Transcript Radio Station Setup and Electrical Principles

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