1 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Chelmsford Amateur Radio Society M3 Foundation Course (3) Technical Basics

2 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Electrical Units QuantityUnitSymbol Voltage, VVoltV Current, IAmpA Resistance, ROhm  Power, PWattW Frequency, fHertzHz Wavelength, Metrem Note-1: Resistance is the opposition to current flow Note-2: Voltage is sometimes referred to as Potential Difference

3 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Unit Prefixes FactorPrefixSymbol millionthsmicro  or u thousandths millim thousandskilok millionsMegaM Examples: 4.7k  =  4700  1500mA = 1.5A 0.6MHz = 600kHz

4 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Power Relates Power, PVoltage, VCurrent, I P=V x IV=P/II=P/V P Watts V Volts I Amps

5 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Ohms Law Relates Voltage, VCurrent, IResistance, R V=I x RI=V/RR=V/I V Volts I Amps R Ohms

6 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Batteries provide a source of DC power DC- Direct Current, flows in a single direction DC & AC Power   AC - Alternating Current AC is easier to generate and transform Mains is 50Hz AC. Radio uses High Frequency AC Simple items such as Bulbs work with AC and DC, but many electronic components are sensitive to the direction of current

7 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics In air the velocity, v of radio waves is a constant ( ~3x10 8 m/s) So if the frequency increases, the wavelength decreases, and vice versa, determined by: v = f x A 1MHz to 1000MHz conversion chart, and frequency allocation table is available Frequency & Wavelength v m/s f Hertz metres v f

8 Chelmsford Amateur Radio Society M3 Foundation Licence Course Murray Niman G6JYB Slide Set 3 (3) Technical Basics Also need to recognise symbols for Switches, Earths, Crystals etc, etc Circuit Symbols Earth Lamp Crystal Antenna Microphone Loudspeaker Fuse Switch SPST Resistor   Battery + -   Cell