Chelmsford Amateur Radio Society Intermediate Course (3) Technical Basics - 1 Components

1. Chelmsford Amateur Radio Society Intermediate Course(3) Technical Basics - 1Components

2. Electronic Components • NatureAmateur Radio applies Electronics to Wireless Communication • Items Common Electronic Components Include: • Resistors, inc Colour code • Capacitors, Inductors, Resonant Circuits • Diodes & LEDs • Transistors • Switches, Fuses, Connectors • The Intermediate Licence expects you to be able to recognise components, their circuit symbols, and to build and test simple circuits

3. Insulators, Conductors & Semiconductors • Conductors permit the flow of electric current • Examples: Copper, Brass etc - (ie mainly metals) • Metallic Conductors permit electrons to flow easily, but beware of poor/oxidised connections (eg on Aluminium, Steel) • Insulators don’t permit electron flow and exhibit high resistance. • Examples: Plastics, wood, rubber, glass, ceramics • Water may conduct (esp. when impure) and that wet insulators therefore may conduct on their surface - a risk for outdoor work • Semiconductors (Silicon, Germanium etc) barely conduct unless small dopants are added to create P or N-type materials

4. Electrical Units QuantityUnitSymbol Voltage, V Volt V aka Potential Difference Current, I Amp A Resistance, R Ohm  Capacitance Farad F Inductance Henry H Power, P Watt W Frequency, f Hertz Hz Wavelength,  Metre m

5. Unit Prefixes FactorSNPrefixSymbol trillionths 10-12pico p billionths 10-9nano n millionths 10-6micro  or u thousandths 10-3 milli m thousands 103 kilo k millions 106 Mega M billions109 Giga G Examples: 25kV = 25000V 1500mA = 1.5A 0.1uH = 100nH 2.45GHz = 2450MHz 10pF = 0.01nF 0.5W = 500mW

6. P Watts V Volts I Amps Power Recall from Foundation… Relates Power, P Voltage, V Current, I P=VxI V=P/I I=P/V

7. V Volts I Amps R Ohms Ohms Law NB: Take care when quantities in formulas use unit prefixes Relates Voltage, V Current, I Resistance, R V=IxR I=V/R R=V/I

8.  Cell   + Battery -  Cells & Batteries • Batteries provide a source of DC power • Note symbols for Single Cells or Battery Packs • Cells store electrical energy by chemical means • Primary Cells can only be used once. • Secondary cells can be recharged. This reverses the chemical reaction eg in Lead Acid, NiCd, LiMH • Beware of Leakage, Shorts esp on Lead-Acid • Dispose of carefully

9. Preset Resistor Resistor No Potentiometer Variable Resistor Resistors • Fixed Resistors traditionally identified by Colour Code for Value & Tolerance • Note that the modern BSI Symbol is preferred to the zigzag • Note all the symbols opposite for the various forms • Check Wattage Rating

10. 12 x1000= 12k, 10% Resistor Colour Code • First two Bands give Value Digits • Third Band is the Multiplier for Factor of Ten • Fourth Band is Tolerance • Example:-

11. R1 R2 R3 R1 R2 R3 Resistors in Series/Parallel • Resistors in Series:- Rtotal = R1+ R2+ R3 . . . • Resistors in Parallel:- • 1/Rtotal = 1/R1+1/R2+1/R3 . . . • For Identical Resistors this simplifies to... • For Two Resistors: Rtotal = R/2 • For Three Resistors: Rtotal = R/3

12. Air-Core Inductor Iron-Cored Inductor Transformer Inductors & Transformers • Inductors are Coils of Wire which may have air or ferrite/iron cores • Energy is stored in the magnetic field • Inductance is proportional to number of turns, diameter, core etc • Inductance is in Henries eg mH, nH, pH • Inductors pass DC but increasingly block AC at higher frequencies • Pairs of coils can be used to create Transformers – for PSUs, RF circuits etc

13. Capacitor Variable Capacitor Polarised Capacitor Capacitors • Capacitors are insulated plates, which can store electric charge and energy in the electric field • Larger plate areas, the nature of materials between the plates or smaller plate separation will give higher capacitance • Capacitance is in Farads eg uF, nF, pF • Capacitors block DC but increasingly pass AC at higher frequencies • Beware Voltage rating and polarity of Tantalum/Electrolytic versions • Note all the symbols opposite

14. Diode LED Varicap Diodes Diodes • Diodes are PN Junctions of semiconductor materials which only pass current one way • Diodes are a key item in PSUs where they rectify AC into DC • Note Forward Current and Reverse Voltage ratings, and a small forward bias Voltage Drop • LEDs - Light Emitting Diodes • Variable Capacitance Diodes – exploits PN Junction Capacitance when reverse biased • Zener Diodes - have a precise Reverse Voltage

15. c b e Bipolar NPN Transistor d g s P-Channel Field Effect Transistor (FET) Transistors • Bipolar Transistors are NPN or PNP junctions of semiconductor material • Middle section is the ‘Base’. A small bias current can control a larger flow between Collector and Emitter • In FET devices current flow between Drain and Source is controlled Electrostatically by the Gate voltage • Depending on the circuit, Transistors can Amplify or Switch - or Oscillate • Integrated Circuits have arrays of many Transistors on a single chip

16. IC collector base IB emitter NPN Transistor Transistor Gain • Current flow in the Collector (IC) to the Emitter can be controlled by a smaller bias current in the Base, IB • If levels are set correctly, small variations in base current are amplified at the output • Current Gain or ‘Beta’ is the ratio of IC/IB ß = IC / IB or, IC = ß x IB • For example, a base current of 5mA in a device with Beta=50 controls an IC of 0.25A

17. Antenna Switch SPST Switch DPST Loudspeaker Crystal Fuse Earth Chassis Lamp Earphone Microphone Miscellaneous • Also need to recognise symbols for Switches, Grounds, Crystals etc, etc

18. Practicals • Recognise Resistors by Colour Code • Measure Resistors in Series • Measure Resistors in Parallel • Learn to Recognise other Components • Soldering - correctly without damage • Build and test board with resistors and transistor