 Good morning everyone. Myself Piyusha Shedgar, Assistant Professor, Valchan Institute of Technology, Solapur. In today's session, we will see the Helical Antenna, one of the type of Antenna. These are the learning outcomes for today's session. At the end of this session, students will be able to list the features of Helical Antenna. They will be able to explain the working of Helical Antenna. These are the contents will be discussed in today's session. So before going to start, the Helical Antenna, you can pause the video here for a second and recall that the basic function of an Antenna. Yes, Antenna is a transducer which converts electrical power into electromagnetic waves and vice versa. So whenever the Antenna works as a transmitter, it transmits the signal and at the receiver side, it converts one form of energy into other form of the energy and thus Antenna works as a transducer. Now let us discuss the overview of the Helical or Helix Antenna. Helical Antenna is also called as Helix Antenna. So Helical Antenna is an example of the wire Antenna. So there are the different types of the Antenna. So one of the Antenna type is the wire Antenna. Helical is the example of wire Antenna. The shape of the Helical Antenna is, forms the shape of a Helix. So that means the conductor is having the shape of the Helix structure and therefore it is called as a Helical Antenna. So it is a type of broadband Antenna and it is also the very high frequency and ultra high frequency Antenna. This Antenna is used in the range of the frequency about 30 MHz to 3 GHz range. This Antenna works in very high frequency and ultra high frequency ranges. Now these are the example of the Helix Antenna. This figure shows the Helical Antenna. So this is the Helical Antenna. From the first figure you can observe that these are the arrays of the Helical Antenna. So number of Helical Antenna are connected to form a single element. Thus the array of the Helical Antenna is formed. In the second figure you can observe that this is the Antenna conductor which having the Helical shape and thus form the Helical Antenna with the ground plate is connected to the feed point. Now actually the geometry of the Helical Antenna denotes with this figure. So in the first figure you can observe that this is nothing but actually the coaxial input is applied here. Metal ground plane is connected here and here the Helical conductor is placed. Okay so from this figure you can observe that this is the Helical shape the conductor which having the Helix shape with the tubular or the solid metal. This small denotes actually the diameter of the coil. This is nothing but the length of the one loop one turn is denoted with the capital L. S denotes the spacing between the number of turns. So you can take the number of turns of that conductor to form a Helical structure. This is another figure used for the Helical structure. Here you can observe that the conductor which having the Helical shape with the total length denotes with the letter capital L. This is nothing but considered as the diameter of the Helix and this is connected to the ground plane. At the ground plane the field point is mentioned here. Now let us discuss the structure of the Helix. So it is the structure of the Helix so this is again the Helical shape of the conductor is shown with the center point is called as the Helix axis. This total length is denoted with the capital A. So capital A is nothing but the axial length of the Helix. It is given by N times S that is N multiplied with the S. So N is nothing but the number of turns whereas the S is the spacing between the turns. So for designing of the Helical antenna some of the elements are required. So these elements are nothing but actually the diameter of the Helix turns spacing between the center to center point length of the complete turn along with the pitch angle. So the important element for the Helical antenna is the diameter of the Helix. It is given by this letter capital D letter. So when you says that this is nothing but the diameter of the Helical antenna capital D is the diameter of the Helical antenna it decides the circumference of the Helix. So circumference of this Helical antenna is given by pi times D whereas the D is the diameter of the Helical antenna. So from this figure if you are considering a single unwound turn of Helix. So if it is unwound turn of Helix with the total length denotes with the capital letter L this is the spacing between the two turns whereas this is nothing but the circumference. Circumference is given by the equation pi times D. So these two are perpendicular to each other and the angle formed by this perpendicular and the normal to the Helix axis is denotes with the letter alpha. So this alpha is called as the pitch angle. So from this figure you can calculate the L, S, C parameter. These are the elements important to design the Helical antenna. So by using Pythagoras theorem you can define the equation for this L. L is the length of the Helix. So it is given by under root S square plus C square where S is the spacing and C is the circumference. And from this figure you can observe that the alpha can be calculated by taking the tangent value of this alpha. So tan alpha can be calculated by the opposite side upon the adjacent side. So tan alpha can be written as S upon C. So you know that C is the circumference given by this pi times of D. So it can be written as tan alpha equal to S by C. So we have to find out the equation for the alpha. Alpha is equal to tan inverse of S by C whereas C can be replaced with pi times of D. Thus you can observe that the alpha can be calculated by using tan inverse of S and S by C. That means the alpha pitch angle depends on the element the spacing between the two turns of helix. Now there are the special cases of the helical antennas for the pitch angle. Whenever the pitch angle alpha is equal to 0 the meaning of this is whenever the space alpha is equal to 0 the spacing between the two turns becomes equal to 0. That is the S element becomes equal to 0. So as there are a number of turns meaning of this is the number of turns are overlapped to each other. Whenever these number of turns are overlapped to each other it forms the multi loop structure of an antenna. So when the alpha is equal to 0 S becomes equal to 0 and it is loop antenna. For the case 2 when alpha is equal to 90 degree in that case the diameter becomes equal to 0. So meaning of this is S is the spacing between these two becomes infinite. So whenever this becomes infinite that means it acts as a single line. So whenever the alpha is equal to 90 degree it is an linear antenna and when the alpha lies between 0 to 90 degree then it is a helical antenna. Now how to define this peach angle? Peach angle alpha is the angle between a line tangent to the helix wire and the plane normal to the helix axis. The radiation of the helical antenna depends upon this element the spacing diameter and the peach angle. Now this is the construction of the helical antenna. So conductor is wound with this helical shape with the central support is provided and this is connected to the reflection or base or the ground plane and the coaxial cable is connected here and the spacers are provided for as a support between these loop. Helical antenna or the helix antenna is the antenna in which the conducting wire is wound in helical shape and connected to the ground plate with the feeder line with the inner conductor and the outer conductor. It provides the circularly polarized wave that means for the helical antenna circular polarization is obtained that is EM wave having the vertical as well as the horizontal components. It consists of a helix of thick wire, steel or brass wire wound in a shape of a screw thread. It is used as an antenna in conjunction with a flat metal plate called the ground plate. So one end of the helix is connected to the center conductor of a cable and is the outer conductor is connected to the ground plate. So the impedance of a helical antenna depends on the number of parameters. So these parameters are coil diameter, coil loop pitch, coil length and the frequency. These are the references used for today's session.