AMATEUR RADIO TRAINING

Technical Basics

v1.12 © essexham.co.uk

TECHNICAL BASICS

• Units, Symbols and Circuits• Conductors & Insulators• Formulas• Frequency / Wavelength

UnitsSymbol Measured in Units

Voltage(Potential Difference)

V Volts V

Current I Amps A

Resistance R Ohms

Power W Watts W

Frequency f Hertz Hz

Wavelength Metres m

Large & Small UnitsMeaning Decimal Prefix Example

milli one thousandth 0.001 m 1mV = 0.001V

1 1 1 watt

kilo One thousand 1,000 k 2000 = 2k

mega One million 1,000,000 M 3MHz = 3,000,000Hz

Electrical Symbols

Cell Battery Microphone Speaker Bulb

Resistor Antenna Earth Switch Fuse

Conductors & Insulators

Conductors:

• Copper

• Brass

• Silver

• Gold

Insulators:

• Wood

• Rubber

• Glass

• Ceramics

Safety Note: Water is a conductor!

Direct Current

The battery provides DC Volts

Current flows in one direction, positive-to-negative, to light the bulb

Note: Voltage sometimes referred to as “Potential Difference”

Alternating Current

AC is easier to generate and distribute

AC constantly changes from positive to negative

UK Mains Voltage ~ 230 Volts ; 50 Hz (alternates 50 times per second)

+

-Time

Power

Measured in Watts (W)

Power = Voltage x Current

• P = V x I

• V = P / I

• I = P / V

P

IV

Resistance• Resistors limit the flow of

current

• Measured in ohms Ω

• In this circuit, a resistor will cause the bulb to be less bright (low resistance), or to not light at all (high resistance)

Ω R

Ohm’s Law

Voltage = Current x Resistance

• V = I x R

• I = V / R

• R = V / IV

RI

Frequency & Wavelength Table

Frequencies

Audio Frequencies:

• Human hearing: 100Hz to 15,000Hz

• Speech bandwidth: 300Hz to 3,000Hz

Mains Frequency:

• 50Hz

Radio Frequencies:

• HF: 3MHz to 30MHz

• VHF: 30MHz to 300MHz

• UHF: 300MHz to 3,000MHz

Summary• Symbols and Units

• Learn the symbols and prefixes (e.g: mW, kHz, M)

• Recognise the symbols (resistor, cell, speaker, microphone, etc)

• Power

• Alternating vs Direct

• Power (watts) = Volts x Current

• Resistance

• Ohm’s law: Volts = Current x Resistance

• Frequency vs Wavelength

• As Frequency rises, wavelength reduces

TECHNICAL BASICS

Any questions?

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