AMATEUR RADIO TRAINING Technical Basics Release: v1.21 hamtrain.co.uk

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

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

Large & Small Units MeaningDecimalPrefixExample millione thousandth0.001m1mV = 0.001V 111 watt kiloone thousand1,000k 2000  = 2k  Megaone million1,000,000M3MHz = 3,000,000Hz

Electrical Symbols CellBatteryMicrophoneSpeakerLamp (or bulb) ResistorAntennaEarthSwitch (s.p.s.t) Fuse

Conductors & Insulators Conductors: Copper Brass Silver Gold Insulators: Plastics Wood Rubber Glass Ceramics Safety Note: Water is a conductor! A conductor allows electrons to flow easily. An insulator does not.

Direct Current The battery provides DC Volts in a circuit Current flows in one direction, positive-to-negative, to light the lamp - Polarity for a filament bulb does not matter, but it does matter for other components Voltage is 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 / oppose the flow of current Measured in ohms Ω In this circuit, a resistor will cause the lamp to be dimmer (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 / I V R I

Frequency Frequency is represented as a ‘Sine Wave’, which can be generated by an oscillator. RF – Radio Frequency AF – Audio Frequency

Frequency & Wavelength Table

Frequencies Audio Frequencies (AF): Human hearing: 100Hz to 15,000Hz Speech bandwidth: 300Hz to 3,000Hz Mains Frequency: 50Hz Radio Frequencies (RF): 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

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