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

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

Units Symbol Measured in Units Voltage V Volts Current I Amps A (Potential Difference) V Volts Current I Amps A Resistance R Ohms  Power P Watts W Frequency f Hertz Hz Wavelength  Metres m

Large & Small Units Meaning Decimal Prefix Example milli one thousandth 0.001 m 1mV = 0.001V 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 Lamp Resistor (or bulb) Resistor Antenna Earth Switch (s.p.s.t) Fuse

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

Voltage is sometimes referred to as “Potential Difference” 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

P V I Power Measured in Watts (W) Power = Voltage x Current P = V x I V = P / I I = P / V P V I

Resistance R 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) R Ω

V I R Ohm’s Law Voltage = Current x Resistance V = I x R I = V / R R = V / I V I R

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 Mains Frequency: 50Hz Audio Frequencies (AF): Human hearing: 100Hz to 15,000Hz Speech bandwidth: 300Hz to 3,000Hz Radio Frequencies (RF): HF: 3MHz to 30MHz VHF: 30MHz to 300MHz UHF: 300MHz to 3,000MHz

Summary Symbols and Units Power Resistance Frequency vs Wavelength 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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