Yagi Uda Antenna Equation

University of the East
College of Engineering
ECE Department
Design Experiment No.1
Yagi Uda Antenna
ECN 515/2A
FRI / 2:30AM 5:30 PM
Submitted by:
Briones, John David A.
Caab, Allan Charles T.
Dominguez, Jose Victorio E.
(20%)_____
Dueas, Stephen Hicy B.
Espiritu, Christian Aerol M.
Novilla, Ashner Gerald P.
INTRODUCTION:
Submitted to:
Engr. Michael S. Matias
Documentation
Circuit (80%) _____
A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional

antenna consisting of a driven element (typically a dipole or folded dipole) and additional
parasitic elements (usually a so-called reflector and one or more directors). The reflector
element is slightly longer (typically 5% longer) than the driven dipole, whereas the socalled directors are a little shorter. This design achieves a very substantial increase in
the antenna's directionality and gain compared to a simple dipole.
Highly directional antennas such as the Yagi-Uda are commonly referred to as
"beam antennas" due to their high gain. However, the Yagi-Uda design only achieves this
high gain over a rather narrow bandwidth, making it useful for specific communications
bands. Yagi antennas were first widely used during World War II for radar systems, and
were widely used by the British, US and Germans. Large Yagi arrays were particularly
evident on German night fighters. Inter-service rivalries and the military's distrust of all
things civilian resulted in no use in Japan until late in the war, when the device was reintroduced via foreign technical articles captured in Singapore. In the post-war era, the
Yagi found extensive use with amateur radio operators ("hams"), who frequently employ
these on HF, VHF, and UHF bands, often constructing antennas themselves
("homebrewing"), leading to a quantity of technical papers and design software.
The name stems from its inventors, Shintaro Uda of Tohoku Imperial University,
Japan, with a lesser role played by his colleague Hidetsugu Yagi. However the "Yagi"
name has become more familiar with the name of Uda often omitted. This appears to
have been due to Yagi filing a patent on the idea in Japan without Uda's name in it, and
later transferring the patent to the Marconi Company in the UK.
Yagi-Uda: The Basics
The Yagi antenna design has a dipole as the main radiating or driven element.
Further 'parasitic' elements are added which are not directly connected to the driven
element.
These parasitic elements within the Yagi antenna pick up power from the dipole
and re-radiate it. The phase is in such a manner that it affects the properties of the RF
antenna as a whole, causing power to be focused in one particular direction and
removed from others.
The parasitic elements of the Yagi antenna operate by re-radiating their signals in
a slightly different phase to that of the driven element. In this way the signal is
reinforced in some directions and cancelled out in others. It is found that the amplitude
and phase of the current that is induced in the parasitic elements is dependent upon
their length and the spacing between them and the dipole or driven element.
Yagi Antenna Advantages:

The Yagi antenna offers many advantages for its use. The antenna provides many
advantages in a number of applications:
Antenna has gain allowing lower strength signals to be received.
Yagi antenna has directivity enabling interference levels to be minimised.
Straightforward construction. - the Yagi antenna allows all constructional elements
to be made from rods simplifying construction.
The construction enables the antenna to be mounted easily on vertical and other
poles with standard mechanical fixings
The Yagi antenna also has a number of disadvantages that need to be considered:
For high gain levels the antenna becomes very long
Gain limited to around 20dB or so for a single antenna
The Yagi antenna is a particularly useful form of RF antenna design. It is widely

used in applications where an RF antenna design is required to provide gain and
directivity. In this way the optimum transmission and reception conditions can be
obtained.
MATERIALS USED:
Quantity
Item
1
1
3
1
6
3
1
2
4 ft. Boom
1 ft. Element
Element holder
Balun
Element caps
Boom caps
10 ft. Coaxial cable
Coaxial cable connectors
COMPUTATION:
c
f
(3 x 10 ms )( 3.21 mft )
8
ft =
( 1 x 106 ) f MHZ
ft = [ 984/fMHZ ]
(ft /2) = [492/fMHZ]
Target Ch. 23
flow = [ 6 (23) + 386 ] MHz
flow = 524
Ch. 23RANGE = 524 MHZ 530MHZ
(ft /2) = 492/530 =
Length of the
Dipole
0.9283018868 ft or 11.1396 in. or 28.2946
ft = 984 / 530 =
1.857 ft. or 56.6014 cm or 22.284 in
Length of the Reflector
Length of the Reflector = (1.05) (0.9283018868 ft)

Length of the Reflector =
0.9747169811 ft or 11.6966 in or 29.7094
Length of the Director

Length of the Deflector = (0.95) (0.9283018868 ft)
Length of the Director =
0.8818867925 ft or 10.5826 in or 26.8799
Length of the Distance between Reflector, Dipole, and Director
Length of the Distance = (0.15) (1.857 ft)

Length of the Distance =
0.27855 ft or 3.3426 in or 8.4902
0.27855 ft or 3.3426 in or 8.4902

0.27855 ft or 3.3426 in or 8.4902
/2
included
the space
Director
Reflector
Diplole
0.9747169811 ft or 11.6966 in or 29.7094
0.9283018868 ft or 11.1396 in. or 28.2946

