SPEAR is a vertical looking, HF radar system based on a distributed transmitting
arrangement. The system consists of 48, 4kW solid state transmitters arranged in
a 4x6 array of crossed dipoles:
An ariel view of the SPEAR array
The antennas are held in place, 17m above ground level, by a series of metal masts:
The transmitters will be housed in 6 specially modified shipping containers, with each container housing 8 transmitters. Each container will form a single unit
feeding a 2x2 sub array.
Each individual transmitter
contains its own power supply and control unit. This allows the system to remian operational if a single transmitter fails.
Each transmitter
container contains a common signal generation unit made up of DDS units
allowing individual phase control of the signal at each antenna. This
allows the transmit beam to be steered to any position although the
antenna design limits the useful pointing direction to +/- 20° from the zenith.
There is also an environmental control computer (ECC) located in each of the containers, which controls the ambient temperature of that container. The system is fitted with an adidtional saftey feature by which the ECC must be funcitioning to allow power to the tranmitters housed in that container.
The system is positioned such that its minor axis is rotated 10° west from geographic North (14° west of geomagnetic North).
The array minor axis is shown, marked 'Array north'
For further technical details click here
Pointing Direction
The default pointing direction for SPEAR is aligned along the magnetic field:
- Azimuith: 182.1°
- Elevation: 81.6°
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