University of the East College of EngineeringECE Department

Design Experiment No.1Yagi Uda Antenna

ECN 515/2AFRI / 2:30AM 5:30 PM

Submitted by:Submitted to: Briones, John David A.Engr. Michael S. MatiasCaab, Allan Charles T.Dominguez, Jose Victorio E. Documentation (20%)_____Dueas, Stephen Hicy B.Circuit (80%) _____Espiritu, Christian Aerol M.Novilla, Ashner Gerald P.

INTRODUCTION: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 so-called 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 re-introduced 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 BasicsThe 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

14 ft. Boom

11 ft. Element

3Element holder

1Balun

6Element caps

3Boom caps

110 ft. Coaxial cable

2Coaxial cable connectors

COMPUTATION:= ft = ft = [ 984/fMHZ ] (ft /2) = [492/fMHZ]Target Ch. 23

flow = 524 MHzflow = [ 6 (23) + 386 ] MHz

Length of the DipoleCh. 23RANGE = 524 MHZ 530MHZ

0.9283018868 ft or 11.1396 in. or 28.2946 cm(ft /2) = 492/530 =

1.857 ft. or 56.6014 cm or 22.284 inft = 984 / 530 =

Length of the Reflector

0.9747169811 ft or 11.6966 in or 29.7094 cmLength of the Reflector = (1.05) (0.9283018868 ft) Length of the Reflector =

Length of the Director

0.8818867925 ft or 10.5826 in or 26.8799 cmLength of the Deflector = (0.95) (0.9283018868 ft) Length of the Director =

Length of the Distance between Reflector, Dipole, and Director

0.27855 ft or 3.3426 in or 8.4902 cmLength of the Distance = (0.15) (1.857 ft)Length of the Distance =

0.27855 ft or 3.3426 in or 8.4902 cm

0.27855 ft or 3.3426 in or 8.4902 cm

DirectorDiploleReflector/2 included the space0.8818867925 ft or 10.5826 in or 26.8799 cm0.9283018868 ft or 11.1396 in. or 28.2946 cm0.9747169811 ft or 11.6966 in or 29.7094 cm

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 =. 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=. In determining the length of each driven element. The value of ft is halved which is equal to =. Substituting the value of the fMHz. Which is from the formula flow = [ 6 (Given channel) + 386 ] MHz. using this formula gave us a value of flow= 524 MHz. Therefore=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 amicroammeter, which is scaled indB. 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.