see also:

• radio basics

• radar is a system that uses radio waves to detect, locate, and track objects at a distance.
• radar stands for Radio Detection and Ranging, originating from its ability to determine the range (distance), direction, and velocity of objects relative to the radar site
• it is usually line of sight (as with most radio systems) but can be “over-the-horizon” long distance RADAR by bouncing off the ionosphere
• it relies upon a radio transmitter sending out radio waves and a radio receiver (usually at the same location) receiving the radio waves bounced back by objects

• as with radio waves, radar generally works only by line of sight with limited distances (often restricted to hundreds of km), and restricted by heavy rain
• this is the type generally used by weather systems, air craft management systems and the military
• this means that aircraft can evade these radar systems by flying low in valleys

• this is what produces the weather maps of rain and storm superimposed on a geographical map
• the limited distances of radar means that such a map may combine imagery from a number of radars if the view is over 100km from a radar
• the weather map may display rain as either:
  • dBz - actual radar measurements
  • mm/hour rainfall - an estimate of the intensity of the rainfall
• NB. if there is poor internet connection you may be misled there are no storms coming as the geographical map may load but not the radar imagery overlay or it may display just an old cached image
• generally are in 3 frequency bands:
  • S-band (2,700–2,900 MHz):
    • Used for long-range weather observation (up to ~300 km), including the U.S. NEXRAD network.
    • S-band is preferred for detecting severe weather and heavy precipitation because its longer wavelength (∼10 cm) penetrates heavy rain with less signal attenuation
    • Australian examples include radars in Melbourne, Canberra (Captains Flat), Sydney (Terrey Hills), and Newcastle
  • C-band (5,250–5,725 MHz):
    • Commonly used worldwide, especially by TV stations and regional weather services, with an effective range up to ~200 km.
    • C-band offers a balance between reasonable range and manageable equipment size, but is more affected by precipitation attenuation compared to S-band
    • Victorian examples include Broadmeadows, Bairnsdale, Mildura, Rainbow, Yarrawonga
  • X-band (9,300–9,500 MHz):
    • Used for short-range weather radar (~50 km or less), often for specialized applications like airport weather monitoring.
    • X-band radars are more sensitive to small particles but are highly susceptible to signal loss in heavy precipitation
• most radars are Doppler capable
• some radars also include dual-polarisation technology to improve precipitation type detection and storm characterization, with many newer installations in both bands incorporating this capability

• although more expensive, these have a significant advantage over the usual infrared motion detectors in that they can be used behind glass windows (eg. car windscreens) or hidden behind tree trunks, etc, (but do not go through metal)
• perhaps best used for you to carry with you when you leave your camp site to have a chat with others in the camp ground and then could be alerted to a potential thief
• usually use a frequency in the 3.18 GHz to 5.8 GHz range for the radar component
• eg. Lefwesat radar motion detector and wireless receiver for camping
  • has a chime bell which can be silenced and an alert light
  • turn on by holding side power button for 3 secs
  • to pair select the detector number on the receiver (1-6) then press pair on receiver then pair on detector
  • can turn detector on/off via the receiver up to 300' away - receiver will be alerted up to 1/2 a mile away.
  • detector can supposedly detect 14m in front and 3m to each side and can be hidden behind tree trunks, plastic, or glass, but not metal
  • detects ~1.5m BEHIND detector eg. much of inside of car if set to detect outside through the windscreen
    • will alarm if it detects rain hitting the windscreen
  • range is reduced to around 6m in front and 1-2m each side when behind windscreen glass
  • can reduce the sensor range by going into probe set mode and walking around in front of sensor to record the desired sensor area
  • must not be exposed to heat eg. sun on hot days as the 3000mAh li-ion battery may explode - battery normally lasts 60hrs for sensor and 200hrs for receiver
  • see https://www.youtube.com/watch?app=desktop&v=C8wNUqQu9XI online user instructions
  • see https://www.youtube.com/watch?v=Es1_nCvzR-A
  • https://www.amazon.com.au/dp/B0DN9NWL9H?th=1

• by having very large array of large radio antennas, long wave radio waves can be bounced off the ionosphere
• by bouncing down, they have the added advantage that they can detect low flying aircraft in valleys or relatively small distant boats
• eg. the Australian made Jindalee Operational Radar Network (JORN) system
  • transmits high frequency radio waves 110km up into the ionosphere and can detect objects 1000-3000km away
    • usually uses 5-30MHz frequencies which equates to 60 to 10m wavelengths
  • the radar's operations centre is at RAAF Base Edinburgh, north of Adelaide, and across the road is a vast DSTG site where researchers constantly tweaks the high frequency radio waves that give JORN its edge - the exact frequency within the 5–30 MHz band is chosen in real time based on the current ionospheric conditions to ensure reliable propagation and maximize coverage efficiency. Lower frequencies closer to 5MHz usually offer the best performance and reach, and are less affected by weather and environmental clutter.
  • JORN transmitter sites:
    • Laverton in Western Australia
      • 480 antennas consisting of two rows of poles sit side by side, stretching three kilometres
    • Harts Range, Alice Springs
    • Longreach in Queensland
  • can detect aircraft as small as 12m (eg. BAE Hawk 127) and boats as small as 56m (eg. Armidale-class patrol boat)
  • in response to issues with Trump, in April 2025, Canada announced plans last month to spend $6.5 billion to purchase JORN for its Arctic defence