chelmsford amateur radio society advanced course 3 technical aspects part 1 primer n.
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Presentation Transcript
indices

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
logarithms numbers in standard form
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 & 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
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
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
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
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: 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
basic atomic structure

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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
slide11
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