Different types of antennas function differently based on the radiation pattern, features, and frequency range. Log An antenna having several dipoles of varying lengths and spacing is called a periodic antenna. Although they each have minor variances, they may seem to be Yagi antennas.

1. Advantages and Disadvantages of Log Periodic Dipole Antennas
Antennas are of different kinds and work differently according to the radiation
pattern, characteristics, and frequency range. Log Periodic antenna is a type of
antenna that contains multiple dipoles with various lengths and spaces. It might
look like a Yagi antenna but both of them have some differences.
In a log periodic antenna, the dipole elements reduce in size and have different
lengths. In this blog, we will discuss the Advantages and Disadvantages of Log
Periodic Dipole Antennas in detail with other things.
Construction of Log periodic antenna
LPDA or log periodic antenna is constructed by using the different half-wave
dipole elements with increasing length. It is designed in such a way that the
electrical properties will show periodic repetition with frequency logarithm.
In this antenna, the different dipoles of various lengths and spacing are put
together. External excitation in an LPDA is given by using the balanced
transmission line. This line is exchanged between the different terminals of the
dipole.
The structure of a log Periodic antenna is somewhat similar to the Yagi-Uda
Antenna containing a half-wave dipole antenna. The different elements of an
LPDA are mounted on one line with the help of a support boom. Both these
elements operate differently. Adding elements in a log periodic antenna will
increase its frequency response or bandwidth.
Advantages of a log periodic antenna
After discussing the definition and construction of an LPDA, we will now look at
the major advantages of this antenna. Some of the major benefits of an LPDA are:
1. Wide bandwidths
One of the major Benefits of Log Periodic Dipole Antennas is the wide
bandwidths. These antennas have broader bandwidths than Yagi antennas and
work on HF as well as UHF frequencies. Apart from that, the log periodic antennas
are also used for EMC measurements when one needs to scan a wide range of

2. frequencies. These antennas have a similar radiation resistance over their range
of frequency
2. Ratio and gain
Log periodic antenna has the same gain and back-to-front ratio with a high
forward gain. A gain of 3 to 6 dB gain over a 2:1 bandwidth works in the case of a
log periodic antenna. The feed point impedance in an LPDA is constant.
3. Simple to use
Using an LPDA is very easy as it contains dipole elements of different lengths. Due
to its simple design, it is very comfortable to use a log periodic antenna. You can
also make various changes in an LPDA due to a simple design. Besides, the
changes also leave a very small impact on the electrical characteristics.
4. Low SWR
LPDA has a low SWR and it is possible to achieve an SWR level in a log periodic
antenna. Using a single LPDA can easily replace multiple Yagi antennas as it acts
mostly like Yagi antennas.
5. Multiple applications
You can use a log periodic antenna for various tasks and applications such as
HF/UHF/VHF communication and TV reception. It is mostly used in the areas
where you need a strong signal. LPDA is available in various shapes and can be
used for two-way communication that needs multiple frequencies.
Disadvantages of a log periodic antenna
Like multiple benefits, the log periodic antenna also has many disadvantages such
as:
 Costly antenna
One of the biggest Disadvantages of Log Periodic Antennas is their cost. These
antennas are costlier than other kinds of antennas because of their simple design,
multiple dipole elements, and use of good materials to make them. This antenna
is mostly used in large commercial and residential areas to gain good signals.
 Low gain

3. A log periodic antenna has a lower gain than Yagi antennas of the same size. It
also has a low gain per unit of weight or wind load. You will need a large log
periodic antenna for better VSWR performance. This performance is not gained in
a small LPDA.
 Multiple elements
We discussed in the above section that an LPDA has multiple dipole elements
with different lengths. It will not work effectively for lower frequencies in HF and
VHF bands without adding the elements. LPDA cannot be used in any
omnidirectional applications as it is a kind of Directional Antenna with a low
polarization ratio.
 Needs a strong platform
Mounting a log periodic antenna on any platform is not easy because of the
various dipole elements. You will need a good mounting platform for a log
periodic antenna as it has many elements.
Major features of a log periodic antenna
Now, let us have a look at some major features of a log periodic antenna in this
section:
 The structure in a log periodic antenna must radiate to the short element
and be negligible to the right direction to get a unidirectional radiation
pattern.
 In a single active region, the excitation to the LPDA is offered at a shorter
length side. On the other hand, the excitation to LPDA in two active regions
is offered at the center of the antenna.
 The magnitude and phase of the currents in a log periodic antenna must be
proper in the active region to get better radiation patterns.
 Log periodic antenna provides both bidirectional and unidirectional
radiation patterns depending on the log periodic structures.
 You will gain a unidirectional radiation pattern in a structure in a single
active region.
 Two active regions will provide a bidirectional radiation pattern.
 The structure of a log periodic antenna is compact and small.

4. Final words
These are the major Advantages of Log Periodic Antennas with structure, design,
features, and certain disadvantages. A log periodic antenna is similar to a Yagi
antenna with certain differences as well. It is widely used for the purpose of high-
frequency communication.
Log periodic antennas are also used for TV reception as they contain multiple
elements that give good directivity. It can work only in the active region. You can
get high-quality log periodic antennas today on the official sites of the
manufacturer.