An Amateur Licence primarily authorises the operation of an Amateur station

  • for self-training in radiocommunications,
  • intercommunications between Amateurs and
  • technical investigations into radiocommunications.

It is therefore very important, that the Foundation Licensee, understand basic electrical and electronics theory for the purpose of experimentation and safety in the field. This page is designed to provide the very basic knowledge required. I would encourage you to conduct further research and understanding using some of the detailed references provided.

Units of measurement

  • Current is a flow of electrical charge carriers, usually electrons or electron-deficient atoms. The common symbol for current is the uppercase letter I. The standard unit is the ampere, symbolised by A.
  • Voltage is the pressure from an electrical circuit’s power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light. In brief, voltage = pressure. The common symbol for voltage is the uppercase letter E (Electric potential difference, or Electromotive force). The standard unit is the volt, symbolised by V.
  • Resistance is a measure of the opposition to current flow in an electrical circuit. Resistance (R) is measured in ohms, symbolised by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm (1784-1854), a German physicist who studied the relationship between voltage, current and resistance.
  • Power is characterised by current or the flow of electric charge and voltage or the potential of charge to deliver energy. A given value of power can be produced by any combination of current and voltage values. The common symbol for power is the uppercase letter P. The standard unit is the watt, symbolised by W.

Ohms Law

What is Ohms law?

The basic formula’s for voltage and power are:

  • E (electromotive force) = I (current) * R (resistance)
  • P (power) = E (electromotive force) * I (current)

Measurement prefixes

The most common prefixes used in amateur radio consist of the following:

  • giga (G) 109 or 1,000,000,000
  • mega (M) 106 or 1,000,000
  • kilo (k) 103 or 1,000
  • milli (m) 10-3 or 0.001
  • micro (μ) 10-6 or 0.000001
  • nano (n) 10-9 or 0.000000001
  • pico (p) 10-12 or 0.000000000001

Examples

  • 22 kV = 22,000 V (22 kilo volts, 22 thousand volts)
  • 2 mV = 0.002 V (2 milli volts, 2 thousandths of a volt)
  • 22 kΩ = 22,000 Ω (22 kilo ohms, 22 thousand ohms)
  • 1 MΩ = 1,000,000 Ω (1 mega ohm, 1 million ohms)
  • 15 mA = 0.015 A (15 milli amps, 15 thousandths of an amp)
  • 120 μA = 0.000120 A (120 micro amps, 120 millionths of an amp)

Modulation

The meaning of AC and DC

  • Alternating Current (AC) means that the electrons flow in one direction stop and then flow in the other direction. Alternating current comes from an alternator and is the type of electricity that supplies mains power in Australia.
  • Direct Current (DC) means that the electrons flow in one direction, usually from a current source such as a battery.

Excessive voltage and incorrect polarity

Electronic circuits can be damaged by applying excessive voltage or incorrect polarity.

Audio and Radio Frequencies

Frequency (F)

  • Frequency is measured in Hertz abbreviation Hz
  • Hertz is the number of cycles an Alternating Current (AC) has per second
  • The 230 volt electricity supply in Australia is 50 Hz

Audible Frequency (AF)

  • Audible Frequency range 20 Hz to 20 kHz (top end lowers with age)
  • Voice frequency for radiotelephony 300 Hz to 3 kHz

Radio Frequencies (RF)

  • 300 kHz to 3 MHz Medium frequency (MF)
  • 3 MHz to 30 MHz High frequency (HF)
  • 30 MHz to 300 MHz Very high frequency (VHF)
  • 300 MHz to 3,000 MHz Ultra high frequency (UHF)

The Sine Wave

Sine waves are produced by oscillators and can be referred to by their:

  • Frequency – number of cycles per second, measured in Hz
  • Period – length of time taken for one complete cycle, measured in seconds
  • Wavelength – the distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave
  • Cycle – one cycle is shown on the above chart and represents the time taken for a single oscillation of voltage or current (note: the diagram shows the voltage and current 90 degrees out of phase)

Radio waves travel at the speed of light (C), which is 300 million metres per second.

Frequency and wavelength are inversely proportional to each other. The wave with the greatest frequency has the shortest wavelength. Twice the frequency means one-half the wavelength.

Conductors

  • Metal wires that join circuits are conductors
  • Most metals are good conductors in particular aluminium and copper
  • A small amount of electrical pressure (voltage) can make electrons move along a conductor

Insulators

  • Insulators do not allow electric current to pass easily
  • Insulators are plastics, dry wood, ceramic, porcelain, glass etc
  • Very large electrical pressure (very high voltage) must be applied to move electrons in insulators
  • These voltages usually damage the insulating material