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Tracking & Locating Devices Apple AirTags, Car Keys and more Source image: https://unsplash.com/photos/a-cell-phone-sitting-on-top-of-a-moss-covered-ground-ReQq6kUYjLI Modern technology has made it relatively easy to track the location of people or property for safety, security or other purposes. Trackers can be used to locate children, pets, your mobile phone, computer, baggage, products in transit, machinery, cars, boats, planes or just about any other movable object. By Dr David Maddison, VK3DSM T racking devices operate over various distances, from short to long ranges. Some can provide an absolute position fix, such as latitude and longitude coordinates, while others give a relative position, such as an approximate distance and direction from your current location. Modern GPS/GNSS receivers are small enough and have low enough power consumption to make them practical for use in portable devices. More recent technologies used for tracking include ‘multilateration’ (triangulation) with radio beams and ‘ultra-wideband’ (UWB) chips. This article will cover tracking 12 Silicon Chip techniques, technologies and methods and then give examples of common or interesting tracking devices. As mentioned in our June 2024 article on Privacy Phones (siliconchip.au/ Article/16280), it is generally possible for anyone carrying a mobile phone to be tracked even without their permission. Tracking techniques and technologies Satellite positioning systems, including GPS, Galileo, BeiDou and GLONASS, are collectively known as GNSS (global navigation satellite systems). Many trackers will locate Australia's electronics magazine themselves using GNSS and then transmit that location via WiFi, Bluetooth, 4G/5G or radio. Non-GNSS tracking devices typically emit a radio signal, either via Bluetooth, UWB or WiFi, which is then processed to extract positional data such as via one of the techniques described below: AoA, Multilateration, NFER, ToA, TdoA or ToF. One advantage of those systems is that they can work in places where GNSS signals are too weak or blocked, such as indoors or underground. Angle of arrival (AoA) The direction of a transmitter can siliconchip.com.au be determined by measuring the AoA of a radio signal using an antenna array and measuring the phase shift of a received signal between each of multiple antennas – see Fig.1. A second angle measurement from a second antenna array allows the location to be established at the intersection of the two directional vectors. Multilateration (see below) needs a minimum of three sensors, while this technique requires two. However, using more sensors generally provides better accuracy. Bluetooth This is a popular short-range wireless communications protocol for functions such as connecting wireless headsets to a phone or computer, connecting a phone to a car, printing, remote control etc. It has other applications, including locating and tracking objects. Its operating range extends to about 10m for basic Bluetooth and up to about 240m for Bluetooth 5.3 (depending on the amount of clutter). Bluetooth Low Energy (BLE) beacons are commonly used for tracking. One method of localisation for these beacons is multilateration, using three fixed beacons or ‘anchors’ to measure the distance to a movable device. Even with a single device, the distance can be roughly determined by measuring signal strength. A Bluetooth Distance Measurement API uses the Bluetooth RSSI (Received Signal Strength Indicator); the direction can be determined using antennas on multiple devices. Fig.1: the angle-of-arrival locating method using an antenna array, such as a WiFi router with multiple antennas. A second router is needed to establish the position (one just gives you an angle). Fig.2: the principle of multilateration using three fixed devices at the centre of circles with radiuses r1, r2 and r3; the tracked device is at the point (x,y). Multilateration This is also known as hyperbolic positioning or trilateration; it is the process of determining the position of an object by measuring the distance between three or more known locations and one unknown location – see Fig.2. The distance may be established by the time difference of arrival (TdoA) of radio signals, relative signal strength or other means. Near-field electromagnetic ranging Near-field electromagnetic ranging (NFER) is an emerging ranging technique not yet commonly used for tracking. A radio transmission’s ‘near field’ is the electromagnetic field close to the antenna (see Fig.3). Its properties differ from the electromagnetic field further away, the ‘far field’. Fig.3: radio transmissions differ in how they behave in ‘near fields’ (close to the transmitter) & ‘far fields’ (further away). Original author: Goran M Djuknic siliconchip.com.au Australia's electronics magazine August 2024  13 Close to a small antenna or emitter, in the near field, the electric (E) and