Download Shuswap Amateur Radio Club – Basic Qualification

Shuswap Amateur Radio Club – Basic Qualification
SESSION # 3
POWER SUPPLIES
TRANSMITTERS
RECEIVERS
Instructors: Phil Baker & Rick Ryan-Lewis
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Transformer
Rectifier
Filter
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Transformer
Power In = Power Out
Power Formula P = VI
V = Volts
I = Amps
Output Voltage is directly proportional to turn ratio
Output Current is inversely proportional to turn ratio
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Alternating Current (AC)
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Sine Wave
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Half-Wave Rectifier – 1 diode
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Full-Wave Rectifier – 2 diodes
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Full-Wave Bridge Rectifier – 4 diodes
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Filter Capacitor
Ripple
Filter Capacitor is used to
achieve a constant DC voltage
with minimum ripple
The magnitude of the ripple is inversely proportional to
the capacitance of the filter
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
Regulator
Regulator ensures a constant output voltage for varying current
loads and minor fluctuations of the input voltage
Shuswap Amateur Radio Club – Basic Qualification
POWER SUPPLIES
SAFETY
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Grounded Chassis
Interlock Mechanisms
Key Operated On/Off
Bleeder Resistors
As little as 1/10 of an Amp and 30 Volts can be fatal
In case of an Emergency
TURN OFF THE POWER FIRST !!
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
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Send information – message or baseband signal
Must be converted to Radio Frequency (RF) signal
• RF Generator/Oscillator: Produces the carrier
• Modulator: Converts baseband signal to RF signal
• RF Power Amplifier: Increases RF signal power
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Continuous Wave (CW)
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On-off keying (O.O.K.)
Morse Code is transmitted as an interrupted carrier
Key click filter - choke in series with Key and
a capacitor across the contacts suppresses RF clicks
Power
Supply
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Modulation
Combines
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Original information signal
RF sine wave – Pure Carrier
Types
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Amplitude Modulation (AM)
Frequency Modulation (FM)
BANDWITH
If useful information is conveyed, then spectrum must be occupied
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Amplitude Modulation (AM)
Baseband modulating signal
RF Generator carrier signal
RF Signal from Modulator
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Amplitude Modulation (AM)
USB
Envelop of carrier must not reach zero
OVERMODULATION
produces Splatter on adjacent frequencies
LSB
AM signal has 2 symmetrical sidebands
Upper sideband - USB
Lower sideband - LSB
AM signal bandwidth occupies twice the highest
frequency sent to the modulator
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Single Side Band (SSB)
•The carrier and one sideband are eliminated
• Requires less power and half the bandwidth
Fig. 1
Fig. 2
Fig. 3
Conventional
AM Signal
Carrier Removed
(DSBSC)
Unwanted Signal
Removed
By
Balanced Modulator
By
Sideband Filter
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Single Side Band (SSB)
Carrier fc suppressed
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Single Side Band (SSB)
{
}
fc + fa
fc - fa
DSBSC
Filter
fc + fa
Unwanted sideband
removed
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Single Side Band (SSB)
1
2
Balanced Modulator removes
the carrier – (DSBSC)
Sideband Filter removes
unwanted sideband
4
Mixer converts sideband signal
to final output frequency
3
Variable Frequency Oscillator
determines output frequency
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Frequency Modulation (FM)
Baseband modulating signal
RF Generator carrier signal
Modulated Carrier Signal
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Frequency Modulation (FM)
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Superior noise immunity
Ease of tuning
High audio quality
The maximum limit of the instantaneous frequency in
either direction is called the maximum deviation
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Frequency Modulation (FM)
Frequency multiplier increases both frequency and deviation
Over deviation causes out of channel emissions and signal distortion
Normal deviation for two-way radio +/- 5 kHz
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Frequency Modulation (FM)
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No message signal – Output is an unmodulated
carrier
Normal bandwidth 10 – 20 kHz
Not used below 29.5 MHz – exceeds bandwidth limits
(6 kHz)
Mic gain too high (talking too loud or too close)
causes nearby frequency interference
Reactance modulator connected to an RF Power Amp
produces a phase modulation emission
Shuswap Amateur Radio Club – Basic Qualification
TRANSMITTERS
Power Amplifiers
Class A
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Single sideband AM modulation
Good linearity
Class C
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FM modulation
Non-linear
High efficiency
Approx ½ of the power supplied to the amplifier stage is
released as heat
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Receiver Fundamentals
Quality Parameters
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Frequency stability The ability of a receiver to
stay tuned to an incoming signal for a long period.
