Technical Information
RNZI has two transmitters – a 100kw analogue transmitter and a 100kw
digital capable (DRM) short-wave transmitter.
Technical Manager
Adrian Sainsbury
Our transmission site is at Rangitaiki, 41km east of Taupo in the centre of
the North Island of New Zealand. The coordinates are 176.25E and 38.50S. Audio
is fed to the transmitters by a digital link from the studios in Wellington,
400 kms south of Taupo. The transmission operation includes a control and
telemetry system operating through a standard RS232 computer port. The site
is unmanned and is controlled from our Studio in Radio New Zealand House,
Wellington.
The THOMSON Broadcast and Multimedia digital capable transmitter was installed
in 2005. It is used primarily to provide a good quality signal for relay by
local Pacific radio stations.
The analogue transmitter was manufactured by Thompson CSF of France and installed
in 1990. It has an output power of 100kw and is equipped with three transmitting
tubes; 2 x TH581 with hypervapotron cooling and one TH581 with air cooling.
Our studios are located in down-town Wellington. At the start of 2000 we moved to a new digital system which has almost completely replaced tape for all programme making and broadcast tasks.
RNZI Antenna
We operate two high frequency and two low band antennae manufactured by T.C.I. of California. One of each beams 35 degrees and one of each beams 325 degrees. They can be driven individually, or when fed in parallel the beam widens to 140 degrees.
HR
2/4/0.5 is a five band curtain antenna with a frequency range of
9.5 to 17.9MHz.
It consists of 8 folded dipoles arranged in two columns of four dipoles. The average angle of elevation is 10 degrees and the gain is 17db at 9 MHz which gives an ERP of two megawatts rising to 20 db at 17MHz which gives an ERP of five megawatts in broad terms. In March 1993 the low frequency antenna was installed.
If you wish you can click on the picture for a larger image.
HR
2/2/1 is a four band dipole curtain antenna with a frequency range
of 5.95 to 12.05 MHz.
It consists of four dipoles arranged in two columns of two dipoles. The average take-off angle is 12 degrees with a gain of 16 db at 6 MHz increasing to 19 db at 12 MHz. The antennas are fed with 300 ohm open line feeders with a complex matching and switching system.
A large reflecting mesh forms a backdrop to each antenna array and the tension on the dipoles is maintained with a system of pulleys and counterweights.
The 35 degree beam covers the South Eastern Pacific, and North America. The 325 degree beam covers the South Western Pacific, NE Australia, Japan, China and Europe.
With the antennae combined, virtually all the Pacific Basin is covered.
Gallery
Radio New Zealand Transmission Engineer Andy Anderson shows off a high power water cooled valve, water cooled inductors and capacitors. Also a blower for the air cooling and the transmitter output BALUN.
This motor driven coaxial switch is controlled by the automation system and switches Tx1 or Tx2 to the antenna. By default, whichever transmitter is not connected to the antenna is connected to the dummy load.
Antenna maintenance work in progress.
This cabinet contains the control system for the transmitter, including the ECOS2 computer, the modulator and all the servomotor drivers.
Transmission line (stub) combiner used to combine two 100kW transmitters on 6 and 7MHz to one antenna.
Transmitter building, 50 ohm un-balanced feeders, tapered line BALUN's, balanced transmission line switches, and power dividers.
This motor driven coaxial switch is controlled by the automation system and switches Tx1 or Tx2 to the antenna. By default, whichever transmitter is not connected to the antenna is connected to the dummy load.