magnetic (H) components of an electromagnetic (EM) wave are up to 90° out of phase. In the far field, the pattern of electromagnetic radiation is more conventional. The phase difference between the EM wave’s electric and magnetic field components in the far field is zero; they are in phase. Between those two extremes, the phase difference is less than 90°, so if the phase difference is measured, it can indicate distance. NFER uses frequencies below about 30MHz. As an example, for a 1MHz signal, Fig.4: the phase versus range relationships near an electric dipole. The phase angle (labelled “Phase Delta”) can be used to determine the distance in terms of wavelength. Original source: www.researchgate.net/publication/276919686 Fig.5: indoor WiFi positioning in an office environment using three routers with Received Signal Strength Indicators (RSSI). Original source: https:// github.com/sankalpchauhan-me/ IndoorPositioning Fig.6: how time-of-flight (ToF) is calculated in principle. δ is the delay in response from the target device, T_P is the signal propagation time, T_ACK is the time needed for acknowledgement and the ToF used in the calculated distance is T_MEASURED. Original source: https://w.wiki/AMEk 14 Silicon Chip Australia's electronics magazine the phase difference between the electric and magnetic field varies from 75° to 25° over the more linear region between 30m and 60m from the source (see Fig.4). With a delta of 50° over 30m, if the phase different were measured with a 1° accuracy, that would give a resolution of 1/50th of 30m, ie, around 60cm. NFER operates within about half a wavelength of the signal used. A 1MHz signal has a wavelength of 300m, so a range up to about 150m could be measured. NFER is suitable for indoor use where GPS signals can’t be received (for example). One disadvantage is that, due to the low frequencies required, efficient antennas are large. Possible solutions include fractal antennas, loop antennas or ferrite rod antennas (as used in small radios). US patent 2014/0062792A1 describes a way to use commercial AM broadcast signals as ‘signals of opportunity’ for NFER. Usually, they will be in the far field. Still, when such signals interact with structures like power lines, they can resonate within them, introducing near-field components as though that structure was an emitting antenna and enabling the signal to be used for NFER. For more on near fields and far fields, see these videos: ● “EEVblog #1273 - EMC Near Field vs Far Field Explained” (https://youtu. be/lYmfVMWbIHQ) ● “EEVblog #1178 - Build a $10 DIY EMC Probe” (https://youtu. be/2xy3Hm1_ZqI) ● “#234: Basics of Near Field RF Probes | E-Field & H-Field | How-to use” (https://youtu.be/ctynv2klT6Q) RSSI Fingerprinting Received Signal Strength Indicator (RSSI) Fingerprinting is a positioning method using WiFi where a database is created and constantly updated to record the locations and signal strengths of many WiFi access points from various known positions. This enables an unknown location to be quickly determined by comparing the WiFi signal strengths to signatures in the database, with a median accuracy of 0.6m. RSSI Multilateration Received Signal Strength Indicator Multilateration uses the relative strengths of signals as a proxy for the siliconchip.com.au distance between devices. An example of this method applied to WiFi routers is shown in Fig.5. Time of arrival (ToA) While not tracking techniques, ToA & TDoA (time difference of arrival) are used in other techniques described here. ToA is defined as the absolute time when a radio signal emanating from a transmitter reaches a remote receiver. TDoA is the difference between ToAs. Time of flight (ToF) Time of flight (ToF) is a WiFi-based position measurement technique, although the principle can be applied to other types of signals. It involves measuring the time taken for a radio signal to travel (at the speed of light) between a measuring station (in this case, a WiFi access point) and a target device (eg, a smartphone) – see Fig.6. The time taken to return is also measured, allowing for a delay due to response time. The distance between devices can be calculated, and in conjunction with the time taken to other measuring stations, the location can be determined. The system is accurate, but devices must be synchronised to a master clock. Ultra-wideband (UWB) UWB was briefly mentioned in our June 2024 article on Privacy Phones (siliconchip.au/Article/16280). This technology is incorporated into various devices, including some iPhones and certain Samsung and Google Pixel model phones (more on that later). UWB is a short-range radio protocol that operates between 3.1GHz and 10.4GHz. Radio energy is sent over a very wide bandwidth, around 500MHz or more, to allow the transmission of a relatively large amount of energy without exceeding regulatory limits for certain frequency bands or causing interference (see Fig.7). UWB utilises extremely