CIS Radio Intermediate Technical

1. CIS Radio Intermediate Technical

2. CIS Radio Intermediate Technical – Subjects covered:- Technical Basics Units & Symbols – Electrical Circuits – Conductors & Insulators – Power & Resistance – Ohms Law – Uses for resistors – Alternating Currents & Voltages – Different frequencies – Radio Frequencies – Wavelengths – Other radio users Transmitters A simple transmitter – Modulation Receivers A simple receiver – Detector Feeders & Antennas Feeders – Antennas (Dipole, ½ wave, 5/8th wave. Yagi and End Fed) – Polarisation – Matching Antennas – Antenna Tuning Unit – Standing Waves & SWR meters – Baluns – Dummy Loads Propagation Spreading out – Buildings – Range – The ionosphere – Frequency & time of day Electromagnetic Compatibility How is interference caused – What can be done to minimise interference – Earthing – Choice of antenna – Power and modes of transmission – Immunity – The neighbours – Other hazards Safety Considerations High Voltage – High current – Mains & earths – Protective Multiple Earthing – Accidents & emergencies – Antennas and feeders – Car batteries – Headphones – Other hazards

3. Units & Symbols

4. milli (written m) means thousandths of e.g. 10 mA = 10 thousandths of an Amp Kilo (written k) means thousands of e.g. 10kW = 10 thousand Watts e.g. 1kG = 1 thousand grams Mega (written M) means millions of e.g. 1M W = 1 million ohms Big and Small Units You should know:-

5. 100mA = ??? A 100mA = .1 A 10mA = ??? A 10mA = .010 A 10M W = ??? W 10M W = 10,000,000 W 1k W = ??? W 1k W = 1,000 W Converting between units

6. Potential Difference is measured in Volts e.g. Car Battery 12 Volts e.g. AA Cell 1.5 Volts e.g. PP3 Battery 9 Volts Voltage is a bit like the electrical form of “pressure” - the higher the voltage, the more current will flow through a circuit. Symbol is the letter V Volts

7. Electrical current is measured in Amps (short for Amperes) e.g. starter motor for car is about 100 Amps e.g. electric kettle is about 10 Amps Current is the quantity of electrons moving through a wire every second - think of the volume of water going through a pipe. Symbol is the letter I Amps

8. The current is a measure of how much electricity is flowing. The unit of measure is the amp The current is made up of millions of small particles called electrons which are electrically charged and move around the circuit carrying the electricity. These electrons need enough room to move and if a larger current is expected to flow a larger diameter wire is needed. The electrons get their energy from the supply or battery The electrons have more energy when they enter a device than when they leave it The potential difference across a device shows this difference in energy and is the energy being transferred to it often simply called the ‘voltage’

9. Potential Difference is measured in a unit called the Volt. If more volts are measured across a device it means the flow of electrons (current) is transferring more energy to that device. A 4 cell battery has a potential difference of 6V. It will give the electrons four times as much energy as a single cell (1.5V) and will cause the electrons to flow Quicker. Note: If we use mains supply the potential difference is 230V. Enough to cause serious injury or even kill you.

10. Electrical resistance is measured in Ohms Electrical resistance is the property of material to resist the movement of electrons. Think of plastics as having very high resistance, metals as having very low resistance. Symbol is the Greek letter omega W Ohms

11. Power is the amount of energy used each second. Power is measured in Watts Symbol is W Think of: Light bulbs 40W, 60W, 100W Kettle 2000W Power

12. Symbols You should be familiar with the following symbols -

13. Symbols

14. Resistor Coding Resistors are coded using colours - • Examples: • If the first band is green (5) the second digit is blue (6) and the third band is orange (3), the value of the resistor is 56000 ohm. Because 1000 Ohm = 1 K, we have 56k • B) red, red, yellow. So we have 2, 2, 0000 or 220.000 Ohm

15. Electrical Circuits

16. Electrical Circuits When you load a battery into an electronic device, you're not simply unleashing the electricity and sending it to do a task. Negatively charged electrons wish to travel to the positive portion of the battery and if they have to rev up your personal electric shaver along the way to get there, they'll do it. On a very simple level, it's much like water flowing down a stream and being forced to turn a water wheel to get from point A to point B.

17. Whether you are using a electrical mains or a battery to produce electricity, three things are always the same: 1. The source of electricity must have two terminals: a positive terminal and a negative terminal. 2. The source of electricity (whether it is a generator, battery or something else) will want to push electrons out of its negative terminal at a certain voltage. For example, one AA battery typically wants to push electrons out at 1.5 volts. 3. The electrons will need to flow from the negative terminal to the positive terminal through a copper wire or some other conductor. When there is a path that goes from the negative to the positive terminal, you have a circuit, and electrons can flow through the wire. A simple circuit with a variable resistor to increase or decrease the bulbs brightness

