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

Chelmsford Amateur Radio Society Advanced Course (3) Technical Aspects Part-1 - Primer. Decreasing value Increasing value 10 -12 10 -9 10 -6 10 -3 10 -2 10 0 10 2 10 3 10 6 10 9

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

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  1. Chelmsford Amateur Radio Society Advanced Course(3) Technical AspectsPart-1 - Primer

  2. Decreasing valueIncreasing value • 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

  3. 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.

  4. 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

  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

  6. 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

  7. 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

  8. 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

  9. 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

  10. - + 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

  11. 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

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