Antenna length: When computing the optimal positions for the various elements it has been shown that in a multi-element Yagi array, the gain is generally proportional to the length of the array.The most critical element positions are the reflector and first director, as their spacing governs that of any other elements that may be added. one with a wide spacing between the elements gives more gain than one that is more compact. Element spacing: The spacing can have an impact on the Yagi gain, although not as much as the number of elements.For mid ranges of the number of directors, each director provides very roughly 1 dB of gain. Typically a reflector is the first element added in any Yagi design as this gives the most additional gain, often around 4 to 5 dB. Number of elements in the Yagi: The most obvious factor that affects the Yagi antenna gain is the number of elements in the antenna.There are several features of the design of a Yagi antenna that affect its gain: The gain of an antenna comes at a cost, and these have to be balanced against the advantages that coem from the additional gain. However, this may not always be the best option as there are several considerations. It is sometimes tempting to want to look for the maximum amount of forward gain in an antenna design. Therefore high gain and narrow beam-width sometimes have to be balanced to provide the optimum performance.

This means that very high gain antennas are very directive. Gain and beamwidth options for Yagi antenna As there is only a certain amount of power available, to create gain, power must be taken from one direction to put into the main beam. This can be reasoned by thinking of the available transmit power. If the Yagi gain increases, then the beamwidth decreases. There is a link between the gain and the beamwidth. There are many factors that affect the overall Yagi antenna gain. Using this it is possible to note that the gain of an antenna when compared to an isotropic source will be 2.1dB greater than that when it is compared to a dipole.įigures of antenna gain when compared to a dipole are often designated dBd, and over an isotropic source, they are designated as dBi. As the dipole has a directional pattern, it is possible to determine that the gain of a dipole is 2.1dB above that of the isotropic source in the direction of maximum radiation. This is an imaginary antenna that radiates equally in all three planes. The second type of antenna is called an isotropic source. The gain is the difference between the signals using the different antennas. The easiest one is to use a dipole, then real measurements can be made, first with the dipole and then with the Yagi. This means that the signal from the Yagi antenna has to be compared against a known standard. The gain is always a relative measurement. It is worth noting that the gain for receiving and transmitting are exactly the same. However it is necessary to understand a little about what the Yagi antenna gain is.īy focussing or 'beaming' any power that is transmitted from the antenna in the required direction, it means that the signal is stronger than it would have been without the gain of the antenna. One of the key factors about a Yagi antenna is that it provides gain. one with no active elements like transistors, etc) like the Yagi is equal for both transmit and receive, and therefore gain for transmitting will be the same as gain when receiving. It is worth understanding that the performance of a passive antenna (i.e. Yagi Uda antenna showing direction of maximum radiation The Yagi or Yagi-Uda antenna gain is particularly useful because it enables all the transmitted power to be directed into the area where it is required, or when used for reception, it enables the maximum signal to be received from the same area.Ĭoupled to this the fact that it has reduced gain in other directions means that it receives or transmits less signal in other directions thereby reducing the levels of interference. The gain is often the headline specification for the particular Yagi antenna. The key advantages for using a Yagi antenna are the gain and directivity it provides. Yagi antenna Yagi antenna theory & calculations Yagi antenna gain & directivity Yagi feed impedance & matching Yagi Antenna Gain, Directivity & Front to Back Ratio Yagi antenna gain is dependent upon many factors including the number of elements, spacing and several other minor factors.

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