VSWRĪs can be seen from the table, VSWR of 2 corresponds to 11.1% of reflected power. In general, if the VSWR is under 2 the antenna match is considered very good and little would be gained by impedance matching. In this case, no power is reflected from the antenna, which is ideal. The smaller the VSWR is, the better the antenna is matched to the transmission line and the more power is delivered to the antenna. The VSWR is always a real and positive number for antennas. The reflection coefficient is known as s11 or return loss. It is a function of the reflection coefficient, which describes the power reflected back from the antenna. VSWR stands for Voltage Standing Wave Ratio. These are the most commonly used and heard terms when doing antenna tuning. It can increase the working range and can also help in reducing the power consumption of wireless device. A properly tuned antenna can help in many ways. Why tune an antenna?Īntenna is probably the most important part of a wireless system, as it is responsible for sending and receiving the data on the physical layer. If the antenna already has an impedance equal to the source impedance, there is no need of tuning. Antenna tuning is basically, the process of matching the antenna impedance with source impedance. The antenna) should be equal to the source impedance(usually 50 ohm or otherwise described). To reduce these reflections and ultimately power loss, the load impedance(i.e. These reflected waves creates ‘ Standing Waves’ in the transmission line and results in losses. Minimum reflection is obtained when source impedance is equal to the load impedance. When a high frequency signal is fed to an antenna to radiate, not all the power is radiated by the antenna but a small portion of it is reflected back to the source. These are determined by antenna's physical properties which include the shape, size, material and also by the environment. What is antenna tuning?Īn antenna has a resistance, capacitance and inductance. Additional extension cables are available as required.Heard about antenna tuning but couldn't get past the mathematics behind it? Here is a quick and practical guide on how to go along with antenna tuning for your own IoT device. The cable is a composite design incorporating coaxial, power supply and control cables. This comprises of a 1.5-meter stub cable with a 4.5-meter extension cable for connection to the transceiver. The 911 is supplied complete with fully terminated control cables having an overall length of 6 meters. If any significant variation occurs the 911 will re-tune the antenna automatically. Following initial tuning, the antennas VSWR is monitored. On any subsequent use of that frequency, the 911 reconfigures to the stored settings in typically 25 milliseconds. The 911 tuner features a memory facility that stores the configuration required to tune to a frequency. Tuning is rapid, typically less than two seconds the first time RF is applied, either whilst the operator is talking or when the “Tune” control is activated on the transceiver. Housed in a fully weatherproof enclosure the 911 will tune long wire antennas, wire loop antennas or whip antennas over a frequency range of 2 to 30MHz.
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