Technical Overview
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. This results in a maximum power of 192kW.
These power levels, whilst they may appear high, are significantly less
than broadcast transmitters (typically 1000-2000kW) and the existing
EISCAT Tromsø heater (1200 kW).
The distributed arrangement is based on a new transmitter design
developed specifically for this project. This solid state design has
extremely low levels of spurious emissions and incorporates high power
filters to minimise out of band signals. The actual levels are indicated
in the attached system specifications. This level of performance will
minimise potential interference problems.
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Parameters |
| Location |
78°9'N 16°4'E |
| Transmitter configuration |
48x4kW solid state transmitters |
| Total Power Output |
192kW |
| Operation Frequency |
11 spot frequencies between 4.45 and 5.82MHz |
| Antenna Configuration |
4x6 array of horizontal, rhombically broadened, crossed dipole 17m above ground |
| Antenna gain |
22dBi |
| Beam width (3dB) |
14°x21° |
| Pointing Direction |
Fully steerable, 360° azimuth, 20° off zenith |
| Power (ERP) |
28MW |
| Modulation |
CW |
| Duty Cycle |
100% |
| Bandwidth |
<100% |
| Spurious emissions |
| Harmonics |
<-60dBc |
| Other |
<-55dBc |
| Polarisations |
O mode and X mode |
The system is designed to operate on spot frequencies between 4.45 MHz and 5.82MHz (the exact frequencies are listed here). A variety of modulation schemes
and power levels will be required according to specific scientific
requirement as described below.
Modulation schemes available
The system has a variety of on / off periods and modulation schemes which can be pre-programed into it. Both schemes can be ran with a O or X mode polarisation and both can run concurrently. The system uses a GPS iridium clock for all experimental timing.
Enquiries regarding specific modulation schemes should be sent to Dr Lisa Baddeley:
e-mail: spear<a>unis.no
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