Transcript Technical Aspects-1 - Primer

Chelmsford Amateur Radio Society
Advanced Course
(3) Technical Aspects
Part-1 - Primer
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
1
Indices
You will be expected to handle unit prefixes from
pico to Giga, in multiples of 1000 or 103
Decreasing value
10-12
PICO
10-9
NANO
Chelmsford Amateur Radio Society
Advanced Licence Course
Increasing value
10-6
10-3
10-2
MICRO
MILLI
CENTI
100
BASIC
UNIT
Carl Thomson G3PEM
102
103
HECTO KILO
106
109
MEGA
GIGA
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
2
Logarithms & Numbers in
Standard Form
We can express numbers in many ways:
• 50,000 can equal 5 x 10,000 or in engineering as 5 x 104
• 50 Kiloohms can be written as 50 x 103
Logarithms are an aid to calculation:
Any positive number can be expressed as a power of 10.
• Example: 1000 = 103
These powers of 10 are called logarithms to the base 10. That is:
• NUMBER = 10 Logarithm
We use tables or a calculator to find the logarithm.
The reverse of this is the ANTILOG - also by tables/calculators.
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
3
Squares & Roots
SQUARES
•
When a number is multiplied by itself the result is called the square.
– Example:
•
The Square of 9 is 9 x 9 = 81.
Normally we express this as 92 - saves writing 9 x 9 all the time.
SQUARE ROOTS
•
The square root is a number whose square equals the given number.
– Example:
•
52 = 25 , the square root of 25 is therefore 5
The sign  is used to denote square root so we can write 25 = 5
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
4
Algebra
You will need some knowledge of how to move simple
formulas around to derive the unknown term.
P = V2 / R
R
=
V/I
C
=
KA/d
XL
=
2πFL
XC
=
1/ 2 π F C
F
=
1 / 2 π  LC
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
P = I2 R
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
5
Decibels
• Power ratios in Decibels are 10xLog(P1/P2) - Half power is 3dB
• Voltage or Current ratios 20xLog(V1/V2) - Half voltage or current is 6dB
• Decibels are sometimes quoted relative to a reference quantity
dBW = Decibels relative to a reference of 1 Watt - as in the Schedule
dBm = Decibels relative to reference power of 1mW
dBi = Antenna gain relative to a perfect ISOTROPIC antenna.
dBd = Antenna gain performance expressed relative to a DIPOLE
• Remember dB ratios based on ±3, 6, 9, 12, 15 and 10, 20, 30dB
Example: 25W = (20-6)dBW = 14dBW
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
6
Matter
FUNDAMENTALS
• Matter exists as Solid, Liquid or Gas
• The effects of an electric current can be; magnetic, heating, chemical
• Conversely electric current are produced from the expenditure of;
magnetic, heat, or chemical energy.
COMPOUNDS AND ELEMENTS
• Most objects are a Compound of two or more simple substances.
• Simple substances are those that cannot be broken down further
– Pure Hydrogen contains only Hydrogen these are called ELEMENTS
• Water is a compound of two elements Hydrogen and Oxygen - H2O
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
7
Molecules & Atoms
ATOMS
• Atoms are the name given to the smallest particle of an element
• They cannot exist alone for any length of time
• They will combine with other atoms to form a molecule
MOLECULES
• A Molecule is the smallest possible particle of a substance, without
breaking it into its chemical parts or losing its identity
• Molecules are in a continual state of movement
• Increase in temperature will cause them to vibrate/move more
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
8
Atoms: Electrons, Protons
& Neutrons
Atoms are constructed from particles termed Electrons, Protons, Neutrons
• ELECTRONS carry a NEGATIVE charge which is 1.6 x 10-19 COULOMBS
• This is the fundamental unit of Electricity
• The MASS of an electron is 9.1 x 10-31 kg
• PROTONS carry a POSITIVE charge which is also 1.6 x 10-19 COULOMBS,
the same as an electron. The MASS is ~1840 times greater than an electron
• NEUTRONS carry no charge. Their mass is about the same as a proton
• In a normal state every atom has equal numbers of electrons and protons
both have equal charge so the atom is electrically neutral
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
9
Basic Atomic Structure
• The simplest atom, hydrogen has one proton around which a single
electron revolves in a fixed orbit, like the earth-moon relationship.
• The structure of other atoms is more complex like our solar system.
• In a metal, the outermost electrons can drift into orbits of adjacent
atoms. This movement of electrons FROM NEGATIVE TO POSITIVE
creates the electric current flow when a voltage is present
-
+
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
10
Ions
• If an electron is detached from an atom it leaves the atom with a net
positive charge. Or, if a neutral atom acquires an additional orbital
electron the atom assumes a negative charge
• Atoms or groups of atoms which assume net electrical charge are Ions
• Positive Ions are deficient of one or more electrons
• Negative Ions possess one or more extra electrons
CONDUCTORS AND INSULATORS
• Materials which readily permit flow of electrons are conductors
• Materials with no appreciable electron drift are insulators
Chelmsford Amateur Radio Society
Advanced Licence Course
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
11