In this chapter, we shall discuss about another important factor in the radiation pattern of an antenna, known as beam width. In the radiation pattern of an antenna, the main lobe is the main beam of the antenna where maximum and constant energy radiated by the antenna flows.
Beam width is the aperture angle from where most of the power is radiated. In other words, Beam width is the area where most of the power is radiated, which is the peak power.
This can be well understood with the help of the following diagram. Simply, FNBW is the angular separation, quoted away from the main beam, which is drawn between the null points of radiation pattern, on its major lobe. Draw tangents on both sides starting from the origin of the radiation pattern, tangential to the main beam. The above image shows the half power beam width and first null beam width, marked in a radiation pattern along with minor and major lobes.
Among the antenna parameters, the effective length and effective area are also important. This polarization should match with the magnitude of the voltage at receiver terminals.
The whole area of an antenna while receiving, confronts the incoming electromagnetic waves, whereas only some portion of the antenna, receives the signal, known as the effective area.
Only some portion of the received wave front is utilized because some portion of the wave gets scattered while some gets dissipated as heat. Hence, without considering the losses, the area, which utilizes the maximum power obtained to the actual area, can be termed as effective area.
Antenna Theory - Beam Width Advertisements. Previous Page. Next Page. Previous Page Print Page.Leave us a question or comment on Facebook. Com All Rights Reserved. This calculator is designed to give the critical information of a particular beam antenna, in this case a three element Yagi, for the frequency chosen. Enter the desired frequency then click on Calculate and the optimum values for that combination will be displayed in feet, inches and fractions of inches, and in meters.
To optimize the antenna for a frequency RANGE, do the calculations twice, once for the low end of the range and once for the high end; then average the two and plan to adjust the VSWR on both ends of the range as needed. As general information, the director is the shortest element, the driven element is the middle element in a 3 element beam and the reflector is the longest element. Spacing is on the antenna bar holding the elements, with equidistant spacing from each of the outside elements to the driven element.
Direction of the strongest transmitted signal is from the reflector toward the director. Reception is the reverse. Search or Browse Our Site.A Yagi-Uda antennacommonly known simply as a Yagi antennais a directional antenna consisting of multiple parallel dipole elements in a line,  usually made of metal rods. The antenna was invented in by Shintaro Uda of Tohoku Imperial UniversityJapan with a lesser role played by his colleague Hidetsugu Yagi.
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.
The largest and most well-known use is as rooftop terrestrial television antennas but it is also used for point-to-point fixed communication links,  in radar antennas,  and for long distance shortwave communication by shortwave broadcasting stations and radio amateurs.
The Yagi-Uda antenna consists of a number of parallel thin rod dipole elements in a line, usually half-wave dipoles typically supported on a perpendicular crossbar or "boom" along their centers. The lengths of the directors are slightly shorter than that of the driven element, while the reflector s are slightly longer. Conveniently, the dipole parasitic elements have a node point of zero RF voltage at their center, so they can be attached to a conductive metal support at that point without need of insulation, without disturbing their electrical operation.
The gain increases with the number of parasitic elements used. The bandwidth of the antenna is the frequency range between the frequencies at which the gain drops 3 dB one-half the power below its maximum. The Yagi-Uda array in its basic form has very narrow bandwidth, 2 - 3 percent of the center frequency.
Yagi-Uda antennas used for amateur radio are sometimes designed to operate on multiple bands. These elaborate designs create electrical breaks along each element both sides at which point a parallel LC inductor and capacitor circuit is inserted.
This so-called trap has the effect of truncating the element at the higher frequency band, making it approximately a half wavelength in length. At the lower frequency, the entire element including the remaining inductance due to the trap is close to half-wave resonance, implementing a different Yagi-Uda antenna.
Using a second set of traps, a "triband" antenna can be resonant at three different bands. Given the associated costs of erecting an antenna and rotor system above a tower, the combination of antennas for three amateur bands in one unit is a very practical solution. The use of traps is not without disadvantages, however, as they reduce the bandwidth of the antenna on the individual bands and reduce the antenna's electrical efficiency and subject the antenna to additional mechanical considerations wind loading, water and insect ingress.
Consider a Yagi-Uda consisting of a reflector, driven element and a single director as shown here. All the other elements are considered parasitic. That is, they reradiate power which they receive from the driven element they also interact with each other. One way of thinking about the operation of such an antenna is to consider a dipole element to be a normal parasitic element with a gap at its center, the feedpoint. Now instead of attaching the antenna to a load such as a receiver we connect it to a short circuit.
As is well known in transmission line theory, a short circuit reflects all of the incident power degrees out of phase. So one could as well model the operation of the parasitic element as the superposition of a dipole element receiving power and sending it down a transmission line to a matched load, and a transmitter sending the same amount of power down the transmission line back toward the antenna element.