short pulses of one or two nanoseconds. Positioning using UWB is capable of very high accuracy, with errors as little as 10-50cm or even down to centimetre-­level accuracy (see “Athlete trackers” below). UWB positioning or tracking systems ideally utilise three fixed receivers or anchors. Techniques such as ToA, ToF or TDoA are used to establish siliconchip.com.au Fig.7: the frequency range and spectral power density of UWB compared with other radio technologies. Source: www.rtsmartdata.com/technology/uwb Fig.8: one variation of the Pulse Position Modulation (PPM) scheme used in UWB communications. Source: www.rescueswag.com.au/products/rescueme-plb1 the distance between the UWB tag or device and the receivers; the position of the receiver is then established by multilateration. Unlike conventional radio, in which information is transmitted via variations in frequency, phase or power, with UWB, information is encoded as pulses with specific time shifts in a scheme known as Pulse Position Modulation (PPM) – see Fig.8. UWB can transmit data at a high rate (~100Mbit/s), with transmissions over 1Gbit/s having been demonstrated. UWB is relatively energy-efficient compared to other methods, and signals can pass through many obstacles, including certain types of walls and people in crowds. Information sent from a UWB device Australia's electronics magazine usually contains its ID, ToF and timestamp data. UWB is governed by the IEEE 802.15.4a/z standard. UWB chips are fitted to the following devices: • the Apple iPhone 11 and later, excluding the iPhone SE (2nd and 3rd generation) • the Apple Watch Series 6 and later • some other Apple devices • various Samsung Galaxy models (including the Galaxy Buds Pro 2) • the Google Pixel 8 (and some other phones from Google) • the Xiaomi MIX4 • the Motorola Edge 50 Some devices, such as the iPhones with UWB, always have power to the UWB chip even when the phone is ‘off’ so it can be used to find them. August 2024  15 Wireless LAN (local area network) WLAN/WiFi can be used for location and tracking. Google uses publicly broadcast data from WiFi routers that have been scanned as they drive around in their Street View vehicles. Their locations are recorded (siliconchip.au/link/ ab9n) to enhance the accuracy and speed of location in conjunction with GPS (or to provide location even without GPS). This is used by any tracking app or hardware that uses Google Location Services. In smaller areas with access to a WiFi network, devices can be located using techniques such as RSSI Multilateration, RSSI Fingerprinting, ToF and AoA. Examples of tracking devices Here are some example of commonly found tracking devices, listed in alphabetical order. Note that this is not meant to be a comprehensive list. Aircraft tracking Commercial and many other aircraft are routinely tracked via a variety of methods, including Aircraft Communications Addressing and Reporting System (ACARS), Automatic Dependent Surveillance–Broadcast (ADSB) and FANS (Future Air Navigation System). ACARS communicates aircraft events, including equipment and sensor status, via VHF and ground stations when near land (line-of-sight, within about 370km) or via satellite receivers for almost global coverage. ACARS does not usually send position coordinates but does send speed and altitude. ADS-B broadcasts an aircraft’s callsign, position, altitude, velocity and other data twice per second. That information is sent to air traffic controllers via ground stations or satellites. Positional information is obtained via GNSS. Air Services Australia operates 61 ground stations for ADS-B. ADS-B is mandatory in Australia for aircraft flying under instrument flight rules (IFR); other countries have similar rules. FANS is a system that provides a data link between an aircraft and aircraft traffic controllers, including information concerning air traffic control clearances, pilot requests and position reporting. Communication is via ground stations or satellite. In 1995, a Qantas Boeing 747-400 (VH-OJQ) became the first aircraft to use the Rolls-Royce FANS-1 package, and Air New Zealand soon followed with a package from General Electric. Ankle bracelets Courts order police to fit some criminals or suspects with a GPS ankle (or wrist) bracelet for tracking them. These can be used to restrict them to a particular zone (such as a home) or prevent them from entering designated prohibited areas (such as where a victim might live or work, airports, schools, shopping centres etc). Alerts for violations are issued via the mobile phone network. These devices are waterproof, are designed to detect tampering and will periodically ‘check in’, generating an Fig.9: internal and external views of an ElmoTech TRXL-830 ankle monitor. Source: https://fccid.io/LSQ-TRXL-830/Internal-Photos/InternalPhotos-1338485.pdf 16 Silicon Chip Australia's electronics magazine alert if they are not functioning. As the ankle monitor is offered