By Frank Barlow ZL2NB
During the war years there were a large number of covert radio stations and listening posts scattered throughout the world. It would probably come as a surprise to most that there was such a station in the pleasant grape-growing province of Marlborough – a long way from the immediate war zones. It is the operation of this station I want to tell you about.
During the war years, when I was at Awarua Radio on the High Frequency Direction Finding watch, a station was linked into the landline (N7) connecting the three New Zealand Direction Finding stations: Awarua (ZLB), Auckland (ZLF) and Waipapakauri (WPP).
This new station was connected towards the end of 1942 under the call-sign RNW, which was the Post Office call-sign for Renwicktown, near Blenheim.
We were told little about its function except that it was a Naval W/T station and that we were to co-operate fully with it.
Nevertheless, with the arrogance and ignorance of youth we were somewhat chagrined to learn that the station would be staffed by the Womens Royal New Zealand Naval Service (WRENS). However, human nature being what it is, we found that the Wrens were all competent operators, as fluent in the Japanese Katikana code as ourselves, and they soon became absorbed into the team.
Our job, as part of the Pacific-wide US Navy’s D/F net, was to take radio bearings on enemy signals that were radioed to us from the US Pacific Fleet’s Headquarters (NIT) in Hawaii, and later Guam. RNW tracked around with us on the frequencies and call-signs received from NIT, but we never did quite know what they were doing, or why they were there.
Now, almost 55 years later, having met up recently with two former members of the Rapaura station as it was known then, their secret function has been uncovered. The Rapaura Naval W/T station was set up on the banks of the Wairau River in late 1942, and all the personnel involved were held under an Oath of Silence from the Ministry of Defence until 1982.
The station was established as an REB station, which are the misleading initials for an RFP Radio Finger Printing station.
This involved photographing signals which came up on an oscilloscope and examining the developed print in minute detail for any peculiarities in the received waveform. These would then be compared with previously recorded photographic strips to see if there were any similarities which would enable the identity of the station or vessel to be established.
The Rapaura station itself was a two-storey farmhouse taken over for the duration of the war by the Ministry of Defence. It was at the end of a long no-exit road at Rapaura, terminating on the banks of the Wairau River.
The house was altered to allow an operating room downstairs for the operators and radio equipment, and sleeping quarters upstairs for the eight Wrens who would be staffing the station. The area surrounding the house was enclosed with a six-foot high, barbed wire fence, with a locked gate, and security was provided by a detachment from the Guards-Vital Points, camped on the site.
It was an ideal radio receiving situation, away from all interference. There was a clump of tall poplar trees close to the house and these were used to provide masts for the inconspicuous aerial, which was shot up by bow and arrow! The equipment was based around a special receiver incorporating an oscilloscope and movie camera, known as REB 2, which had been sent out by the Admiralty, London.
Also provided were two Collier and Beale HRO type receivers, fitted with oscilloscopes.
This equipment was installed by an ex-Post Office telegraphist who was a Leading Telegraphist in the RNZVR. He remained at the station to instruct the staff in the Japanese Katikana code and left when they were proficient.
The operating procedure was to tune into the frequency and identify the callsign which has been signalled from Awarua by the landline. The signals were checked on the oscilloscope attached to the standard receiver for photographic suitability. If suitable, a button was pressed which brought into operation the REB 2 equipment which then started photographing the waveform of the oscilloscope.
Later, when the film was developed, the Classifier examined the films in detail looking for imperfections such as harmonics, damped waved, key-relay effects and anything else peculiar to that transmitter. In many cases the operator’s style of sending could be recognized and this would be a further clue to the station’s identity.
The photographic strip details were recorded, given a file classification and stored for future reference. Once a file had been built up the station could be identified by the signal it emitted and the style of sending. This meant that no matter how often the callsigns were changed – and the Japanese changed theirs daily for a while – the station or vessel could be identified irrespective of call-sign.
The operators worked during the night, 6 pm to 6 am, on four-hour watches, and the classifiers during the day, examining the photographic strips that had been received overnight. If there was incoming traffic of importance during the night or if it was busy, the operators would thump on the ceiling with a broom handle to wake up the sleeping classifiers to bring them down to attend to the urgent traffic and clear the filled cassettes. The results of the classifiers’ analysis would be suitably coded up and telephoned to the Navy Office in Wellington over a Scrambler (inverted speech) telephone.
There were other REB stations set up by the Admiralty, the one in the UK being responsible for identifying the German Pocket Battleship Bismark when it broke out into the North Sea and was ultimately sunk by the Royal Navy. There was another REB station at Sri Lanka (formerly Ceylon) and possibly others.
The Japanese advance southwards was blocked by the Battle of the Coral Sea in May 1942, and their offensive power effectively broken four weeks later at the Battle of Midway. Japan was on the defensive and their large, ocean-going submarines were no longer able to roam at will. A considerable number were used to re-supply their isolated garrisons under Allied blockade in the Pacific.
Enemy radio activity steadily dwindled and in May 1944 the Rapaura Naval W/T station was closed, with the staff being transferred to Navy Office, Wellington, to work in the Intelligence and Communications sections.
During its operation, the Naval W/T station Rapaura (RNW) gave a valuable insight into enemy signals from forces that were menacing our shores at that period. It is to the credit of the Wrens that this particular specialized service was performed with discipline, diligence and in total secrecy. No doubt other wartime radio communications services were performed by women of the Armed Services and it would be interesting to hear about them.
Thanks are due to Bunty Longuet and Philippa Corkill, both Leading Wrens at Rapaura Station, for their information and recall of events long ago.
[Originally published in Break-In, December 1996]