18. You can attach any type of load, such as a light bulb or motor, in the middle of the circuit. The source of electricity will power the load, and the load will perform whatever task it's designed to carry out, from spinning a shaft to generating light. Electrical circuits can get quite complex, but basically you always have the source of electricity (such as a battery), a load and two wires to carry electricity between the two. Electrons move from the source, through the load and back to the source. Moving electrons have energy. As the electrons move from one point to another, they can do work. In an incandescent light bulb, for example, the energy of the electrons is used to create heat, and the heat in turn creates light. In an electric motor, the energy in the electrons creates a magnetic field, and this field can interact with other magnets (through magnetic attraction and repulsion) to create motion This circuit shows a switch, motor and battery

19. An electric circuit is the name given to the way electrical devices are connected. By connecting a battery to a light bulb we make a circuit Consisting of the battery, connecting wires and the bulb

20. The battery provides the electrical energy. The electricity flows out of the positive side (+) along the connecting wire and into the bulb and back along a wire to the negative side (-). Electricity needs a complete circuit or path to flow round. Some electronic devices are very sensitive to which way around the battery is connected. The light bulb is a thin filament of wire in a glass bulb where all the air has been sucked out (a vacuum). If electricity is passed through the bulb the filament glows white hot and gives off light and heat. It does not matter which way the electricity flows through the bulb for it to work. It has no polarity. Care must be taken that the battery is of the correct voltage for the bulb or it will be either to dim or to bright and possibly blow.

21. Battery Circuits • A battery provides voltage but no current flows from it unless there is a circuit connecting the positive terminal and negative terminal together. • Battery “pushes” in a particular direction - not important for e.g. torch bulbs but usually very important for electronic devices.

22. Conductors & Insulators

23. The connecting wires we used to connect the battery to the bulb Is called a conductor and conducts electricity because the electrons can move freely. Metals are conductors. The wire should have a plastic sheath or covering. This is called an insulator and does not conduct electricity. Electrons cannot move in an insulator. Wood, rubber, glass and ceramics are also insulators but NOT if they get wet. Electricity may still be able to flow through any surface water and can still give you an electric shock. Be very careful in wet conditions

24. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them. "Conductor" implies that the outer electrons of the atoms are loosely bound and free to move through the material. Most atoms hold on to their electrons tightly and are insulators. In copper, the valence electrons are essentially free and strongly repel each other. Any external influence which moves one of them will cause a repulsion of other electrons which propagates, "domino fashion" through the conductor. Simply stated, most metals are good electrical conductors, most non-metals are not. Metals are also generally good heat conductors while non-metals are not.

25. Insulators Most solid materials are classified as insulators because they offer very large resistance to the flow of electric current. Metals are classified as conductors because their outer electrons are not tightly bound, but in most materials even the outermost electrons are so tightly bound that there is essentially zero electron flow through them with ordinary voltages. Some materials are particularly good insulators and can be characterized by their high resistance, plastic, wood, glass etc.

26. Power & Resistance

27. Potential Difference is measured in Volts e.g. Car Battery 12 Volts e.g. AA Cell 1.5 Volts e.g. PP3 Battery 9 Volts Voltage is a bit like the electrical form of “pressure” - the higher the voltage, the more current will flow through a circuit. Symbol is the letter V Volts

28. Electrical current is measured in Amps (short for Amperes) e.g. starter motor for car is about 100 Amps e.g. electric kettle is about 10 Amps Current is the quantity of electrons moving through a wire every second - think of the volume of water going through a pipe. Symbol is the letter I Amps

29. Electrical resistance is measured in Ohms Electrical resistance is the property of material to resist the movement of electrons. Think of plastics as having very high resistance, metals as having very low resistance. Symbol is the Greek letter omega W Ohms

30. Resistance Resistance is the measure of how difficult it is for electricity to flow. The symbol for resistance is Rand is measured in ohms (symbol Ω) In electrical terms a device that restricts the flow of current is called a resistor. How much difficulty it presents to the flow of the current is called its resistance. The higher the value the more resistance. If a voltage remained the same then higher resistance will mean a lower current flowing. Increasing the voltage would therefore increase the Current. This relationship is called V=IxR or Ohms Law

31. Power is the amount of energy used each second. Power is measured in Watts Symbol is W Think of: Light bulbs 40W, 60W, 100W Kettle 2000W Power

32. Ohms Law

33. V = I x R (so the voltage across a resistance is the product of the resistance and the current through it) Divide both sides of the top equation by I V / I = R (so the resistance of a circuit is given by the voltage across the circuit divided by the current through it) Or divide both sides of the top equation by R V / R = I (so the current through a circuit is given by the voltage across the circuit divided by the resistance) Ohms Law

34. Uses for Resistors

35. In electrical circuits it is often necessary to deliberately limit the flow of current. A resistor is used to insert some resistance into a circuit. A low value resistor will have little effect on the flow of current and the bulb will glow quite brightly. A higher value resistor will have a greater limiting effect on the current and the bulb will be much less bright. If the resistance is too high then the bulb may not glow at all.