as a ‘service’ to the recipient to allow some freedom of movement, tampering is regarded as a very serious matter and will likely result in them being sent to jail instead of having a small amount of freedom. Similar tracking devices can also be used for people with mental impairments (eg, dementia) who may wander away from institutional care facilities. These devices can determine their location via GPS, LBS (location-based service, using mobile phone towers) or indoor beacons using BLE when no GPS or LBS signal is available. One example is the ElmoTech TRXL-830 (see Fig.9), designed to enforce curfews. It has a receiver unit that logs the presence or absence of a ‘client’ wearing one of these devices and compares that with a stored schedule of curfew hours the person has to conform to. If they are not present, the receiver unit reports the violation. Bracelets with alcohol monitoring The SCRAM Continuous Alcohol Monitoring (CAM) bracelet (Fig.10; siliconchip.au/link/abwj) is for certain classes of criminals, such as habitual drunk drivers or domestic violence offenders. It samples the wearer’s sweat for alcohol every 30 minutes and reports the result. Alcohol in sweat is detected with an electrochemical fuel cell. The bracelet must be worn in contact with the skin. The SCRAM CAM does not include tracking but can be used in conjunction Fig.10: the SCRAM Continuous Alcohol Monitoring (CAM) bracelet detects the wearer’s blood alcohol level via their sweat. Source: https://go.scramsystems. com/l/149911/2016-05-02/ tmlc/149911/1614372926rk0W3lb1/ scram_cam_product_brochure.pdf siliconchip.com.au with a tracking bracelet on the other ankle. Apple’s AirTag T h e A i r Ta g (shown here and in Fig.11) is a small disc-like token designed to find and track keys, luggage, computers, cars and any other object they are attached to, including people. AirTags use the proprietary Apple “Find My” network, a crowdsourced mesh network that uses an estimated one billion Apple devices. It requires an iCloud account and uses both Bluetooth and ultra-wideband (UWB) technology. The AirTag transmits a Bluetooth ‘beacon signal’ that is anonymously received and retransmitted by other Apple devices without alerting the other device’s owner. iPhone 11 or later users can also utilise the phone’s U1 UWB chip (or U2 in the iPhone 15 and later) to locate the AirTag more precisely. The U1 has an approximate range of 20m, while the U2 has a range of up to 60m, although estimates vary and it depends on conditions. Some reports claim AirTags can be detected at up to 250m outdoors. Despite the relatively short ranges, you or your AirTag are never likely to be far from an iPhone in an urban area. Some people have mailed packages with AirTags to follow their route and have had numerous ‘pings’ at airports, warehouses and similar facilities. Details on the impressive internals Fig.13: a Playertek GPS device weighing 42g (top right) with a screen showing the Playertek athlete monitoring tracker software. It depicts various parameters and a heat map to show the location of athletes on the field. Source: https:// performbetter.co.uk/products/playertek of the AirTag can be seen at https:// adamcatley.com/AirTag Athlete trackers Athletes’ activities can be monitored by GPS or UWB (ultra-wideband) tracking devices worn within their clothing, with the goal of improving performance. The Playertek (Fig.13) is an example of an athlete tracker that uses GPS. In the USA, the National Football League (NFL) uses UWB trackers from Zebra Technologies (www.zebra.com) to monitor athletes and the ball. The data collected includes the ball altitude, velocity, rotation, player speed, passing rates, rushing attempt in yards, pass completion, receiver separation and more. They call this “Next Gen Fig.11: the internals of an Apple AirTag (both sides). Onboard devices include the Bosch Sensortec BMA28x 3-axis accelerometer, Apple U1 ultra-wideband transceiver, Nordic Semiconductor nRF52832 Bluetooth low-energy SoC w/NFC controller and various memory, audio and power supply components. Source: www.ifixit.com/News/50145/airtag-teardown-part-one-yeah-this-tracks (CC-BY-NC-SA) siliconchip.com.au Australia's electronics magazine Stats”; see https://nextgenstats.nfl. com/glossary Each NFL stadium has 20-30 UWB receivers, two or three trackers in each player’s shoulder pads (to ensure better tracking when close to the ground), trackers on officials and other items. They collect around 1000 data points per second with centimetre accuracy. A total of around 250 trackers are used for each game. A game can be replayed in animated form in various apps using the data (see siliconchip. au/link/abx1). Boats Trackers for boats use the mobile phone network or NB-IoT networks close to shore, or a satellite service if further out to sea (see Fig.12). Some Fig.12: the Keep Track G120 Cellular and Satellite GPS Tracker showing the optional Iridium satellite module. It