Raoul and Campbell Islands radio circuits

By Rex Johnson

Rex JohnsonDuring the period 1969-1974 I was based at the New Zealand Post Office transmitting station Himatangi Radio as a Radio Technician.

One of our roles was to support communications with Raoul Island and Campbell Island.

Himatangi Radio (transmission) and Makara Radio (reception) near Wellington provided the radio links to Raoul and Campbell Islands
Himatangi Radio (transmission) and Makara Radio (reception) near Wellington provided the radio links to Raoul and Campbell Islands. Google map.

Being a meteorological station, the key requirement for Raoul Island was to provide three-hourly updates of weather conditions to the Meteorological Office in Wellington. So in the dark hours of night, the early hours of dawn, or in the middle of driving rain, Raoul staff were up and about, first taking the current ‘met’ readings, then relaying that information by radio.

This recording activity was also happening at other New Zealand locations. Where Met staff were not employed there might only have been a single daily reading taken by whoever was on site. These were the types of readings taken at Government facilities such as lighthouses or NZPO radio stations. Both Awarua Radio and Himatangi Radio were responsible for taking daily weather records. During World War 2, coast-watchers in the Auckland Islands and Campbell Island also reported weather conditions.

In fact, the valuable reports coming from the sub-Antarctic Islands led to the establishment of a permanent meteorological base on Campbell Island after the war. That service continues (as of 2016), although is now an automated monitoring and reporting system.

At Himatangi Radio transmitting site, the NZPO Makara Radio receiving site, the NZPO Overseas Control Terminal (OCT) and at the Met Office – the latter two being in Wellington – there was regular activity every three hours to collect weather data from Raoul and Campbell Islands. In the 1969-1974 era the data was passed by voice, with the NZPO establishing radio contact with the islands, the receive and transmit circuits being combined into a single telephone circuit at the OCT where it was extended as a regular telephone call to the meteorologist in the Met Office.

The procedure was for the OCT to ring Himatangi and Makara to request setup of a circuit – either Campbell or Raoul first. The OCT would put a ‘transmission circuit adjustment’ call loop on the outgoing line to Himatangi to modulate the transmitter so the remote Met staff could tune their radio to it. At Makara they would listen for a traffic setup call from the island and tune to it. Both Himatangi and Makara would ring the OCT to report their services were established. The OCT combined the outgoing and incoming traffic in a telephone terminal unit and extended the call to the ‘overseas services’ section of the toll room where it would be extended to the Met Office.

On conclusion of the call, the OCT would take back control of the circuit, then call Himatangi and Makara to change the circuit to contact the other island. The setup and connection activity was repeated and ultimately the OCT would advise Himatangi and Makara to close down the circuit. Three hours later it would all happen again.

Redifon transmitters for Chatham Islands and Raoul Island at Himatangi Radio, c1970
Redifon transmitters for Chatham Islands and Raoul Island at Himatangi Radio, c1970. Photo: Jon Asmus

The process at Himatangi Radio was for a designated officer to be on duty at the main control console. The console had two ‘order-wires’ or direct telephone lines to Auckland and Wellington control terminals and it was on the Wellington order wire that setup instructions were given. The duty technician selected an appropriate aerial for the designated Raul/Campbell transmitter, then turned on the transmitter and checked that the OCT circuit adjustment voice message was modulating the transmitter correctly. He then rang back the OCT to confirm the transmit circuit was in place.

The radio-telephone circuit was transmitted over single-sideband HF frequencies using a Redifon transmitter. The antenna was a reversible rhombic, a highly directional aerial that provided a strong signal in the direction selected. This aerial had been ‘re-purposed’ from previous use on a Vancouver circuit, so was already closely aligned for transmissions to the north of New Zealand and Raoul Island. By the addition of an antenna reversing switch it was possible to ‘turn’ the aerial to achieve a strong signal to the south and Campbell Island. Rhombic aerials were so effective they were used at both Raoul and Campbell Islands too.

During the transmission the technician could monitor the voice traffic to ensure the circuit was operating correctly and be ready for the OCT to request the circuit be switched to the alternate weather station. While able to monitor traffic, it was not often done as the messages were really boring. They consisted of a long series of five-digit number groups being passed to Wellington, which might go on for 5-10 minutes.

Being alert and active at 3am to respond to calls for this service worked most of the time, though there were occasional lapses of attention. It is best that a veil be drawn over those circumstances.

Rex Johnson, ready to spring into action at Himatangi Radio c1972
Rex Johnson, ready to spring into action at Himatangi Radio, c1972. Photo: Rex Johnson

Published: November 2016