How far will 25mw get you?

This is a Taggle Systems device, a low-power radio transmitter that can send data from water meters to a network of receivers. It operates at 25 milliwatts, or 0.025 watts, which is a very small amount of power compared to other wireless devices. It is usually attached to a water meter and placed close to the ground, sometimes even under the soil or inside a pit. This makes it hard to see and protects it from harsh weather conditions. However, it also means that it faces more obstacles and interference when transmitting its signal.

The Taggle Systems Byron device operates on a frequency of 922 MHz, which is allocated for industrial, scientific, and medical (ISM) applications in Australia. It uses a simple dipole antenna that radiates equally in all directions. The antenna is attached to the device’s circuit board, which contains a micro-controller, a RF transmitter, a battery, and a sensor interface.

The device only transmits once per hour, which helps to conserve its battery life and reduce its environmental impact. The battery can last for more than 10 years, and its usage is predictable because the device has a fixed transmission schedule and power consumption. This makes it easy to plan for maintenance and replacement of the device.

The device can be configured to transmit data at different intervals, depending on the application.

The data transmitted by the Taggle device consists of a unique identification number, a sensor reading, and a battery voltage. The data is encoded using a proprietary protocol that ensures reliability and security. The data is sent as a short burst of RF signals that lasts less than a second. The RF signals are modulated using frequency shift keying (FSK), which means that the frequency of the signal changes according to the binary data. The RF signals have a bandwidth of 25 kHz and a power of 25 mW.

The Taggle device can communicate with a receiver that is located anywhere within its range. The range depends on several factors, such as the height of the transmitter and the receiver antennas, the terrain, the weather, and the presence of obstacles or interference. The Taggle device’s datasheet provides some estimates of the range for different scenarios. For urban environments, where there are many buildings and other sources of RF noise, the range is between 2 and 5 km. For rural environments, where there are fewer obstacles and less interference, the range is between 5 and 30 km.

However, these estimates are not absolute, and there are cases where the Taggle device can achieve much longer ranges. One such case is when the receiver antenna is located on a high elevation, such as a hill or a tower. This gives the receiver antenna a clear line of sight to the transmitter antenna, which reduces the attenuation and reflection of the RF signals. In addition, the higher elevation also increases the effective area of the receiver antenna, which improves its sensitivity and ability to capture weak signals.

An example of this case is when the Taggle device is installed on a water meter that is located at ground level in a rural area. The water meter is surrounded by vegetation and sometimes buried under soil or debris. The Taggle device transmits data once per hour, which consumes very little power from its battery and provides a very predictable battery life. The receiver antenna is mounted on a mast that is 6 meters tall. However, the mast is also situated on top of a hill that is 596 meters above sea level. This gives the receiver antenna an advantage of more than 600 meters over the transmitter antenna.

As a result, the receiver antenna can receive the data from the Taggle device even though it is 96 km away from it. This means that the device has achieved a range that is more than 19 times higher than its datasheet’s maximum estimate for rural environments.

What I find more impressive is that we are hearing this tag at -133.75 dB in an area that has a noise floor of -120dB. so we are decoding a signal 13db below the noise floor.

This demonstrates the impressive performance and versatility of the Taggle Systems device and its RF technology.