can be used to track other assets apart from boats. Source: Keep Track GPS – siliconchip.au/link/abx2 August 2024  17 use both mobile and satellite links. NB-IoT stands for ‘narrowband Internet of Things’ and is part of the mobile network. Telstra’s NB-IoT coverage is shown at siliconchip.au/link/abwk Child trackers Various child-tracking devices are available. These are similar to devices used for tracking adults but with the style and functions tailored for children and their carers. The Jiobit (www.jiobit.com) is a highly-rated pendant-type device for tracking children, but it is not supported in Australia. There are many watch-style devices, some of which are also suitable for adults. For example, the Apple Watch SE is not designed to track children but can be set up for such use. Two other examples (of many) include the Kids Buddy Watch (see siliconchip.au/link/abwl) and the Garmin Bounce (siliconchip.au/link/ abwm) – see Fig.14. JB HiFi sells a range of these devices, as shown at siliconchip.au/link/abwn Cube Shadow The Cube Shadow (https:// cubetracker.com/) is a subscription GPS tracker device and service that connects via the mobile phone network. It is advertised for tracking vehicles, assets, fleets, the elderly and pets. Although it is advertised as a global service, the website states, “We currently do not offer shipping outside the USA”. Chipolo ONE Spot and CARD Spot These AirTag alternatives work with Google Find My Device (see Fig.15), although they do not support UWB. See siliconchip.au/link/abwo Digital Car Keys This type of virtual car key is powered by a smartphone or watch (Fig.16). While not a tracker, it uses similar technologies, including UWB. The The misuse of trackers and the Tracker Detect app Unfortunately, criminals have been known to use tracking devices to stalk, harass and track victims. Apart from the Tracker Detect app, there is no universal or practical way to detect or disable them. Blocking GPS or phone signals is illegal, so if you think you are being stalked, contact your local police. Apple AirTags have been alleged to be misused in this way, although no doubt others have been too. If you have an Apple device with iOS 14.5 or later, it will alert you to the presence of an AirTag that is not yours and is moving with you. For further details on that, see siliconchip.au/ link/abwv You can detect the presence of Apple AirTags using an Android phone by using a free Apple app called Tracker Detect. If an AirTag has been tracking you for more than ten minutes, the App will allow you to play a sound on the AirTag to help you find it. Android versions since v6.0 (basically any modern version) can also provide alerts for unknown trackers; see siliconchip.au/link/ abww What about GPS trackers that transmit location data via the mobile An unknown tracker alert from a phone network? Presumably, devices recent version of Android. Source: that detect mobile phone activity can https://support.google.com/android/ detect such trackers. We came across answer/13658562?hl=en two covert mobile detector devices: the PocketHound (siliconchip.au/link/ abwx) and the WG Portable Mobile Phone Detector (siliconchip.au/link/abwy). If an active tracker does not use the mobile network, it would be difficult to detect, especially if the radio link uses spread spectrum techniques or extremely low power transmission like LoRa. For further information, see the article at siliconchip.au/link/abwz and the video titled “How Apple AirTags are being used by criminals” at https://youtu. be/OfXyRUwvQ8Q 18 Silicon Chip Australia's electronics magazine Fig.14: a Garmin Bounce tracking watch for children, with a screen showing the child’s location. Source: www.garmin.com/en-AU/ p/714945#overview Fig.15: a Chipolo ONE point tracking device in use. We would keep the tag inside the suitcase rather than on the outside (as long as the case is not metallic). Source: https://chipolo.net/ en/products/chipolo-one-point siliconchip.com.au Car Connectivity Consortium (CCC) maintains the specification. Car manufacturers who support the standard include AITO, BMW, BYD, Genesis, Gogoro, Hyundai, Kia, Lotus, Mercedes Benz, MINI, RAM, Škoda & Volvo. The keys are stored in mobile digital wallets such as Google Wallet, Samsung Wallet, Huawei Wallet and Apple Wallet for iOS and watchOS. Communication occurs via NFC (near-field communication) at very short ranges or UWB at longer ranges. Emergency locator transmitter (ELT) ELTs signal aircraft distress. They operate similarly to EPIRBs and transmit on 406MHz and 121.5MHz. Emergency position-indicating radiobeacon (EPIRB) An EPIRB (Fig.17) is used by boats or ships to communicate a request for immediate assistance, for example, if the vessel is sinking or there is a medical emergency. The device sends a 406MHz distress signal to a Cospas-Sarsat satellite (www.cospas-sarsat.int/en/), which then reports the position indicated by the EPIRB device (obtained