – GF and GW at Parkes and Orange.
3/7/69 – GF and GW at Parkes. Returned to Sydney in PM.
11/7/69 – Sydney PMG Apollo 11 conference – present GF, VA, R.McIlwraith (for Honeysuckle Creek links), L.Williams (OIC Redfern).
13/7/69 – GF travelled to Parkes.
14/7/69 – GF at Telescope – Tests Parkes – Houston.
15/7/69 – GF at Telescope – Tests Parkes – Houston.
16/7/69 – GF at Telescope – GW at Coonambro – Tests Parkes – Houston.
17/7/69 – GF in E/W tower at Telescope – GW at Coonambro – Mission in progress.
18/7/69 – GF in E/W tower at Telescope – GW and J. Bagala (JB) at Coonambro – Mission in progress.
19/7/69 – GF in E/W tower at Telescope – JB at Coonambro – Mission in progress.
20/7/69 – ditto.
21/7/69 – ditto – critical period.
22/7/69 - Rest day
23/7/69 - GF and JB cleaned up and returned to Sydney |
Note – During the above, local Parkes technicians were present at the Telescope and Coonambro on various days. The AWA staff were also present on various days. I did not record all of these dates in my diary. In addition to the above considerable work was required by PMG staff at other PMG radio sites (namely Coonambro, West Orange, and Redfern) to enable the transmission of the signals between Parkes and Sydney.
– Geoff Foote.
(With special thanks to Geoff Foote for permission to reproduce his notes here. And thanks to John Sarkissian at Parkes for the contact.)
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This schematic of the links from Parkes to Redfern (in Sydney) was passed on by PMG technician, Gordon Bennett to John Sarkissian at Parkes in 1999. John photocopied the chart in A3 segments and it was reassembled by Colin Mackellar.
The schematic had been commissioned by Geoff Foote.
Click on the portion above to see the full chart (500kb) or here for a larger (2MB) image.
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The two dishes on the old link tower at the Parkes Radio Telescope.
The TCN-9 EMI ML6B 4GHz link with the wire mesh dish is at the bottom of the picture. The AWA 7GHz link is at top.
Image combined by Colin Mackellar from two frames of film taken from an Australian Information Service film found by John Sarkissian showing the preparations at Parkes.
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The Parkes to Coonambro microwave path as recalled by Warren Berkery
Personal background:
Warren Berkery served a technical traineeship at AWA Ashfield from 1956 to 1960 and studied for the E&C Certificate and TVCoP.
I served as a technician with TCN9 television from 1960 to 1964, then as a Technical Officer with AWA Woomera from 1964 to 1968. I served as a team leader and console operator on the FPS16 tracking radars at Red Lake and Mirikata, delivering real time precision 3D position data on WRE and DoS missile testing, research rocket launches and ELDO test launches.
The Red Lake FPS16 was also a critical site involved in NASA Project GEMINI launches and early project APOLLO tests.
In late 1968 I decided to return east for family reasons. I applied for a position at Honeysuckle Creek, but do not recall an offer of work, so did accept an offer to return to TCN9 as supervisor of Outside Broadcasting.
In this role, I was responsible for operation of portable microwave links.
During 1969 a senior telecoms engineer, who I recall as Fred Hailstone (or similarly meteorological surname), contacted the TCN Chief Engineer, Les Free querying the availability of a TCN portable microwave system over the period of the Apollo 11 Mission to integrate the Parkes Radio Telescope into the NASA network.
The TCN OB links were EMI ML6B ‘portable’ microwave link systems. ‘Portable’ was somewhat of a euphemism, with a complete system weighing in at about 600kg. The operating frequency band was 4460 to 4580 MHz continuously tuneable, transmitter power was 3 watts, gain of the 4ft diameter open mesh parabolic dish circa 28db and Rx NoiseFigure 18db. This was the way of the world circa 1969.
But the ML6B was a proven performer over long haul paths. It served the Mt Buffalo to Mt Blackjack path (160 km+) for the 1960 Melbourne Cup pool telecast without a hiccup.
Fred H took the specs on board, calculated the path loss and Rx field strength as well as the Fresnel zone clearance and agreed to the PMG’s installation from Parkes RT to the PMG site at Mt Coonambro, thence into the PMG bearer system to the NASA control centre at OTC Paddington.
My physical involvement apart from delivering the 600kg package to somewhere in Sydney was to travel to Parkes and to Mt. Coonambro to tune the Tx and Rx klystrons. The only occasion I recall where OB link installation was a collar and tie event.
Fred H also commissioned a second independent link system. This was an AWA 7GHz OB portable system provided by AWA with installation supervised by “Maurie” Menier, a well known character in the TV Engineering field in the era and a pleasure to work alongside.
I was informed in the lead up to the landing that while the AWA link gave marginally better S:N performance, the EMI gave superior hum and base-line performance and was selected as prime on that basis.
So when I viewed the moonwalk in Studio 1 at TCN TV in Sydney, I knew that I had made my contribution to the major event of the era.
– Warren Berkery.
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This photo of the TCN-9 EMI ML6B 4GHz links in use at Red Hill in Canberra was supplied by Ian Mackenzie. The links were regularly used to help telecast election results. |
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The Blackheath tower in January 2009. It has quite a bit more on it now than it did in 1969. Photo: Colin Mackellar. |
