Radio Station Setup and Electrical Principles Covers sections: T4A-T5D Seth Price, N3MRA February 20, 2016
Outline 4.1 Station Setup 4.2 Operating Controls 4.3 Electronic Principles 4.4 Ohm s Law 4.5 Power Calculations 4.6 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*
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 www.ke4nyv.com
Typical VHF Radio (4.2)
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
Typical HF Radio (4.2)
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.
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
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
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
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).
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
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)
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?
Common Schematic Symbols (4.3) Name Symbol Units Resistor Potentiometer Voltage Supply Inductor Capacitor LED Ohms Ohms Volts Henries Farads n/a
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
Resistor Color Codes (4.3) Used to specify value and tolerance of resistors 4 Band System 1 st band is 1 st digit 2 nd band is 2 nd digit 3 rd band is a multiplier 4 th band is tolerance Source: www.digikey.com
Color 1 st Band 2 nd Band Multiplier Tolerance Black 0 0 1X10 0 1% Brown 1 1 1x10 1 2% Red 2 2 1x10 2 Orange 3 3 1x10 3 Yellow 4 4 1x10 4 Green 5 5 1x10 5 0.5% Blue 6 6 1x10 6 0.25% Violet 7 7 1x10 7 0.1% Gray 8 8 1x10 8 0.05% White 9 9 1x10 9 Gold n/a n/a 1x10-1 5% Silver n/a n/a 1x10-2 10% 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
Ohm s Law Examples (4.4) V = IR I = V/R R = V/I How much voltage is across a 100 Ohm resistor if 3A are flowing through it? How much current is going through a 25 kiloohm resistor if it has 30V across it? How much resistance is in a device that has 240V across it, and 10 A flowing through it?
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
Series and Parallel
Power Calculation (4.5) P = IV P is power I is current V is voltage
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
Decibels (4.5) Power Amplifier gain Attenuation (gain < 1) Half power is at 3.01dB Voltage/Current
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
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 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
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)