Investigation Of A Turner Circuit - Essay Example

INVESTIGATION OF A TURNER CIRCUIT location In the communications industry, tuning circuits have proven to be of significance, especially in the case of Am and Fm transmissions. There are various forms of circuits in the market and this differs based on the location of use. This report bases on an oscilloscope whose function is monitoring the circuit’s output waveforms in the demonstration of frequency selections. The function of an oscilloscope in this report is display of output as more features of the curves presented can be shown alongside the curve. There also is the use of a function generator is added in order to help in generating waveforms to get filtered by the circuit. The lab report is detailed on the testing as well the design used in the construction of a tuner circuit. Being that students are supposed to actively take part in the practical in terms of setting frequencies before checking output waveforms, they become better at understanding the operation of the tuner circuit. In this report, therefore, emphasis is on assessing a tuner circuit in order to understand its features better. Table of Contents Abstract 2 List of Figures 4 List of Tables 4 1.0 Introduction 5 2.0 Design 6 2.1 Experiment setting 6 2.2 Output data record 7 3.0 Results 8 3.1 Results of the 76.99 kHz signal 8 3.2 Results of the 66.09 kHz signal 8 Discussion 10 Conclusion 11 List of Figures Figure Page Fig 1: Output at 76.99 kHz 9 Fig 1: Output at 76.99 kHz 10 List of Tables Table Page Table 1 The results at 76.99 kHz 9 Table 2 The results at 66.09 kHz 10 1.0 Introduction A circuit allowing an output only at a given frequency forms a tuner circuit. The use of a turner circuit is mainly in the communications industry for selecting of channels. Besides, it plays the role of a sub-system in that it concerts selected carrier frequency as well as its bandwidth into a fixed frequency that is in turn proper in processing from the received radio frequencies (RF). The AM/FM broadcast transmissions then feed the demodulator with the intermediate frequency (IF) and the demodulator in turn converts the radio signal into audio-frequency signals that enable driving a loudspeaker. Applications of wider frequency bandwidth are in transmissions that are more complicated such as DVB-S/DVB-T/DVB-D in digital TV, PAL/NTSC in TV and DAB for digital radio. Frequency bandwidths are equally transmitted as IFs with the use of several sub-carriers in the receiver. If the whole bandwidth undergoes sampling with A/D at a faster rate, the sub-carrier processing takes place (Learn about Electronics.com, 2011). The expected rate is at least twice the IF frequency. The simplest tuner from a circuit connection of a capacitor and an inductor is the radioactive crystal. The inductor or the capacitor is made to be variable to create a resonant circuit that responds at a particular frequency to an alternating current. Addition of the demodulator to a tuner as a detector results in the production of the smallest unit of the radio receiver called the crystal. Practically, radio receivers use a super-heterodyne receiver while the older models would use ganged variable capacitors that are mechanically operated to realize manual tuning. Often there were several provisions for sections on a tuning capacitor to allow for switching between different frequency bands or to tune various stages of the receiver in tandem. A tuner can also be a radio receiver or any standalone audio component forming part of a sound system connected to a separate amplifier. Tuning as a verb would be used in a radio context to mean the process of adjusting the receiver of a radio to receive the desired radio signal carrier frequency that is being utilized by a particular radio station. 2.0 Design 2.1 Experiment setting In this experiment, there was use of a function oscilloscope and generator. Two resistors got used, a D.C. power supply (10v), inductor (47mH), BC108 transistor, capacitor (22pF, 6.8nF), (1k, 3k, 470Ω). Having identified the used components, it was then important stating their properties. There was the use of a column shaped breadboard in the connecting of the generator to the circuit input with the signal of entry of 100mV peak-to-peak and 5 kHz. The function generator’s ground terminal consisted of a looping with 470 Ω resistor and 1k resistor. The function generator’s feeding of the signal generator took place at the base of a BC108 transistor through a voltage divider of 3.9 k and 1k resistors. Before the voltage division process, a capacitor (6.8 nF) received the signal first from the function generator before the voltage division process (Hans, 2014). There was the connection of BC108 transistor in a manner that there was a connection of the collector to the positive power terminal and the oscilloscope. Also, there is the connection of the emitter’s terminal with the ground through the 470Ω resistor; again with the base terminal on the function generator output to the voltage divider circuit and the 6.8 nF capacitor. The 47 mH inductor and 22 pF capacitor power arrangement consisted of loops between the transistor collector terminal and 10v power supply. This terminal was then tapped and through a 6.8 nF capacitor to the oscilloscope. The voltage was then set by use of one channel of the oscilloscope. In the course of this connection, the accuracy of the process was not taken much into consideration (Ian, 2015). The oscilloscope last part’s channel was connected to the output. As the signal frequency of the input increased, it was important to note the output signal as well as the generated waveform. 