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Transcript
Radio Station Setup and Electrical Principles Covers sections: T4A-T5D Seth Price, N3MRA February 20, 2016 Week 4 Outline • • • • • • 4.1 4.2 4.3 4.4 4.5 4.6 Week 4 Station Setup Operating Controls Electronic Principles Ohm’s Law Power Calculations Storing Energy Typical Base Radio Station (4.1) • Transceiver – Microphone – Key – Terminal Node Controller (TNC) • Antenna – Antenna Tuner • Power Supply (12V) • Speaker – Headphones • Amplifier* • Computer* Week 4 Mobile Operation (4.1, 4.2) • Power (12V Car Battery) – Fused power line – Connect negative power line to battery • Antenna – Magnet mounts – Permanent mounts • Reducing noise – Alternator produces a high pitch whine – Noise blanker can help – Control computer can cause noise Week 4 www.ke4nyv.com Typical VHF Radio (4.2) Week 4 VHF/UHF Operation (4.2) • VFO Knob: Variable Frequency Oscillator knob, selects frequency • Squelch: filters noise below a certain volume • Memory functions: can save band edges, favorite frequencies, repeater offsets, etc • Power setting: typically toggles between several settings (5W, 10W, 50W) • DTMF Mic: dual tone, multi frequency microphone, can do lots of things from mic Week 4 Typical HF Radio (4.2) Week 4 HF Transceiver Operations (4.2) • S Meter: multifunction meter that shows signal strength • Audio gain: volume knob • Squelch: filters noise below a certain volume • Memory functions: can save band edges, favorite frequencies, etc • Mode selection: choose FM, AM, SSB, etc. Week 4 HF Transceiver Operations (4.2) • Mic Gain: adjusts amplification of microphone – If set too high, your signal will be distorted • VFO Knob: Variable Frequency Oscillator knob, selects frequency • RIT: Receiver Incremental Tuning, the receiver and transmitter are on different frequencies – Sometimes referred to as running a “split” • Output Power: 5W-100W, typically Week 4 HF Transceiver Operations • Notch Filter: Used for removing carriers from the pass band • Automatic Level Control (ALC): Reduces distortion due to excess drive “flat-topping” (too much mic gain, too close to mic, etc.) • Intermediate Frequency (IF) Shift: Removes interference from nearby stations • Attenuator: Reduces signal strength from really strong signals Week 4 HF Transceiver Operations • Speech Processing: Voice signal is compressed, putting more power into the important tones – Better intelligibility during poor band conditions – If improperly adjusted, signal can splatter, become distorted or pick up background noise • Something Week 4 Electrical Definitions (4.3) • Voltage: electromotive force (EMF) that causes electron flow, measured in Volts (V) • Current: the flow of electrons in a circuit, measured in Amperes, or Amps (A) • Resistance: measure of electron flow restriction, measured in Ohms (omega) • Power: rate at which electrical energy is used, measured in Watts (W) • Conductor: low resistance, electrons flow easily (metal) • Insulator: high resistance, electrons have trouble flowing (ceramic, wood, plastic, etc). Week 4 Power and Ground (4.2) • Proper power supplies are: – Regulated (filtered) to allow only certain frequencies and amplitudes through – 12V is typical for amateur radio • Proper grounds are: – Metal connections to ground (chassis, flat strap) – Connections are typically green Week 4 Current (4.3) • Direct Current (DC) – Current flows only one direction – Example: Battery • Alternating Current (AC) – Current switches directions (measured in Hertz, Hz) – Example: Wall power (US: 117V, 60Hz) Week 4 Unit Conversions (4.3) • How many millivolts are in one volt? • How many Megahertz are in one kilohertz? • How many picofarads are in one Farad? Week 4 Common Schematic Symbols (4.3) Name Symbol Units Resistor Ohms Potentiometer Ohms Voltage Supply Volts Inductor Henries Capacitor Farads LED n/a Week 4 Measuring Voltage/Current (4.3) • Voltmeters are connected in parallel – This measures voltage across a device – Voltmeters try to have infinite resistance • Ammeters are connected in series – This measures current through a device – Ammeters try to model zero resistance Week 4 Resistor Color Codes (4.3) • Used to specify value and tolerance of resistors • 4 Band System – – – – 1st band is 1st digit 2nd band is 2nd digit 3rd band is a multiplier 4th band is tolerance Source: www.Digikey.com Week 4 Color 1st Band 2nd Band Multiplier Tolerance Black 0 0 1X100 1% Brown 1 1 1x101 2% Red 2 2 1x102 Orange 3 3 1x103 Yellow 4 4 1x104 Green 5 5 1x105 0.5% Blue 6 6 1x106 0.25% Violet 7 7 1x107 0.1% Gray 8 8 1x108 0.05% White 9 9 1x109 Gold n/a n/a 1x10-1 5% Silver n/a n/a 1x10-2 10% Week 4 Source: www.elexp.com Ohm’s Law (4.4) V = IR V is voltage across device I is current through device R is the resistance of the device Week 4 Ohm’s Law Examples (4.4) • V = IR • How much voltage is across a 100 Ohm resistor if 3A are flowing through it? • I = V/R • How much current is going through a 25 kiloohm resistor if it has 30V across it? • R = V/I • How much resistance is in a device that has 240V across it, and 10 A flowing through it? Week 4 Series and Parallel • Series: have the same current passing through each component – Resistors: Req = R1 + R2 + … + Rn – Capacitors: 1/Ceq = 1/C1 + 1/C2 + … + 1/Rn – Inductors: Leq = L1 + L2 + … + Ln • Parallel: have the same voltage across each component (connected by the same nodes) – Resistors: 1/Req = 1/R1 + 1/R2 + … + 1/Rn – Capacitors: Ceq = C1 + C2 + … + Cn – Inductors: 1/Leq = 1/L1 + 1/L2 + … + 1/Ln Week 4 Series and Parallel Week 4 Power Calculation (4.5) P = IV P is power I is current V is voltage Week 4 Power Calculation Examples (4.5) • How much power is being applied? • 13.8V across, 10A through • 12.5V across, 2.5A through • How much voltage? • 200W device, 40A through • How much current? • 50V across, 500W device Week 4 Decibels (4.5) • Power – Amplifier gain – Attenuation (gain < 1) – “Half power” is at 3.01dB • Voltage/Current Week 4 Decibel Calculation (3.6) • Increase power from 5W to 10W: • Gain = 10 log (10/5) • Gain = 3.01 dB • Decrease power from 12W to 3W: • Gain = 10 log (12/3) • Gain = 6.02 dB • Increase power from 20W to 200W: • Gain = 10 log (200/20) • Gain = 10 dB Week 4 Storing Energy (4.6) • Capacitance: storing energy in an electrical field – – – – Parallel plates Measured in Farads Acts as open circuit at low frequency Acts as short circuit at high frequency • Inductance: storing energy in a magnetic field – – – – Week 4 Coil of wire Measured in Henries Acts as short circuit at low frequency Acts as open circuit at high frequency Reactance • Reactance: also resists current flow in AC circuits, but is due to capacitance and inductance. – As frequency increases, reactance increases in an inductor – As frequency increases, reactance decreases in a capacitor – Measured in Ohms Week 4 Impedance • Impedance: resists current flow in AC circuit (similar to resistance in DC circuits) – Measured in Ohms • Impedance must be matched for maximum power transfer (will discuss during antenna lecture) Week 4