And like I said the other day it is being used to look for Asylum seeker boats at the moment not aircraft.
OTHR had a display at AVALON AIRSHOW with diagrams, the people said the only way to beat OTHR was to fly TANGENTIALLY, which correct me but according to the great map above the track was just about tangential to the transmitter site and at the limit of the somewhat low powered Harts Range NT.
At extreme range the backscatter returns would determine the resolution, and a plane makes a small fast target boats are slower, bigger and better and what OTHR was designed for..
REF below.........
This paper presents an overview of ship detection by high-frequency (HF) skywave backscatter over-the-horizon radar (OTHR). Ships have been detected at ranges of 2000 km or more by OTHR that uses sufficient resolution in the radar spatial and Doppler frequency domains. The HF sea-echo Doppler spectrum limits the target signal-to-clutter ratio (SCR), as a function of the ocean wave-height distribution, wind direction, radio frequency, and ship target radial velocity. Maximum sea-clutter spectrum purity, and hence larger SCR, is achieved with the use of stable single-mode ionospheric propagation. Real-time measurement and interpretation of ionospheric propagation features therefore must guide the choice of OTHR operating frequency. Experimental data recorded at the ONR/SR1 Wide Aperture Research Facility (WARF) bistatic OTHR in central California demonstrate reliable ship detection in the Northeast Pacific Ocean. WARF transmits 1-MW average effective radiated power, using a linear frequency-modulated continuous-wave (FMCW) waveform, and receives with a 2.55-km broadside array of vertical monopole element pairs. Swept bandwidths as high as 200 kHz have been used. Sufficient spectral resolution is achieved with a coherent integration time (CIT) of 12.8 s. Longer CIT, and autoregressive (AR) spectral analysis techniques such as Marple's algorithm, have been used to improve Doppler resolution.
Published in:
Oceanic Engineering, IEEE Journal of (Volume:11 ,
Issue: 2  