via GPS or other satellite navigation system). It then reports the emergency to appropriate search and rescue (SAR) authorities for that area. If a position was not transmitted, it calculates the approximate position by analysing the signal. When SAR are close to the reported position, they can home Fig.16: opening a Kia car with a digital key via UWB. Source: www.kia.com/mu/owners/ owner-resources/quick-tips/ connectivity/setting-kia-digitalkey2-touch-smartphone.html in using radio direction finding with the EPIRB’s 121.5MHz homing signal, strobe lights on the device or the AIS (automatic identification signal) on newer devices. An EPIRB is activated either by contact with water or by manual activation; many are activated automatically and ‘float free’ if a vessel sinks. If using one of these devices, note that it is a free service but it is essential to register it correctly. They are mandatory in certain jurisdictions for certain types of vessels, but in any case, they are recommended for whatever vessel you use. Note that 121.5MHz is no longer monitored by satellites (as with older EPIRBs), but it is still used for homing purposes and is also the International Air Distress frequency. Google Find My Device This relatively new network will Fig.17: a typical EPIRB; this one is a GME MT600G. Source: www.gme.net.au/au/ emergency-safety/mt600g Fig.18: an example of items tracked using Google’s Find My Device network and an Android phone. Source: https://blog.google/ products/android/androidfind-my-device siliconchip.com.au Australia's electronics magazine work with all Android devices (about three billion of them) – see Fig.18. It is intended to be equivalent to Apple’s “Find My” network. Until recently, only Apple users have enjoyed the ability to utilise a huge number of devices that form a mesh network to find an AirTag. Now that ability has come to Android devices (running Android version 9 ‘Pie’ or later) via an upgraded Google Find My Device network, which started to be rolled out worldwide on April 9th this year – see siliconchip. au/link/abwp The rollout appears to have reached Australia in late May/early June. Like the Apple Find My network, the Google/Android Find My Device network utilises a vast network of Android devices as part of a crowd-sourced mesh network to communicate the encrypted location of a tracked device without needing the knowledge or permission of the other Android users. As with Apple, the connection is made to the mesh network via Bluetooth. Google says that all communications via the Find My Device network are end-to-end encrypted, and the location of devices participating in communicating data via the mesh network is not known to Google or anyone else. There are said to be numerous privacy safeguards. Security alerts will be provided to users if any unwanted Find My (iOS) or Find My Device (Android) compatible tags are tracking them. Like late-model Apple iPhones, Google Pixel 8 and 8 Pro phones can be tracked even if they are ‘off’ due to the ultra-wideband chip being constantly powered. August 2024  19 Is it possible to defeat GPS trackers? Sadly, criminals can detect and defeat GPS trackers attached to protected equipment. Methods used include GPS jammers, scanning for RF emissions, visual inspection, blocking devices (such as wrapping them in aluminium foil), physical removal or destruction of trackers and the use of a GPS signal spoofer to make the device appear to be in a different location than it really is. The HHD S7 tracker (siliconchip.au/link/abx0) is an example of an assettracking device that is said to be detection and jammer resistant. The device is sold as a subscription rather than a one-time purchase. Third-party trackers designed for the Find My Device network include Chipolo and Pebblebee, with devices yet to be released from Eufy, Jio and Motorola. Find My Device seems not to work on a locked-down privacy phone, as enabling it would defeat many of the privacy functions of such a phone. However, some options and apps are discussed for the privacy-focused GrapheneOS at siliconchip.au/link/ abwq Mobile personal alarms Elderly people typically use these devices, which generally are in the form of a pendant or wristband with a ‘panic button’. One model we are familiar with is the LiveLife Mobile Alarm (https://livelifealarms.com.au) shown in Fig.19. When the button is pressed, it calls a series of nominated contacts, sends the user’s location via text message and establishes hands-free two-way voice communications. It will also detect calls and issue an alert. The location is established via GPS, WiFi and Google Maps, with communications via the Telstra 4GX mobile network. 