chelmsford amateur radio society intermediate course (3) technical basics - 1 components

1Chelmsford Amateur Radio SocietyIntermediate Licence Course

Murray Niman G6JYB Slide Set 3: v1.2 3-May-2009(3) Technical Basics -1: Components

Chelmsford Amateur Radio Chelmsford Amateur Radio Society Society

Intermediate CourseIntermediate Course(3) Technical Basics - (3) Technical Basics -

11ComponentsComponents



Electronic Components

• Nature Amateur 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



• 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

Insulators, Conductors & Semiconductors



Electrical Units

Quantity Unit Symbol

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



Unit Prefixes

Factor SN Prefix Symbol

trillionths 10-12 pico p

billionths 10-9 nano n

millionths 10-6 micro or u

thousandths 10-3 milli m

thousands 103 kilo k

millions 106 Mega M

billions 109 Giga G

Examples: 25kV = 25000V 1500mA = 1.5A0.1uH = 100nH 2.45GHz = 2450MHz10pF = 0.01nF 0.5W = 500mW



Power

Relates Power, PVoltage, V Current, I

P=VxI V=P/I I=P/V

P Watts

V Volts I Amps

Recall from Foundation…



Ohms Law

Relates Voltage, V Current, I Resistance, R

V=IxR I=V/R R=V/I

V Volts

I Amps R Ohms

NB: Take care when quantities in formulas use unit prefixes



• 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

Cells & Batteries

Cell

Battery

+

-



• Fixed Resistors traditionally identified by Colour Code for Value & Tolerance

• Note that the modern BSI Symbol is preferred to the zigzag

Resistors

Resistor

VariableResistor

PresetResistor

Potentiometer

• Note all the symbols opposite for the various forms

• Check Wattage Rating

No



• First two Bands give Value Digits

• Third Band is the Multiplier for Factor of Ten

• Fourth Band is Tolerance

• Example:-

Resistor Colour Code

12 x1000= 12k, 10%



• Resistors in Series:-

Rtotal = R1+ R2+ R3 . . .

Resistors in Series/Parallel

• 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

R1 R2 R3

R1

R2

R3



• 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

Inductors & Transformers

Transformer

Air-Core Inductor

Iron-Cored Inductor



• 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

Capacitors

Capacitor

VariableCapacitor

PolarisedCapacitor



• 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

Diodes

Varicap Diodes

Diode LED



• 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

Transistors

c

e

b

Bipolar NPN Transistor

sg

d

P-Channel Field Effect Transistor (FET)



• 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

Transistor Gain

collector

emitter

base

NPN Transistor

IC

IB



• Also need to recognise symbols for Switches, Grounds, Crystals etc, etc

Miscellaneous

Earth EarphoneLampChassis

Crystal

Antenna

Microphone

LoudspeakerFuse

Switch SPST

Switch DPST



• 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

Practicals

chelmsford amateur radio society intermediate course (3) technical basics - 1 components

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