Transcript Technical Basics

East Kent Radio Society EKRS
1
Intermediate Course (3) Technical
Basics - 1
Components
Karl Davies
Electronic Components
2
 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
Electrical Units
3
Quantity
Voltage, V
Current, I
Resistance, R
Capacitance
Inductance
Power, P
Frequency, f
Wavelength, 
Unit
Volt
Amp
Ohm
Farad
Henry
Watt
Hertz
Metre
Symbol
V
aka Potential Difference
A

F
H
W
Hz
m
Unit Prefixes
4
Factor
trillionths
billionths
millionths
thousandths
thousands
millions
billions
SN
10-12
10-9
10-6
10-3
103
106
109
Examples:
25kV = 25000V
0.1uH = 100nH
Prefix
pico
nano
micro
milli
kilo
Mega
Giga
Symbol
p
n
 or u
m
k
M
G
1500mA = 1.5A
2.45GHz = 2450MHz
Ohms Law
5
V Volts
I Amps
R Ohms
Relates Voltage, V
Current, I Resistance, R
V=IxR
I=V/R
R=V/I
Power
6
P Watts
V Volts I Amps
Relates Power, P
Voltage, V Current, I
P=VxI
V=P/I
I=P/V
Cells & Batteries
7

 Batteries provide a source of DC power
 Note symbols for Single Cells or Battery Packs
 Cells store electrical energy by chemical means
Cell
 Primary Cells can only be used once.
 Secondary cells can be recharged. This reverses
the chemical reaction eg in Lead Acid, NiCd,
LiMH


+
Battery
 Beware of Leakage, Shorts esp on Lead-Acid
 Dispose of carefully
-

Resistors
8
 Fixed Resistors
traditionally identified by
Colour Code for Value &
Tolerance
Resistor
 Note that the modern BSI
Symbol is preferred to the
zigzag
•
Note all the symbols opposite
for the various forms
•
Check Wattage Rating
Preset
Resistor
No
Potentiometer
Variable
Resistor
Resistor Colour Code
9
 First two Bands
give Value Digits
 Third Band is the
Multiplier for
Factor of Ten
 Fourth Band is
Tolerance
 Example:-
12 x1000= 12k, 10%
Resistors in Series/Parallel
10
 Resistors in Series:-
Rtotal = R1+ R2+ R3 . . .
•
R1
R2
Resistors in Parallel:-
1/Rtotal = 1/R1+1/R2+1/R3 . . .
•
For Identical Resistors this simplifies to...
•
For Two Resistors:
Rtotal = R/2
R2
•
For Three Resistors:
Rtotal = R/3
R3
R1
R3
Inductors & Transformers
11
 Inductors are Coils which may be air or
ferrite cored
 Inductance is in Henries eg mH, nH, pH
 Inductance is proportional to number of
turns, diameter, core etc
Inductor
 Energy is stored in the magnetic field
 They pass DC but increasingly block AC at
higher frequencies
 Pairs of coils can be used to create
Transformers
Transformer
Iron-Cored
Inductor
Capacitors
12
 Capacitors are insulated plates, which
can store electric charge
Capacitor
 Larger plate areas, or smaller separation
will give higher capacitance
 Capacitance is in Farads eg uF, nF, pF
 They block DC but increasingly pass AC
at higher frequencies
Variable
Capacitor
 Beware Voltage rating and polarity of
Tantalum/Electrolytic versions
 Note all the symbols opposite
Polarised
Capacitor
Diodes
13
 Diodes are PN Junctions which only pass
current one way
 Diodes are a key item in PSUs where they rectify
AC into DC
Diode
LED
 Note Forward Current and Reverse Voltage
ratings, and small forward Voltage Drop
 LEDs - Light Emitting Diodes
 Variable Capacitance Diodes - use PN Jn
Capacitance
 Zener Diodes - have a precise Reverse Voltage
Varicap Diodes
Transistors
14
 Bipolar Transistors have NPN or PNP
junctions
c
b
 Middle section is the ‘Base’. A small
bias current can control a larger flow
between Collector and Emitter
 Current Flow is controlled
e
NPN Transistor
Electrostatically in FET devices
 Transistors can Amplify or Switch
d
- or Oscillate
 Integrated Circuits have arrays of
Transistors on a single chip
g
s
P-Channel
Field Effect Transistor (FET)
Miscellaneous
15
 Also need to recognise symbols for
Antenna
Switches, Grounds, Crystals etc, etc
Switch
SPST
Switch
DPST
Crystal
Loudspeaker
Fuse
Earth
Chassis
Lamp
Earphone
Microphone
Practical
16
 Recognise Resistors by Colour Code
 Measure Resistors in Series
 Measure Resistors in Parallel
 Learn to Recognise other Components
 Soldering - correctly without damage