Investigation of a Turner Circuit - Lab Report Example

INVESTIGATION OF A TURNER CIRCUIT location Tuning circuits have found great use in the communications industry as tuners are being employed in FM and Am transmissions. The circuits exist in different forms depending on the exact place the circuit for use. The report tends to focus on one of the simplest circuits of the tuner circuit designed to help monitor the output waveforms of the circuit while demonstrating frequency selections. An oscilloscope is used to display the output as more features of the curves presented can be shown alongside the curve. A function generator is incorporated to assist with the generation of waveforms that the circuit has to filter. The lab report provides a detail view of the construction design and testing of a tuner circuit. The practical would enable students understand the operation of a tuner circuit since the students have to set the frequencies on their own before checking for the output waveforms. The report majorly focuses on investigating a tuner circuit to acquire most of its features. Table of Contents Abstract 2 Table of Contents 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 that allows an output only at a particular frequency forms a tuner circuit. A Turner circuit has its use in the selection of channels in the communications industry. A tuner is also as a subsystem that converts some selected carrier frequency together with its associated bandwidth into a frequency that is fixed and suitable for further processing from the received radio frequency (RF). A demodulator is fed with the intermediate frequency (IF) by the broadcast FM/AM transmissions. The same demodulator helps in converting the radio signal into audio-frequency signals to be fed to drive a loudspeaker. A wider frequency bandwidth has its application in more complicated transmissions like DAB used in digital radio, PAL/NTSC used in TV and DVB-S/DVB-T/DVB-C used in digital TV. Several subcarriers within the receiver are used to transmit the frequency bandwidths as intermediate frequencies (IF). The processing of the subcarriers occurs, or the whole bandwidth underwent sampling with A/D at a faster rate than the Nyquist rate. The expected rate is at least twice the IF frequency (Vendelin, Pavio and Rohde, 2005). 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 superheterodyne 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 (Serway and Vuille, 2007). 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 The experiment made a good use of a function generator and oscilloscope. I used resistors (1k, 3k, 470Ω), capacitor (22pF, 6.8nF), inductor (47mH), BC108 transistor and a D.C. power supply (10v). After the identification of the components used, the next step involved stating their properties. A column shaped breadboard was used to connect the function generator to the input of the circuit with the signal of entry set to 100mV peak-to-peak and 5 kHz. The ground terminal of the function generator had a looping with 1k resistor and 470 Ω resistor. Feeding of the signal generator from the function generator occurred at the base of a BC108 transistor through a voltage divider consisting of 3.9 k and 1k resistors. A capacitor (6.8 nF) first received the signal from the function generator before the voltage division process (Progri, 2011). BC108 transistor was in connection in such a way that the collector had connection to the positive terminal of the power supply and the oscilloscope. The terminal of the emitter has a connection with the ground via the 470Ω resistor in conjunction with the base terminal connected to the function generator output to the 6.8 nF capacitor and the voltage divider circuit. A parallel arrangement of 22 pF capacitor and 47 mH inductor had loopings between the 10v power supply and the transistor collector terminal. The same collector terminal was tapped and connected to the oscilloscope through a 6.8 nF capacitor. One channel of the oscilloscope was then used to set the voltage. Accuracy of the process had no consideration while doing the connection (Norman, 2013). The last part of the oscilloscope’s channel had its connection with the output. There was approximately no output from the oscilloscope. The input signal frequency increased while the output signal was noted together with the waveform generated. 2.2 Output data record The recording of the amplitudes of both received and transmitted signals of the peak voltage took place for all the frequencies being considered in a tabular manner. The results displayed on the oscilloscope were captured through a screen shot. The screen shots of the two frequencies were taken to assist in the drawing of the waveforms of the output signals. While doing so, a note was to be taken in considering the phase difference between the transmitted and the received signals (Manning, 2009). 