If the wave from the transmitter were degrees out of phase with the received wave at that point, it would be equivalent to just shorting out that dipole at the feedpoint making it a solid element, as it is. Thus, one can appreciate the mechanism by which parasitic elements of unequal length can lead to a unidirectional radiation pattern. While the above qualitative explanation is useful for understanding how parasitic elements can enhance the driven elements radiation in one direction at the expense of the other, the assumptions used are quite inaccurate.
Since the so-called reflector, the longer parasitic element, has a current whose phase lags that of the driven element, one would expect the directivity to be in the direction of the reflector, opposite of the actual directional pattern of the Yagi-Uda antenna. In fact, that would be the case were we to construct a phased array with rather closely spaced elements all driven by voltages in phase, as we posited.There have been minor fixes to improve reliability in different machines and better program flow.
No changes were made to the essential algorithms apart from the additions needed to cater for alternate boom and element material shapes. If you run Vista I recommend you run it as Administrator. YC now produces. Features of the free but copyrighted program include: calculation of the element length and element spacings of a yagi for a particular frequency, different size materials for boom and elements are catered for as are different methods of mounting, dimensions of baluns are calculated, there is provision for entering the dimensions of an existing DL6WU antenna for optimisation through an external program or to gather information on its gain, beamwidth etc.
A handy SWR calculator and feedline loss calculator are included as part of the package. Stacking information is also provided as are estimates of gain. A helpfile is included that covers many aspects of yagi design as well as helping with the operation of the program. Note: where countries use a comma for decimals you may need to change your country code otherwise MMANA files will not run.
Yagi Calculator is a Windows program that also runs well on Linux, Ubuntu 8. Long yagis are commonly used from the MHz amateur band to the 2. The DL6WU yagi is highly regarded as being easy to build with repeatable results, broad bandwidth and a useful pattern. The program on this site was developed in the early 90s as a DOS program. Time moved on and so did operating systems, so the version was an opportunity to convert to a Windows environment and update the information and modify some of the algorithms.
Latest Version is 2. Version 2. A materials list has been added to the yagi printout to assist with the buying process but be wary that this is a calculated measure and does not allow for saw cuts and wastage from short purchased lengths. The output screen. Click here to download the installation package. Yagi Calculator is a program to assist with the design of long yagi antennas. The article was titled Extremely Long Yagi Antennas. For best front to back ratio it is recommended that a yagi be constructed with one of the following numbers of elements - 10,14,19, Yagi builders are reminded that DL6WU designs are primarily for long yagis.
A boom length of 2 wavelengths or 10 elements would be a minimum sized antenna. On the other hand, yagis with as few as 8 elements have used the design and worked very well. The author acknowledges the ARRL Handbook for information on coaxial cable impedance, dielectric and velocity factor.
Some valuable comments on scaling and boom diameters from W4RNL.Here is a simple antenna calculator for two popular forms of ham radio HF wire antennas: the horizontal dipole and the inverted "V".
Enter your desired frequency MHz of operation i. If you have no particular preference within a given ham radio band, then simply enter its center frequency i. To fully understand the results obtained by this calculator, please take a few minutes to read the explanation below it. Be prepared to trim the ends of the inverted V dipole if the final frequency of resonance ends up being too low for your needs when the inverted V is installed in its permanent position.
The antenna calculator above uses this formula as a starting point to calculate wire lengths for the dipole. The results are conveniently displayed in inches, centimeters, feet and meters.
This formula to obtain the length of a half-wave dipole antenna will give a good ballpark value to start with. However, the actual resulting frequency of resonance and feed-point impedance of a dipole will depend on:. When each side of a dipole slopes down from the feed point, it is commonly called an inverted V. But if one were to actually do that, the inverted V would resonate at an even higher frequency!
This will give you some leeway to trim the wire ends back if the inverted V resonates too low for your purpose when installed in its final position. The formula used by the calculator to compute the wire lengths for the inverted V is based on the formula for a half-wave dipole. It is adjusted to take into account the special characteristics of the inverted V.
In the case of the inverted V we must add - to the list of environmental variables influencing the half-wave dipole - the angle between the two legs of the inverted V. The angle below the two sections of a horizontal dipole is degrees. As the two sections of the dipole are lowered below the feed point, the angle between the two legs decreases:. To avoid the latter outcome, the antenna calculator above is set up to compensate somewhat for local adverse environmental conditions.
The length it will calculate will likely be a little too long. You will only have to trim it a few inches at a time to bring the frequency of resonance up to where you want it. For more detailed information on ham radio HF wire antennas, please visit this section of our Web site. If the angle between the two legs of the inverted V becomes less than 90 degrees, the radiation patterns from each leg of the inverted V begin to interact and cancel each other to some extent.
