AMATEUR RADIO TRAINING Technical Basics v1.12 © essexham.co.uk

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

Units SymbolMeasured inUnits Voltage (Potential Difference) VVoltsV CurrentIAmpsA ResistanceROhms PowerWWattsW FrequencyfHertzHz Wavelength Metresm

Large & Small Units MeaningDecimalPrefixExample millione thousandth0.001m1mV = 0.001V 111 watt kiloOne thousand1,000k megaOne million1,000,000M3MHz = 3,000,000Hz

Electrical Symbols CellBatteryMicrophoneSpeakerBulb ResistorAntennaEarthSwitchFuse

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 I V

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

Ohms Law Voltage = Current x Resistance V = I x R I = V / R R = V / I V R I

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 Ohms law: Volts = Current x Resistance Frequency vs Wavelength As Frequency rises, wavelength reduces

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