Yagi antennas, which also go by the name of Yagi-Uda antennas, are named in honor of the 2 Japanese (engineers by profession) who invented them. We can find practical applications for these antennas in amateur radio, television reception, and as a bridge antenna that will help connect a site to a Wi-Fi base station.
The key radiating element of the Yagi type of antenna, otherwise known as the “oriented” part, is referred to as its “dipole”. In most situations, a “reflector” is positioned behind the driven part. The reflector usually adds 4 to 5 decibels to the signal.
Yagi and Their Advantages
We qualify Yagis as a directional type of antenna. Most of these antennas have a 50° to 70° beam diameter. Compared to omnidirectional antennas, they usually have a higher gain since they focus their data in just one direction only. This renders them very ideal for receiving weaker signals.
They also have a good range due to their high gain. Contrary to how antennas like log-periodic are built, Yagi antennas have the most gain with respect to their physical size.
Almost all signal noise from the opposite direction is filtered out by the antenna’s design. This explains the reason why Yagis make an excellent substitute for high-demand technologies such as telecommunications.
A Yagi type of antenna is easier to aim at than those of other arrays. But because of their design, they’re simple to mount even on vertical towers or any other form of structure.
Since Yagis are less challenging when placed alongside log-periodic antennas, they are generally less expensive. Even if printed circuit board Yagis are available, others can be produced with just a few well-placed rods.
Possible Disadvantages of Yagis
- The frequency range, or bandwidth, is somewhat restricted.
- The antenna would need to be very long if you are seriously aiming for a high gain level. Even then, if you have more than one Yagi in an array, the gain is reduced to only about 6-9 dB.
- By stepping further away from the frequency, the electrical properties of these types of antennas tend to wither away (feed point impedance, gain, front-to-back ratios).
- The main disadvantage of this type of antenna is that they are difficult to feed and match signals at higher frequencies.
Yagi antennas are designed for balance, but if a balun is used at the feed joint line where it links to the drive part, it runs the risk of becoming what it should not become, unbalanced.
They can be balanced or unbalanced, depending on the style of the driven feature. Remember that if relatively inexpensive Yagis are balanced, it takes away the need for a balun.
Adding elements to this type of antenna enhances its directionality. It broadens its attention, but since the signal-to-noise ratio is increased, it receives the signals from that direction way better than before. In summary, the levels of interference are significantly reduced, most notably from the sides.