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 signal 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 transmitted signal is at a peak voltage of 50mV while the received signal 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 produced ragged waveforms at a higher frequency (76.99 kHz). The crashing of waveform took place to make it appear smaller during the experiment. When the frequency came down to 66.09 kHz, the output waveform was smoothened into a clear larger sine wave. The waveform thus changes with a change in the frequency (Long and Mitnick, 2008). Discussion Resonant circuits can either be series or parallel resonant circuits. When working with such circuits or any electrical circuits, one has to be aware of potentially high voltages. A resonant circuit is similar to a tank circuit. The instance is that the circuit can store the energy it has taken from the power source in the capacitor and inductor and even produce a continuous AC waveform as an output. The circuit resonant frequency is number of times events occur per second as a set. The tuner circuit used in this report is like a parallel LC circuit where the current is minimum, and the impedance is maximum. Current, in this case, is the variable whereby at resonance, the two currents are 180 degrees out of phase with each other. Current acts inductively below resonance while it acts capacitive above resonance (Ingle, Bakland and Baumgartner, 2008). Resonant circuits have one important fact about how they operate: XL and XC only be equal to a single frequency known as the resonance frequency. The fact is the principle that enables tuned circuits in the radio receiver to select one particular frequency and reject all others. The resistance of the tuned circuit has limitations to the inherent resistance of the components, resistance of the coil, in particular. Studying tuned circuits is important as the circuit has various applications in almost every electronic device. It has applications in model airplanes controlled remotely and even the most sophisticated space satellite (Graham and McGowan, 2012). Charged particles in an antenna emit radiation like radio waves when they through acceleration. Electrons are forced into and out of the antenna by the AC voltage from the AFG. The AC voltage accelerates the electrons causing the electrons to emit radio waves that travel perpendicularly to the broadcasting antenna. It is thus advisable to set up the transmitting antenna to be in parallel to the receiving antenna (Antolovic, 2010). Conclusion Resonant circuits have got many applications in the television, communications, radio and other electronic fields throughout the Navy. Similarly, that by varying either the capacitor or inductor the resonance frequency of the circuit can be controlled. The resonant circuits can separate currents of certain frequencies from the other frequencies as they do tuning or station selection. A good selection of inductors, resistors, or capacitors produces a frequency selector or a filter network. Such network offers little opposition to one frequency while blocking or attenuating the other frequencies. Another filter network design can "pass" a band of frequencies and "reject" all the other frequencies. A filter circuit uses the combination of inductors, resistors and capacitors to either prevent or permit passage of a particular band of frequencies. Almost all electronic circuits require the use of filters in one way or another. A rectifier circuit forms the best example as the rectifier changes an alternating voltage to a direct current. However, the D.C. voltage is still fluctuating and pulsating as it is not pure. It only means that the signal still has an a.c. Component in addition to the dc component. A bypass capacitor is employed to shunt or bypass the unwanted AC components to the ground. Upon turning on the radio or television set, several events occur within the "receiver" before hearing the sound or seeing the picture being sent by the transmitting station. Several different signals reach the antenna of a radio receiver at the same time. The listener is forced to adjust the tuning dial on the radio receiver until a desired station for selection. A tuned circuit in a radio or TV receiver is the one that does the actual "selection" of the desired signal in the real sense and rejects the unwanted signals. The resonance phenomenon usually takes place whenever a tuned circuit has the characteristics of inductance and capacitance. Reference List Antolovic, D. 2010. Radiolocation in Ubiquitous Wireless Communication. New York: Springer. Graham, B. and McGowan, K. 2012. 101 Spy Gadgets for the Evil Genius. New York, NY: McGraw-Hill/TAB Electronics. Ingle, J., Bakland, L. and Baumgartner, J. 2008. Endodontics. Hamilton, Ontario: BC Decker. Long, J. and Mitnick, K. 2008. No Tech Hacking. Rockland, Mass.: Syngress. Manning, T. 2009. Microwave Radio Transmission Design Guide. Boston: Artech House. Norman, D. 2013. The Design of Everyday Things. New York: Basic Books. Progri, I. 2011. Geolocation of RF signals. New York: Springer. Serway, R. and Vuille, C.2007. Essentials of College Physics. Belmont, Calif.: Thomson- Brooks/Cole. Vendelin, G., Pavio, A. and Rohde, U. 2005. Microwave Circuit Design Using Linear and Nonlinear Techniques. Hoboken, NJ: Wiley. Read More