4GX is a Telstra marketing term for the 4G 700MHz (Band 28) network, which works at longer ranges than other parts of the 4G spectrum. Periodic testing of such life-­saving devices is highly recommended. Another similar product we saw was the Adult Buddy Watch (siliconchip. au/link/abwr) – see Fig.20. Mobile phone tracking apps You can install these apps on your phone and those of willing friends and family members, including children, to enable you to see where they are. Such apps include: • Familo (available on Android and iOS) – www.familo.net/en/ • Family Locator (Android and iOS) – https://family-locator.com • Find My (iOS) – www.apple.com/ au/icloud/find-my • iSharing (Android and iOS) – https://isharingsoft.com • Life360 (Android and iOS) – www.life360.com/au/ Pebblebee These Bluetooth trackers will soon be offered in versions for both iOS and Android. The Android version supports Google’s Find My Device network. They do not use UWB. Pet RFID implants These RFID devices are about the size of a large grain of rice and are used to identify a pet (eg, if they are lost). Some have considered whether such a device can be used to track an animal, but it is very short range only and can’t be sensed more than about 10cm away. Pet finders These use various tracking methods. For short ranges, up to 100m or so, Bluetooth or WiFi can be used to track a pet. The location might be provided as a range with no specific location or, if the tracker is equipped with GPS, a location if a GPS signal is available. For longer ranges, a tracker con- Personal locator beacons (PLBs) PLBs are similar to EPIRBs but are intended for land-based use, such as by bushwalkers and outback adventurers – see Fig.21. They are typically smaller than EPIRBs and don’t usually have strobe lights or water activation. If you intend to use one, make sure it’s registered correctly. Fig.19: a LiveLife mobile personal alarm. Source: https://livelifealarms. com.au/product/order4GX-mobile-alarm Fig.20: the “Adult Buddy Watch” from Buddy Gard. Source: https:// mybuddygard.com.au/ pages/adult-buddy 20 Silicon Chip nected to a mobile phone network can transmit GPS coordinates provided there is network coverage. Devices that connect to the mobile phone network typically require a subscription to function. When phone network coverage is unavailable, there is also the Aorkuler dog GPS tracker (https://aorkuler. com). It has its own radio transmitter and receiver rather than using a mobile phone, transmitting a GPS location to the receiver up to 5.6km away, depending on terrain, according to the manufacturer. We could not find out what frequency or certification it uses, so we are uncertain if this device would be legal to use in Australia or New Zealand. Some trackers enable ‘geofenced’ boundaries to be established, so an alert is issued if a pet wanders outside those boundaries. Pet trackers, like others, require regular battery replacement or recharging, as they can use a reasonable amount of power. They typically need to be charged every few days. Australia's electronics magazine Fig.21: a miniature PLB (emergency beacon) suitable for bushwalkers. This is the RescueME PLB1; it weighs 65g. Source: www. rescueswag.com. au/products/ rescueme-plb1 siliconchip.com.au Q-TRACK Q-TRACK produced a range of devices using near-field electromagnetic ranging (NFER). The company has since been acquired by GaN Corporation, and the products appear to no longer be available. NFER is an emerging technology. Radio-based key finders These are always listening for a signal from a dedicated transmitter and will sound if the transmitter is activated. One example is the “REDPINGUO Wireless RF Item Locator”. The range is said to be about 30-40m and it operates at 433.92MHz. Fleet vehicle trackers Rental cars, other rented assets and vehicle fleets are often tracked by GNSS-based devices to ensure they are used according to usage agreements, to prevent theft and for general management purposes. Highly-valued private cars may use these devices. Netstar (www.netstaraustralia.com. au) is an example of an Australian company that advertises its products and services for such devices. Radio Frequency ID (RFID) RFID tags are attached to objects to identify them or track their location, such as the progress of an item down an assembly line or through a delivery network like a postal service. RFID tags may be passive or active. Short-range passive tags contain circuitry that is activated by energy from an interrogating radio beam, while active tags contain a battery and work at much longer ranges. Cited ranges for readability of the tags vary considerably according to the model and technology used. Still, typical figures quote up to 1m for a passive tag at 13.56MHz, up to 100m or more for an active tag operating at 433MHz or 2.45GHz and 200m or Fig.24: the Lars Thrane LT-3100S GMDSS (Global Maritime Distress and Safety System) for SSAS and other forms of ship-to-shore voice and data communications via the Iridium satellite system. Source: www.prnewswire. com/news-releases/new-era-for-safety-at-sea-as-first-ever-iridium-gmdssterminal-is-unveiled-300861105.html higher in other frequency bands. Common examples of RFID