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Sensitivity The ability to receive weak signals.
Selectivity The ability to reject signals on
adjacent frequencies. The narrower the band pass
filter, the "higher" the selectivity.
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Receiver Fundamentals
The Audio Stage
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Amplifies the signal from the detector and raises it to a
level suitable for driving headphones or a speaker.
A transformer is generally used to match speaker
impedance
The Automatic Gain Control (AGC) circuit in AM receivers,
maintains constant audio output for varying RF signal strengths
The Squelch circuit mutes audio output when there is no signal
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
“Block diagram" of a "superhetrodyne" receiver
three amplifiers are shown,
the RF amplifier, the IF amplifier, and the AF amplifier.
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The Radio Frequency Amplifier
Amplifies input signal to a usable level
Ahead of Mixer to reduce noise. May contain a preselector
Matches antenna’s impedance to that of the receiver
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The Intermediate Frequency Amplifier
Where most of the amplification in a receiver takes place
There may be two or more stages of IF amplification
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The Audio Frequency Amplifier
The audio signal is amplified in the audio amplifier and
passed on to a speaker or phones
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The superhet receiver – Part 1
The RF amplifier and mixer/oscillator receive signals from
the antenna and then convert them to the IF frequency.
It is in the RF amplifier and mixer/oscillator sections of the receiver where
the actual operator tuning takes place.
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Mixer/Oscillator
The purpose of the mixer/oscillator is to translate the
frequency of the incoming signal to the "intermediate
frequency".
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Mixer
RF Signal
In a mixer stage, the output contains the SUM and the
DIFFERENCE of the input signal frequencies.
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Band Pass Filter
The filter block prior to the IF amplifier shapes the
"passband" of the receiver.
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The superhet receiver – Part 2
From IF amplifier onwards, it is a "fixed frequency
receiver" pre-tuned and optimized for the reception of a
signal on the IF frequency.
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Beat Frequency Oscillator
(BFO)
The BFO replaces the suppressed carrier signal
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Product Detector
( Demodulator)
Converts the RF signal back to the original message signal
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
AM Radio receiver with an IF of 455 kHz
RF Signal
600kHz
f1
f2 + f1 = 1,655 kHz
Mixer
f2
f2 – f1 =
455 kHz
Band Pass
Filter
Oscillator
1,055 kHz
455 kHz
Oscillator must produce a frequency
455 kHz below or above 600 kHz
IF Amplifier
Another signal corresponding to 455 kHz plus the
Oscillator frequency 1,055kHz (1510 kHz) will also be
converted and demodulated - Image Frequency
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Double Superheterodyne
Typically has six stages
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A radio frequency (RF) amplifier
Two conversion stages
Two band pass filters
A demodulator
Frequency is converted twice
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
Double Superheterodyne
A high frequency IF is first chosen to
bring a satisfactory image response
A low-frequency IF to bring
high selectivity and gain.
Two IF stages reduces Image Frequency problems
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The F M Receiver
A receiver for FM signals follows the same general
principles as a receiver for CW and SSB reception
A "limiter" before the discriminator removes noise peaks
and amplitude-changes before detection of the FM signal
Shuswap Amateur Radio Club – Basic Qualification
RECEIVERS
The F M Receiver
Frequency Discriminator recovers original message
waveform from an FM signal
Capture Effect: When more than one signal is present,
only the loudest signal will be demodulated
Shuswap Amateur Radio Club – Basic Qualification
TRANSRECEIVERS
Contains both Transmitter and Receiver
When the unit goes into transmit mode, the receiver is
muted and disconnected from the antenna, but not from
the power source