Chelmsford Amateur Radio Society Advanced Course (3) Technical Aspects Part-1 - Primer

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# Chelmsford Amateur Radio Society Advanced Course (3) Technical Aspects Part-1 - Primer - PowerPoint PPT Presentation

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## Chelmsford Amateur Radio Society Advanced Course (3) Technical Aspects Part-1 - Primer

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• 10-12 10-9 10-6 10-3 10-2 100 102 103 106 109
• PICO NANO MICRO MILLI CENTI BASIC HECTO KILO MEGA GIGA
• UNIT
Indices
• You will be expected to handle unit prefixes from
• pico to Giga, in multiples of 1000 or 103
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.
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
Algebra

You will need some knowledge of how to move simple formulas around to derive the unknown term.

R = V / I P = V2 / R P = I2 R

C = K A / d

XL = 2 π F L

XC = 1/ 2 π F C

F = 1 / 2 π  LC

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
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
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
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

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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
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