36. Power is simply a measure of how quickly a device transfers the energy we deliver to it. Power is simply the voltage times the current. Power is measured in a unit called the watt The symbol is P So P = V x I (watts = volts x amps) A 1 watt light bulb transfers 1 unit of energy every second to heat and light POWER

37. Alternating Currents & Voltages

38. Alternating current, AC or a.c., keeps changing direction, first one way and then the other. AC is easier to generate and easier to change from one voltage to another. Your mains electricity is AC. The generator at the power station is a large coil of wire rotating around a powerful magnetic field. If we look at just one wire in the rotating coil, it is first going up through the field, then, half a turn later, coming down. Whilst the wire is going up the voltage and current generated has one polarity and moments later when its coming down the voltage and current are of opposite polarity.

39. The electricity produced by a bicycle dynamo is AC for the same reason. It is easy to produce and perfectly good for powering the light bulbs. The only problem is when the rider stops the lights go out unless there is a battery powered backup. The alternator in a car also produces AC but that is no use to charge the battery or run the many electronics like the radio. Special electronics are required to convert the AC into DC. That recharges the battery and powers all the electrical items including lights (which could use AC or DC) Alternating currents and voltages do not suddenly switch from one polarity to the other. They build up to a peak in one direction, then reduce back to zero before building up in the opposite direction. This smooth waveform is called a sine wave.

40. There are two features of AC or current that we need to know. • The size of the voltage • How often the cycles occur or the frequency. • Frequency is defined as the number of cycles occurring in 1 second. The unit of measurement is cycles per second or ‘Hertz’ Hz. • Domestic mains supply is 230 volts and 50Hz meaning there are 50 complete cycles in one second.

41. AC reverses its direction several/many times per second. Advantages: easier to generate (e.g. dynamo on bike) easier to step up and down to different voltages 1 cycle (one direction then the other direction) per second is called 1 Hz Mains supply is 50Hz Alternating Current AC

42. Direct Current DC Direct current or DC is the type of electricity that is produced by batteries, static, and lightning. A voltage is created, and possibly stored, until a circuit is completed. When it is, the current flows directly, in one direction. In the circuit, the current flows at a specific, constant voltage (this is oversimplified somewhat but good enough for our needs.) When you use a flashlight, pocket radio, portable CD player or virtually any other type of portable or battery-powered device, you are using direct current. Most DC circuits are relatively low in voltage. e.g. your car's battery is approximately 12 V. That's about as high a DC voltage as most people will ever use.

43. Different Frequencies

44. Sound is also an alternating signal carried by the movement of air. A sound of 50Hz is a very low note, as much felt as it is heard. Human hearing ranges from about 100Hz (a low note) to 15kHz (a very high note). For high quality music a full range of frequencies is desirable but for speech a much narrower range is sufficient. Usually 300Hz to 3kHz. Typical of a good telephone line. Electrical signals in the leads to a loudspeaker are alternating currents and voltages and many frequencies may be present at the same time, depending on the sounds. A clean whistle will be a single note and a single electrical frequency whilst music is likely to contain many notes and hence many frequencies.

45. Normal hearing (pressure waves in air) 100Hz - 15kHz (Audio Frequency - AF) Audio communication (electrical signals in wires etc) 300Hz - 3kHz HF, VHF, UHF radio signals are up to 1000MHz (Radio Frequency - RF) Some Typical Frequencies

46. Sine Wave Sine waves are produced by oscillators - think of a swinging pendulum.

47. Electromagnetic waves are waves consisting of vibrating electric and magnetic fields.  Various frequencies of theses waves are known as the Electromagnetic Spectrum

48. Radio Frequencies

49. Radio frequencies or RF are generated by feeding alternating electrical signals to an antenna. These frequencies are much higher than we can hear. While the whole of the electromagnetic wave spectrum covers a huge range of frequencies, radio waves themselves extend over a very large range as well. Again it is useful to be able to easily refer to different sections of the spectrum. To achieve this different designations are given to different areas. The frequencies that are covered are split into sections that vary by a factor of ten, e.g. from 3 MHz to 30 MHz. Each section is allocated a name such as high frequency and these areas are abbreviated to give terms like HF, VHF and so forth that are often used. Often talk is heard of VHF FM, or UHF television. The VHF and UHF refer to the areas of the radio spectrum where these transmissions take place. For ease of reference these frequencies are divided up into bands.

50. Waves with low frequencies or long wavelengths are known as radio waves and are produced by causing electrons to vibrate in an antenna. Molecular excitation produces microwaveand infrared waves which have little higher frequency than radio waves. A higher frequency of molecules make up the visibleand ultraviolet regions of the spectrum.  A very small portion of the electromagnetic spectrum is visible to the human eye.  It is the ultraviolet radiation in sunlight that tans or burns are skin. The next step of higher frequency waves are called X-rays. Lastly gamma rays are the highest frequency in the spectrum. All electromagnetic waves travel at the same speed in a vacuum.  This speed is called the speed of light and is designated by the letter C and = 299 792 458 m/s or 186000 miles a second