2.2 Output data record There was recording of transmitted signals of the peak voltage amplitudes as well as the received ones as far as all frequencies are concerned, in a table. The results on the oscilloscope got captured via screen shots. It was important taking the screen shots as they got useful in the waveform drawing of the output signals. In the event of these, it was necessary to take notes, given the disparity in the received and transmitted signals. 3.0 Results 3.1 Results of the 76.99 kHz signal Fig 1 Output at 76.99 kHz Table 1 Results of the 76.99 kHz transmitted signal. The transmitted signal is at a peak voltage of 50mV while the received has a peak voltage of 5V. Channel Number Y Gain Peak Voltage (Volts) 1 0.50 0.05 2 5.00 5.00 Table 1 The results at 76.99 kHz 3.2 Results of the 66.09 kHz signal Table 1 Results of the 76.99 kHz transmitted signal. The signal transmitted is at a peak voltage of 50mV while the received one has a peak voltage of 5V. Fig 2 Output at 66.09 kHz Channel Number Y Gain Peak Voltage (Volts) 1 0.50 0.05 2 5.00 5.00 Table 1 The results at 66.09 kHz The oscilloscope was found to produce ragged waveforms at a higher frequency (76.99 kHz). There then was the waveform crashing in order to create the illusion of it being smaller during the experiment. Upon the frequency moving down to 66.09 kHz, the output waveform was smoothened into a clear larger sine wave. In the event of a change in frequency, therefore, the waveform changes too. Discussion Resonant circuits are in two types; parallel or series. It is important for one to aware of potential high voltages especially when working with any electrical circuits like resonant. A resonant circuit can be compared to a tank circuit. This is usually considered so because the circuit is capable of storing its energy from the power sources in either the inductors or capacitors. A continuous AC waveform is produced in the process as the output. The number of times that events occur per second, just as a set, is what is known as a resonant frequency. In this report, the turner circuit used can be compared to a parallel LC circuit that has its current minimum and the impedance at maximum. Here, the variable which is the current is at a point where there are two currents that are out of phase with each other at 180 degrees. Below resonance, the current is inductive while above resonance it becomes capacitive. In terms of operation, resonant circuits’ XC and XL can only get equal to resonance frequency. This can be explained by the fact that the principle enables the radio receiver’s tuned circuits to be able to choose one frequency at a time. The tuned circuit’s resistance is known to have limited inherent resistance to components such as coil’s resistance. There are various applications of the circuit to daily life as well as in many electronic devices, which is why the study of circuits is of much importance. The application of circuits ranges from simple to sophisticated devices such as sophisticated space satellite and model airplanes. This occurs in a way that there are emissions emitted by the antenna through charged particles when in acceleration and movement of electrons in and out noted by the AC voltage from the AFG. It is the AC voltage that accelerates the electrons causing emission of radio waves travelling to the broadcasting antenna perpendicularly. In this case, therefore, setting up the antenna responsible for the transmission, parallel to the receiving antenna is required. Conclusion The application areas of resonant circuits are diverse, ranging from electronic field devices in the navy, radio, communications, television, among others. In order to control the resonance frequency of the circuit, a variation in the inductor or capacitor is crucial. The resonance circuits work through separation of other frequencies from certain frequency currents and in the process select stations as well as tune, in the event of selecting a particular channel. In order to produce a filter network or frequency selector, it is necessary for one to make a proper selection of capacitors, resistors or inductors. This filter network makes it possible for frequencies to be chosen indiscriminately. There also is another design of filters that is able to select frequency bands and ignore all the others. These filters are necessary in electronic devices as close to all electronic devices make use of the filters in a variety of ways. A perfect example of such resonant circuits is the rectifier circuit that changes an alternating current to a direct one, though the voltage of the DC continues to pulsate and fluctuate due to its impurity; which, therefore is to mean that the AC component is still present. In cases where the AC is not required, one could use a bypass capacitor in ensuring that the un-required components are left out. Before hearing a sound or seeing a picture, there are various steps that happen in the receiver in the event of this transmission. In the process, the radio antenna is reached by different signals at the same time. It is then the duty of the receiver to tune the radio in order to select the station of their choice. The listener is forced to adjust the tuning dial on the radio receiver until a desired station for selection. It is the tuned circuit in television and radio receivers that automatically chooses the desired signal, ignoring the undesired ones. Therefore, the resonance principle occurs when the characteristics of capacitance and inductance are in a tuned circuit. References Hans, E., 2014. Tuned Circuits. [Online] Available at: http://www.hans-egebo.dk/Tutorial/tuned_circuits.htm [Accessed 8 December 2015]. Ian, C. P., 2015. Tuned Circuit Amplifiers. [Online] Available at: http://www.electronics-tutorials.com/amplifiers/tuned-circuits.htm [Accessed 8 December 2015]. Learn about Electronics.com, 2011. Learn about Electronics.com. [Online] Available at: http://www.learn-about-electronics.com/tuned-circuits.html [Accessed 8 December 2015]. Read More