Therefore, the angle between the two legs of an inverted V should not be less than 90 degrees. Remember, an inverted V requires slightly more wire than a horizontal dipole for a given frequency of resonance. The antenna calculator above will provide appropriate wire lengths for the inverted V and the dipole for a given frequency of your choice.
I am sharing this fitting video with you in these most challenging times. Let's keep the communication channels open while, by civic duty, we must maintain a vital physical distance from our fellow me…. Read More.The design of a Yagi-Uda antenna is actually quite simple. Because Yagi antennas have been extensively analyzed and experimentally tested, the process basically follows this outline: Look up a table of design parameters for Yagi-Uda antennas Build the Yagi or model it numericallyand tweak it till the performance is acceptable As an example, consider the table published in "Yagi Antenna Design" by P Viezbicke from the National Bureau of Standards,given in Table I.
Note that the "boom" is the long element that the directors, reflectors and feed elements are physically attached to, and dictates the lenght of the antenna. Table I. There's no real rocket science going on in the above table. I believe the authors of the above document did experimental measurements until they found an optimized set of spacings and published it.
The spacing between the directors is uniform and given in the second-to-last row of the table. The above table gives a good starting point to estimate the required length of the antenna the boom lengthand a set of lengths and spacings that achieves the specified gain. In general, all the spacings, lengths, diamters including the boom diameter are design variables and can be continuously optimized to alter performance. There are thousands of tables that further give results, such as how the diamter of the boom affects the results, and the optimal diamters of the elements.
The resulting antenna has a Figure 1. E-plane gain of Yagi antenna. Figure 2. H-Plane gain of Yagi-Uda antenna. Figure 3. The above plots are just an example to give an idea of what the radiation pattern of the Yagi-Uda antenna resembles.
The gain can be increased and the pattern made more directional by adding more directors or optimizing spacing or rarely, adding another refelctor. The front-to-back ratio is approximately 19 dB for this antenna, and this can also be optimized if desired. No portion can be reproduced or copied except by permission of the author.The kids loved it Thanks again, Janine" Updated November 19, There are several things you need to do to "catch" the radio signal reflected from a meteor ionization trail.
The antenna is the instrument that does this. To put up an antenna you will need to consider the following points:. An antenna is an electromagnetic device that collects or emits radio waves. It consists of material that conducts electricity arranged in such a way that it is in tune with the frequency of a radio signal. Like a tuning fork in the presence of a sound of the same pitch, an antenna tuned to a particular frequency will resonate to a radio signal of the same frequency.
When properly tuned an antenna will collect this energy and make it available to drive the amplifiers in a radio receiver making it possible for the human ear to hear the signal. Radio signals are at a frequency that cannot be heard by the human ear and they are so weak they cannot be detected without an antenna and radio receiver. Also, radio signals travel in the form of waves of photons - the same thing as light - but these photons are at a much longer wavelength than light and can't be detected by the human eye, which are "tuned" to see light waves.
Sound travels in waves through molecules of air, water, or other material. Radios convert waves of photons into waves of sound. For the detection of meteors, we need to construct and attach an antenna to the radio. This section describes how to do this.
Yagi is the name of the Japanese man who designed this type of antenna. It is very easy for the amateur to build using materials such as clothes hangers or copper wire used for house wiring. If you can run a wire from your classroom outside to the roof of your school or other suitable location to set up your antenna, a three element Yagi antenna is recommended.
It will efficiently collect the radiated energy of a distant FM radio station whose waves have been reflected by a meteor trail. We have tested this antenna and it has been used successfully in our test schools. If you wish to learn more about antenna design, continue reading, otherwise, proceed to your next topic of interest. The Reflector is at the back of the antenna furthest away from the transmitting station.
In other words the boom of the antenna is pointed towards the radio station over the horizon with the Reflector furthest away from the station.
2 Element Beam Calculator
The Driven Element is where the signal is intercepted by the receiving equipment and has the cable attached that takes the received signal to the receiver. There are formulas that you can use to decide both the length of the pieces and the spacing between them. The dimensions of the elements is frequency-dependent. Here are the general rules for length :. What this formula embodies is related to the speed of light.Yagi Uda Basic Design and Construction - Easy Antenna Tutorial
Another way of putting it is that the length of the waves you will be detecting with your antenna is calculated by dividing the speed of lightmeters per second by the frequency you'll be observing at, let's say A Hertz is one cycle per second. That means one vibration per second.
Antenna Theory - Beam Width
A Megahertz is one million cycles per second. So See the article on The Electromagnetic Spectrum in the Library part of this website for more information on radio waves.
To determine the wavelength of a radio station with a frequency of The seconds cancel out in the formula with the wavelength ending up at 3. In other words the waves passing you by right now from a radio station transmitting at