A Yagi antenna, also known as a Yagi-Uda antenna, is qualified as a directional type of antenna. This means to say that the signal it will emit will only go in one direction. It is composed of a long transmission line and a single driven element composed of two rods that are linked on either side of the transmission line.
The parasitic yagi type of antenna elements work by re-radiating their transmissions in a phase that is marginally higher or distinct from the driven unit. This encourages the transmission to be strengthened in one or more directions while being reversed in others.
Because the yagi elements are not particularly driven but rather pick up the power of the driven element, they will be alluded to as parasitic elements since they function as additional elements.
If we are to look for at least one design fault in the way yagi type of antennas are built, it will have to be the power in which these additional elements are not directly powered up.
As a consequence of which, it seems we can use it to have significant control over the induced current phase and amplitude. This is commensurate with the length and distance between it and the dipole or the part that is driven.
So, what is all this trying to convey to us?
This is demonstrating to us that trying to obtain complete but another cancellation direction may not be entirely feasible. Even so, it is possible to obtain a maximum reinforcement rate through one direction; it may ultimately lead you to a high level of gain.
What the Yagi type of antenna presents us is not just useful and relevant gain levels but is also reputed because it delivers front-to-back ratios.
The beamwidth for this type of antenna would be ranging anywhere from 50° to 70°. And, since they are commonly focused in just one direction only, they have a high gain correlated with antennas with omnidirectional properties. This is the reason why they are perfect to take advantage of when you are receiving rather weaker signals.
The high gain of the Yagi system of antennas is what gives them their well-known range. The Yagi system of antennas are popular and in high demand because of their good range, and it would not have been possible if not for its high gain capability. They have the most gain in comparison to other kinds of antennas, including the log periodic.
Yagi antennas are far easier to aim for. Design and structure-wise, they are much easier to mount on horizontal towers or whichever form of structure you need to have them on.
They are normally less expensive when placed alongside log-periodic antennas because they come in an easier, less complex assembly process. While the Yagi circuit printed board is easily obtainable, you can come up with your own by making use of properly positioned rods.
By putting on additional elements to a Yagi antenna, what you are doing is further enhance its level of directionality. Its focus may narrow, but it does not stop it from receiving signals coming from that direction. One good thing about it is that it is made better than before which is made possible by the massive spike in the signal to ratio.
Simply put, you have reduced the levels of intrusion, particularly those coming from the sides.
By stepping further away from the range of the Yagi frequency, you will render the electrical characteristics of the antenna to degrade. The underlying reason for that is that this type of antenna is primarily designed with resonant components, adding reactance consequently making the SWR spike.