devices are pet ID implants, inventory tags in stores, access control devices, trackers for railway rolling stock, trackers for shipping containers, some passports (including Australia’s), books in some libraries, toll collection devices and many others. The devices are generally very cheap. We published a DIY RFID tag design in the July 2023 issue (siliconchip.au/ Article/15860). Samsung SmartTag2 The SmartTag2 (Fig.22) uses Bluetooth and UWB for tracking and has a range of up to 120m from the nearest phone. It does not support Google’s Find My Device network and only works with Samsung Galaxy devices. Nevertheless, it has received favourable reviews, such as siliconchip.au/ link/abws It has a claimed battery life of 500 days, or 700 days in power-saving mode. Shipping container tracking Shipping containers are tracked using various technologies and sensors, such as GPS with connectivity provided by Bluetooth, LPWAN (Low Power Wide Area Network), mobile IoT and satellite. Some also include door and movement sensors, temperature sensors and weight sensors. One example is the Vimel VIM4GCONT (Fig.23). It has a five-year battery life with daily location updates, stores location data if out of network coverage and more (see siliconchip. au/link/abx3). Ship security alert system (SSAS) The SSAS alerts authorities that a ship is under attack by pirates or terrorists – see Fig.24. An SSAS report contains the ship name, unique identification numbers like MMSI (Maritime Mobile Service Identity), IMO (International Maritime Organisation) number and call sign, the date and time, the ship’s current position, speed and course. Fig.23: the Vimel VIM-4GCONT is a shipping container tracker. Source: Security Lab – siliconchip.au/link/ abx3 Fig.22: typical use cases for a Samsung SmartTag2. Source: www.samsung. com/au/mobile-accessories/galaxy-smarttag2-black-ei-t5600bbegau siliconchip.com.au Australia's electronics magazine August 2024  21 Figs.25 & 26: the mOOvement GPS ear tag (www.moovement.com.au) for domestic cattle (left). This model has a long battery life due to onboard solar cells for charging. As one use example, data from the device can be used to create a heat map of grazing patterns (right). Sound-based devices Examples of these devices are early key finders that require you to whistle or clap your hands to activate a tone. You could then ‘home in’ on the tone using your ears. However, they were generally unreliable and are now largely obsolete. Tile Tile trackers (www.tile.com/en-au) are Bluetooth-based tracking devices for keys, wallets, luggage and other objects. If a tagged item is lost, a smartphone app can make the Tile device make a noise, and the last known location will be shown on a map. A lost phone can also be made to make a sound by double-clicking on a Tile tracker. orbit at 850km altitude, orbiting about every 100 minutes. A message length of 3-31 bytes is allowed per satellite pass. From there, data is transmitted to a ground station. Wildlife is also tracked using mobile telephone networks. When the animal is out of range, tracking data can be cached. VHF, UHF or LoRa can be used for shorter-range communications. There is a free worldwide animal tracking database where researchers, journalists, students or developers can access animal tracking data. It is called Movebank (siliconchip.au/ link/abwt). There is a free app for members of the public to track various animals; see siliconchip.au/link/abwu and the YouTube video titled “Animal Tracker App” which you can view at: https:// SC youtu.be/wdG99OdwpWE Animal tracking Depending on the species, wildlife and farm animals can be tracked with GPS tags or collars. For domestic livestock such as cows, a GPS ear tag can be attached (see Figs.25 & 26). In that example, GPS location data from the tag is relayed via a low-cost LoRaWAN (Long Range Wide Area Network) network on the farmer’s property, with a range of about 8km. For more information on LoRa, see page 21 of our Digital Radio Modes article from May 2021 (siliconchip.au/ Article/14848). In the case of wildlife that travels a long distance, tracking can be performed via the Argos satellite system (www.argos-system.org) with its uplink at 401.65MHz (see Fig.27). This system has seven satellites in polar 22 Silicon Chip Fig.27: a wild animal (a female elk) with a North Star GPS tracking collar. Source: www.northstarst.com/tracking-wildlife/wild-animals Advice for tracking pets If you use a tracker for your pet, you should familiarise yourself with its operation, capabilities and limitations before it is needed. That includes replacing or charging the battery when necessary. I know of someone who did not do this, and when their pet wandered off, the device (which they had never tested) did not work! Fortunately, the pet was found the old-fashioned way, with a person who found it calling the phone number on the collar. Australia's electronics magazine siliconchip.com.au