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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