Tech 1002 Studies In Media Technology Radio Lab Online Report

TECH 1002 STUDIES IN MEDIA TECHNOLOGYRADIO LAB REPORT

Michael Sharman

Sian Kayleigh O’Brien

Rinqueche Manilal

Emma Nguyen

AM Radio Receiver and Amplifier Project

Aims and Objectives We intend to build a radio and amplifier and

test them to see what radio stations we can pick up while explaining our results, how we got them and how the radio works.

Objectives: Create a full working radio. Create a full working amplifier. Record our results accurately. Explain our results.

AM Radio Receiver and Amplifier Project Equipment AM Radio Receiver: Soldering equipment set. Printed circuit board. Components -IC MK484, transistor BC548B, 150pF

variable tuning capacitor, ferrite rod, 2.5m of 0.315mm enamelled copper wire, two 100K resistors (brown, black, yellow), two 1K resistors (brown, black, red), one 270R resistor (red, violet, brown), Ultra-miniature slide switch, two 100nF capacitors, one10nF capacitor, one 47uF capacitor, headphone socket, AA battery holder.

AM Radio Receiver and Amplifier Project Equipment Amplifier: Soldering equipment set. Printed circuit board. Components: IC TBA 820M, three 1K resistors R1, R2, R3

(brown, black, red), two 470R resistors R4,R6 (yellow, violet, brown) and one 1R resistor R5(brown, black, gold). Two 330uF electrolytic capacitors C3, C6.One 10uF electrolytic capacitorC1. One 150pF ceramic capacitor C2. One 100nFpolyester capacitor C4. One 47nF polyester capacitor C5. One 8 Ohm speaker. 100mm of speaker cable. One slide switch. One PP3 battery snap. One 3.5mmplug to plug cable. One 3.5mmstereo jack socket.

Method

AM Radio Receiver: We started by making the aerial where we wrapped a piece of

cardboard around the metal rod and taped it into place. We then wound the copper wire carefully around the rod 55 times. It was important that the copper wire did not overlap because the finished coil aerial will be used to receive the frequency of radio waves.

We then taped the wire down at the ends and filed them so that the metal enamel came off. Next the following items were soldered into place on the circuit board – resistors, smaller capacitors, transistor BC548B, MK484 radio IC and the variable tuning capacitor (150pF).

The variable tuning capacitor (150pF) selects the exact tuning frequency of the radio wave you want to listen to, while ignoring numerous other radio waves in the air. This is done by changing the value of the capacitor in the tuning circuit, therefore changing the frequency. This is all part of the Tuning section of the circuit.

Method The IC MK484 diode lets the current flow through in one

direction but not the other, in turn clipping off part of the wave, as seen in FIGURE 1. This turns the radio signal received from the aerial back into an audio signal to then be sent to the transistor. This process is called demodulation.

Figure 1 – Showing how a diode demodulates a radio signal into an audio signal

Method We then attached the connecting wires to the headphones socket

and then we attached the headphones socket to the circuit board. The last thing to do was to attach the AA battery holder to the circuit board.

The transistor BC548B that we soldered on earlier is made up of 3 parts: a base, a collector and an emitter. The base acts like a gate controlling the current flow from the battery, the collector collects the electrical power from the battery and the emitter sends the supply on to the headphones socket or speaker as shown in figure 2. This is described as the amplifier section of the circuit.

Figure 2 - diagram of the three parts that make up a transistor

Method Audio Amplifier: We soldered everything into place on the circuit board, we then placed

TBA820M into the soldered on IC socket, attached the battery and tested the circuit. Amplifier is an important component of the radio, as it helps boost the small signals and sound, that can’t be read or heard. Once the amplifier is in use, the small signals can be read and heard easily. The better the sound wave, the better quality of the sound will be coming out of the speaker

The sound waves will be captured through the aerial and then once the waves are captured the signals are going to get converted to electrical signals. The electrical signals are then amplified and converted, by the amplifier to output the sound through the radio speaker, which is a recreated sound wave.

The key component of the amplifier is IC, which stands for Integrated Component .The component helps the amplifier to create a better sound quality, also needs a battery, because it provides electrical energy, so that the electrical signal travels through the wires and makes the speaker work.

Results

Radio: At first, the radio didn’t pick up anything. After modifications were made to the circuit we got only one headphone working. Then after a few more modifications we picked up Asian Network and Sabras Radio. Asian Network was received clearly where as Sabras Radio was quite distorted.

Amplifier: At first, it did not amplify any sound. After some modifications, it was successful.

