1. Jonathon Matthews, Matthew Kirkham, MaximillionMaTech 1002- Studies in Media Technology Radio Lab reportDr. Andrew Clay.

2. Introduction In this report you will find the basic principles of how radio is transmitted more specifically though how AM (Amplitude Modulation) radio works. Covered under this will be transmitting and receiving and the differences with FM radio and AM radio. This will be followed by the results of a practical experiment undertook in which both the radio itself and an amplifier have been built and tested. AM only.

3. Principles of Radio Transmitting A radio wave carries information in the form of a signal; the information maybe on the wave itself embedded in the signal or it can be riding on the wave in a process called modulation. The two most used of modulation are AM (Amplitude Modulation) and FM(Frequency Modulation). AM modulation is older than FM and so you may get more sound distortion from it than you would from FM. However of these systems of modulation are analog meaning, they transmit in varying patterns of electrical signals . Sounds and images are converted into electrical signals then amplified, A carrier wave is then produced from the modulation which comes from the oscillator circuit in the transmitter. The carrier wave is then amplified, this is then sent to the antenna that then converts that signal into an electromagnetic wave.

4. Receiving An antenna on the receiving end of the broadcast i.e a home radio, car radio etc, pick up part of the signal being broadcast and send it to the receiver this then converts the electrical signal sends it to the amplifier either a speaker/headphones jack this is then converted into a sound wave and the original sounds sent cant be heard again. In the process a lot of changing happens to the original data being broadcast over the wave however at the end there is no change in the original data. However the sound quality will differentiate depending on the quality of the amplifier being used.

5. Example of Carrier modulation Here is an example of both FM modulation and AM modulation you can see from the image that AM is much looser than the FM signal meaning that less data can be sent at one time as it isn’t compressed. The reason for the difference in sound quality as a lower bitrate must be sent across the wave.

6. Practical Experiment Experiment 1 Apparatus. Iron rod Electrical tape Wire Circuit board Resistors Conduits Battery sockets Head phone jack. Objectives The main objectives for experiment 1 are to build the antenna then the receiving circuit using the kit provided and by following the handout.

7. Constructing the radio To make the antenna we had to wrap the wire around the metal rod. We were told that this would act as the receiver when it was soldered into the receiver circuit. Then we got the receiver circuit kit and then began to solder the resisters into the circuit. The resisters will stop the circuit from overloading with too much current (amps) and burning out all the components. Then after the resisters were in place then the conduits had to be soldered; into place as well. Then the battery had to be connected to the circuit is was really important that the positive and negative wires were in the right place in the circuit as if they weren’t the circuit would burn out and we would have to start all over again. Then the headphone socket was soldered onto the circuit board and now we had to test to see what and how many radio stations we could pick up.

8. Results During this phase of the experiment we could not find any stations or here any static so we changed the battery (twice), which lead to it being the circuits fault because when you touched the components underneath you had static. So we had a fault test done on the circuit by the lab technicians. They could not find anything wrong with the circuit, which led to the conclusion that it was one of the original components that had been at fault and was not the soldering, was narrowed down to be a resistor which had overloaded the circuit with too much current and fried the components in the circuit. So we had to start again but we kept the antenna as we were told that the antenna would be undamaged. So after building the circuit again we tested it again with multiple headphones and batteries. This still led to no results and no radio stations being picked up. So we again had the fault test done and the results were again inconclusive. So instead of remaking the circuit for a third time we were simply given a working station which we could pick up one station which was very weak, which we think was the BBC Asian network.

9. The Second Experiment Apparatus Speaker Battery connection Conduits LED light Objectives In this experiment we had to build the amplifier so thatwe could listen to the radio with out headphones.

10. Constructing the Amplifier Now that we had a working circuit we had to build the amplifying circuit so that we could listen to the radio with out headphones. To do this we first had to solder in the resistors just like in the receiver circuit. Then after the resistors were in place we then had to connect the audio amplifier that would be connected to the speaker. The we had to get a battery to power the circuit and the speaker. After connecting all the components together we had to then connect the recover circuit to the amplifier and see if the radio stations we picked up were amplified

11. Results After testing the amplifying circuit, the radio station that we could pick up on the receiving circuit we could no longer hear that radio station. We had a fault test done on the amplifier and the result came back to say that a resister had burned out. So we had to begin constructing the amplifying circuit again. When we had the amplifying circuit built up again we tested it and we picked up just the one radio station but we couldn’t tell if it was the one we had before as it was all distorted by the static.

12. Evaluation After successful completion of both the receiver circuit and the amplifier circuit, the necessary tests were undertook we found that resistors are very fragile as they can blow easily if not inserted in the correct places. If this were to happen on a larger circuit system then finding the problem would be increasingly difficult. Luckily as our circuit was fairly small this was not a big problem as we could rebuild a new circuit in around half an hour. When we had the radio running of the amplifier the sound crackled and was distorted with a more powerful speaker one of greater quality then the sound may not have been so bad this being so a greater power supply would have been needed to power the speaker and thus the entire circuit would need to be different to cope with the current. This being said without the need to change the amplifier the antenna could be changed to one that is more powerful so it could pick more stations and of a greater quality. As AM frequency is less commonly used these days in place of FM then the amount of stations being broadcast will be less hindering our results. If the experiment was done with similar equipment but built to pick up FM radio signals then the results would have been much better because the space around is saturated with FM radio waves.