1953: Himatangi Radio opens
The Himatangi Radio control console was installed in a central position in the transmitting hall adjacent to the two London telephone and telegraph transmitters. It allowed the operating technician to gain instant access to the input line of each of the various transmitters as well as a sample of the radio frequency output from each transmitter – an essential feature when it came to circuit assessment or fault diagnosis.
The above photograph shows the control console manned by a technician on shift duty. The jack field and drop cords allowed him access to the input traffic line to each transmitter while the adjacent volume indicator showed the input level of signal from the particular remote traffic terminal.
The left hand units allowed a sample of the radio frequency output from each transmitter to be monitored for transmission quality and level. Two telephone dials allowed him access to the remote traffic terminals in Wellington and to the local PABX telephone exchange, while all circuit events were recorded in the station log book using world wide Greenwich Mean Time.
In the background can be seen the individual cabinets of the 50 kilowatt London telegraph transmitter.
A transmitter was installed for the new radiotelegraph and telephone service to Vancouver. The Marconi HS51 had a rated output of 32 kilowatts PEP on single sideband. This transmitter occupied considerable floor area and required a separate automatic fire-protected sealed room to house its high current rectifiers and power transformers.
A notable feature of the HS51 transmitter was the final output valve Marconi Type BR161. This impressive looking valve was a forced air-cooled triode fitted with a compact array of welded copper cooling fins and requiring forced air cooling at a volume of 20 cubic feet per minute. This air flow had to be started before the application of any supply voltage to the valve and continued for at least one minute after the supply voltages had been removed.
The operating conditions for the BR161 as an R.F. amplifier were as follows:
Filament voltage: 9 volts
Filament current: 175 amperes
Anode voltage: 12,000 Volts
Anode power: 15 kilowatts
Weight: 56 lb (26 kg)
At no time during the switching on process was the filament current to exceed 450 amperes.
Information from George King