# Aslide1-Technical-Aspects-1

```Chelmsford Amateur Radio Society
(3) Technical Aspects
Part-1 - Primer
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
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 &amp; 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.
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
3
Squares &amp; 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
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
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 &plusmn;3, 6, 9, 12, 15 and 10, 20, 30dB
Example: 25W = (20-6)dBW = 14dBW
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
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
7
Molecules &amp; 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
Carl Thomson G3PEM
Slide Set 1: v1.1, 8-Feb-2013
(3) Technical Aspects - Primer
8
Atoms: Electrons, Protons
&amp; 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
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
-
+
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