0.8818867925 ft or 10.5826 in or 26.8799
PROCEDURES:
1. Compute for proper lengths of the director, reflector, dipoles, and the distances
between them according to the target frequency.
2. Acquire the materials to be used.
3. Cut the elements to proper lengths in order to represent as the reflector, the
dipole and the director. Cut the boom to proper length to accommodate the
elements, also cut another part of the boom to represent as the holder.
4. Put holes to the boom for the attachments of the element holders, also put holes
to the elements to attach the elements to the element holders.
5. Attach one boom to each of the elements: the dipole, director and reflector.
6. Attach the element holders to the boom, with carefully distancing each element
from each other.
7. Attach the boom which accommodates the elements to the holder.
8. Attach the wire from the balun, to the dipole.
9. Attach coaxial cable connectors to each end of the coaxial cables.
10.Attach a coaxial cable to the other end of the balun.
11.Properly cover the balun.
TECHNICAL DISCUSSION:
In this design experiment, we were asked by our professor to construct and
design a Yagi-Uda antenna for VHF/UHF signal reception.The Yagi-Uda antenna or Yagi
antenna is one of the most brilliant antenna designs. It is simple to construct and has a
high gain, typically greater than 10 dB. The Yagi-Uda antennas typically operate in HF to
UHF bands (about 3 MHz to 3 GHz), although their bandwidth is typically small on the
order of a few percent of the center frequency.
The Yagi-Uda antenna design must receive the operating frequency ranges
of 54MHz -60MHz (channel 2) to524 MHZ - 530MHZ (channel 23). By using the
wavelength formula = f
. We were able to determine the physical length of the
parasitic elements (reflector and director) and the driven element (dipole).With c is equal
to the speed of light in ft/s. The computed value of ft is equal to=
984 ft /s
fMhz . In
determining the length of each driven element. The value of ft is halved which is equal
to =
492 ft /s
fMhz . Substituting the value of the f MHz. Which is from the formula flow = [ 6
(Given channel) + 386 ] MHz. using this formula gave us a value of f low= 524 MHz.
Therefore=
492 ft /s
fMhz is equal to 0.9283018868 ft. Converting the value to centimeters
will yield a length of 28.2946 cm. Multiplying the length by 2 will equate to the total
physical length of the dipole which is 56.6014 cm.
In Computing the physical length of the reflector, We had added 5 percent
of the physical length of a single driven element to itself. By computation Length of the
Reflector = (1.05) (28.2946 cm) which is equal to 29.7094 cm. whereas in computing the
physical length of the Director we had lessen the physical length of a single driven
element to itself. By computationLength of the Deflector = (0.95) (0.9283018868
ft)which is equal to26.8799 cm.
Physical distances of the parasitic elements and
the driven element were also computed by multiplying the physical total length of the
dipole by 0.15 had gave us a value of Length of the Distance = (0.15) (1.857 ft)
converting to centimeters had given us 8.4902 cm. Proper placement of the elements
were also implemented in which the driven elements were placed horizontally placed in
the middle of the boom and the parasitic elements were placed horizontally in the side of
the dipoles with equal distances of 8.4902 cm. A balun which serves as a linkage of the
antenna which is connected to the dipoles and is connected to the coaxial cable that
serves as a connection to a device such as a television set or a TV frequency meter.
In testing the Yagi-Uda antenna design. We had used a Field strength meter
which is actually a simple receiver, the signal is detected and fed to a microammeter,
which is scaled in dB. To test the signal strength of the antenna design. In the initial
testing of the antenna. We had set the meter to Channel 7 in video. We had notice that
the signal strength reads to 77.4 dB and in audio 61.9 dB in the channel 7 audio
setting. We also had noticed the clear audio reception of the channel 7. We also tested
the meter to test channel 2, which reads 49.1 dB for the video and 42.2 dB for the
audio. We also tested channel 9, and its reading for the video is 68.7dB and for audio is
49.8 dB. Then we tested channel 13, its video gave a reading of 77.1 dB and the audio
read 66.2 dB. Then we had set the Field strength meter to Channel 23 and gathered a
video power reading of 22.5 dB and an audio power reading of 31.6dB. Increasing the
gain of the power depends on the location of the antenna and by positioning of the
antenna right.

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University of the East

A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional

Yagi Antenna Advantages:

The Yagi antenna is a particularly useful form of RF antenna design. It is widely

1.857 ft. or 56.6014 cm or 22.284 in

Length of the Reflector

Length of the Reflector = (1.05) (0.9283018868 ft)

0.9747169811 ft or 11.6966 in or 29.7094

Length of the Director

0.8818867925 ft or 10.5826 in or 26.8799

Length of the Distance between Reflector, Dipole, and Director

Length of the Distance = (0.15) (1.857 ft)

0.27855 ft or 3.3426 in or 8.4902

0.27855 ft or 3.3426 in or 8.4902

0.9747169811 ft or 11.6966 in or 29.7094

0.9283018868 ft or 11.1396 in. or 28.2946

. We were able to determine the physical length of the

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