Explanations of Results Radio: The reason for our radio not working at first was due to

the enamelled Copper wire not being filed down enough. We then realised there were a few problems with the soldering. For instance, on the switch there were not three distinct gaps between the soldering points, the headphones socket was not soldered enough, and the tuning capacitor wasn’t soldered correctly.

The reason for the two stations being picked up was because they were in our region of Leicestershire. The stations are also based in the city of Leicester which is why they could be picked up compared to other stations as their signal was stronger.

Amplifier: It did not work at first because the connection between the wire from the circuit and the speaker was not soldered properly. Once corrected, the sound was amplified accurately.

AM Transmission Demonstration Aims and Objectives The aim of the demonstration was to

show a carrier waves amplitude modulation with an audio information signal. The objective was to show the theory of how amplitude modulation (AM) is used for radio transmission.

AM Transmission Demonstration Equipment Oscilloscope - tuner Function generator Wire aerial AM radio receiver

Method

During the demonstration, the carrier wave was set to 600KH so that it can be transmitted and received by the AM radio receiver. An audio signal was then added to the carrier wave, set to 500 hertz which generated 2 signals. The amplitude of the audio signal was then altered.

Results

When the amplitude of the audio signal was altered, the audio signal was picked up by the AM radio and a sound was heard.

Explanation of Results

The sound was heard because the peaks of the waves (amplitude) of the audio signal were made bigger.

Modulation is when the programme signal you want to send is added to a carrier wave so that it can be transmitted and received by another radio with an aerial or antenna. Frequency modulation describes a program signal that when added to a carrier wave, creates fluctuations in the frequency. Amplitude modulation is when the size of the peaks in a carrier wave (the amplitude) is made bigger or smaller, creating another way of sending a radio signal. Frequency modulation is how FM radio is transmitted and while AM is transmitted using amplitude modulation.

Explanation of Results

A good example of how the two types of modulation work differently is described on explainstuff.com:

 1'Suppose I'm on a rowboat in the ocean pretending to be a radio transmitter and you're on the shore pretending to be a radio receiver. Let's say I want to send a distress signal to you. I could rock the boat up and down quickly in the water to send big waves to you. If there are already waves travelling past my boat, from the distant ocean to the shore, my movements are going to make those existing waves much bigger. In other words, I will be using the waves passing by as a carrier to send my signal and, because I'll be changing the height of the waves, I'll be transmitting my signal by amplitude modulation. Alternatively, instead of moving my boat up and down, I could put my hand in the water and move it quickly back and forth. Now I'll make the waves travel more quickly—increasing their frequency. So, in this case, my signal will travel to you by frequency modulation.'

Conclusion During the radio labs we successful created and a

radio and amplifier which could pick up 2 radio stations, one clearer than the other. The reason for the two stations being picked up was because they were in our region of Leicestershire. We have also established the technical aspects of the radio and how each individual part works from changing a radio carrier wave into an audio signal (demodulation), and then amplifying the signal so it is detectable by the human ear. We also learnt how a AM Transmission was broadcasted using a various range of equipment, and how it was picked up by a receiver.

Images of us working on Radio

List of Figures

Figure 1 – Showing how a diode demodulates a radio signal into an audio signal

Figure 2 - diagram of the three parts that make up a transistor

Bibliography

General explanation of all aspects of a radio 1(direct quote) http://www.explainthatstuff.com/radio.html Resistors explanations http://www.physlink.com/Education/AskExperts/ae430.cfm Radio http://www.electronics-radio.com/articles/radio/index.ph Radio waves and communication http://www.ofcom.org.uk/sitefinder/glossary/how/ http://science.hq.nasa.gov/kids/imagers/ems/radio.html http://www.wisegeek.com/what-are-radio-waves.htm http://en.wikipedia.org/wiki/Radio_waves http://www.ofcom.org.uk/sitefinder/glossary/how/ AM Broadcasting Wikipedia. 25 January 2010. AM Broadcasting.[Online] Available from: http://en.wikipedia.org/wiki/AM_radio Modulation and Amplitude Modulation Amplitude Modulation. [online]. Available from: http://en.wikipedia.org/wiki/Amplitude_modulation FM Broadcasting Wikipedia. 25 January 2010. FM Broadcasting.[Online] Available from: http://en.wikipedia.org/wiki/FM_broadcasting Frequency Finder http://frequencyfinder.org.uk/ How Radio Works How Stuff Works. How Radio Works. [online]. Available from:http://electronics.howstuffworks.com/radio3.html Modulation http://en.wikipedia.org/wiki/Modulation Images : Taken by ourselves