Radio signals fundamentals
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Radio & Signals Fundamentals. 2.1 – Radio Signals & Waves. System of Metric Units. Tera T10 12 1,000,000,000,000 Giga G10 9 1,000,000,000 Mega M10 6 1,000,000 Kilo k 10 3 1,000 Basic Unit 10 0 1 Milli m10 -3 0.001 Micro μ 10 -6 0.000001

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Radio & Signals Fundamentals

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Radio signals fundamentals

Radio & Signals Fundamentals

2.1 – Radio Signals & Waves

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System of metric units

System of Metric Units

TeraT10121,000,000,000,000

GigaG1091,000,000,000

MegaM1061,000,000

Kilok1031,000

Basic Unit1001

Millim10-30.001

Microμ10-60.000001

Nanon10-90.000000001

Picop10-120.000000000001

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Radio signals fundamentals

Units of Measurements

109 106 103 102 101 100 10-1 10-2 10-3 10-6 10-9 10-12

G M k h da d c m µ n p

giga mega kilo hecto deca deci centi milli micro nano pico

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Pop quiz 2 1 metric system

Pop Quiz – 2.1 (Metric System)

  • Questions

    • T4E07-11

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T5b01 how many milliamperes is 1 5 amperes

T5B01How many milliamperes is 1.5 amperes?

A.15 milliamperes

B.150 milliamperes

C.1,500 milliamperes

D.15,000 milliamperes

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T5b02 what is another way to specify a radio signal frequency of 1 500 000 hertz

T5B02What is another way to specify a radio signal frequency of 1,500,000 Hertz?

A.1500 kHz

B.1500 MHz

C.15 GHz

D.150 kHz

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T5b04 how many volts are equal to one microvolt

T5B04How many volts are equal to one microvolt?

A.One-one millionth of a volt

B.One million volts

C.One thousand kilovolts

D.One-one thousandth of a volt

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Radio signals

Radio Signals

  • Radio equipment either generates or manipulates radio “signals”

  • Signals are electrical energy used to exchange information

    • Inside or outside of a radio

  • Other signals

    • Static (atmosphere, lightning)

    • Electrical noise (computers and motors)

    • Power lines (buzzing & humming)

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Frequency

Frequency

  • Frequency

    • AC current reverses or “oscillates” X number of times per second

      • Household current = 60 Cycles per second

      • RF current = Typically >20,000 CPS

    • Cycles per second referred to as Hertz, abbreviated Hz

      • 60 CPS = 60 Hz

      • 1,000 CPS = 1 KHz

      • 1,000,000 CPS = 1 MHz

    • Frequency is referred to as f

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Audio vs radio frequencies

Audio vs. Radio Frequencies

  • Audio frequencies are those that we can hear

    • <20,000 Hz or 20 kHz are in the audio range, therefore are referred to as audio frequencies (AF)

  • Frequencies above 20 kHz are radio frequencies (RF)

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Harmonics

Harmonics

  • Even or odd integer multiple of fundamental frequency

    • Second harmonic of 3.5 MHz = 3.5 MHz X 2 = 7 MHz

    • Third harmonic of 7 MHz = 7 MHz X 3 = 21 MHz

    • Fourth Harmonic of 50 MHz = 50 MHz X 4 = 200 MHz

  • Used in radio design to shift frequencies and create new signals

  • Can be bad actors

    • Spurious emissions can cause interference

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Harmonics1

Harmonics

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Phase

Phase

  • Phase describes relationship between two signals or components of a signal in time

  • Measured in degrees

    • 360 degrees in one complete cycle

  • Voltage & Current

    • When voltage & current are aligned in time = in phase

    • When voltage lags current or vice versa, circuit is out of phase

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Phase1

V+

0V

time

V-

One Cycle

Phase

90 Degrees

180 Degrees

0 Degrees

360 Degrees

270 Degrees

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The radio spectrum

The Radio Spectrum

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Radio signals fundamentals

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Wavelength

Wavelength

  • Distance that a wave travels in one complete cycle

  • Represented by the Greek letter λ (lambda)

  • Radio waves travel at the speed of light (300,000,000 mps) (c)

  • Wavelength (in meters) = c/f in hertz or 300,000,000/f(Hz)

  • Truncated, this means that λ = 300/f (in MHz)

  • In practice, 300 / 50 Mhz = 6 meters

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Wavelength1

Wavelength

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Wavelength formula

300

Freq (MHz)

Wavelength (λ) Formula

To convert from frequency to wavelength:

Wavelength (λ) =

(In Meters)

Wavelength and Frequency are Inversely Proportional. As one goes up, the other must go down.

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The relationship of frequency and wavelength

V+

0V

time

V-

One Wavelength (Distance)

One Cycle (Time)

The Relationship of Frequency and Wavelength

The distance a radio wave travels in one cycle is called wavelength.

distance

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Radio signals fundamentals1

Radio & Signals Fundamentals

2.2 - Modulation


Modulation demodulation

Modulation & Demodulation

  • A transmitter performs two major functions

    • Generates radio waves

    • Adds intelligence to the signal

    • Process of adding intelligence is modulation

  • A receiver performs two major functions

    • Receives radio waves

    • Extracts the intelligence from the RF signal

    • Process of extracting the intelligence is demodulation

  • An RF signal that carries no intelligence is unmodulated

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Basic modes

Basic Modes

  • Simplest RF signal is a continuous wave, abbreviated CW

    • One frequency, transmitter is on all the time, strength never changes

  • Combination of modulation method and information type is the communication mode

  • Simplest mode is a continuous wave turned on and off in some pattern, such as Morse code, or radiotelegraphy

  • Digital or data mode uses binary data to modulate the signal

  • Analog modes use information understood by humans such as voice

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Modulation methods

Modulation Methods

  • Modulation can occur in three ways by changing either the:

    • Amplitude of the signal

      • Amplitude Modulation (AM)

    • Frequency of the signal

      • Frequency Modulation (FM)

    • Phase of the signal

      • Phase Modulation (PM)

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Simple modulation

Simple Modulation

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Amplitude modulation

Amplitude Modulation

An unmodulated RF

carrier wave

A carrier wave AM

modulated with a

simple audio tone

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Am and ssb

AM and SSB

An unmodulated RF

carrier requires narrow

bandwidth

Modulation of the carrier

creates sidebands. This

requires more bandwidth.

Transmitter power is spread across this bandwidth

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Am and ssb1

AM and SSB

The carrier contains no

audio information.

The sidebands contain

duplicate audio information

By filtering out the carrier and one sideband, we save spectrum and concentrate our RF energy into a narrower bandwidth.

SSB is therefore more efficient.

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Am and ssb2

AM and SSB

When AM is not modulated (when you are not talking), the transmitter remains at full power

When SSB is not modulated the transmitter output power drops to almost nothing.

When either AM or SSB is over-modulated the signal may cause “splatter,” and interfere with other stations.

The process of extracting speech or music from an AM or SSB signal is called detection

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Frequency modulation

Frequency Modulation

  • Frequency varies in proportion to the modulating signal

  • Amount frequency varies when modulated is called deviation

  • FM transmitters operate at full power at all times, even when you are not talking.

  • When over-modulated, the signal can be so wide (bandwidth) it may interfere with adjacent channels. This is called over-deviation.

  • Speaking louder into the microphone may cause over-deviation

    • Eliminate by moving the microphone away from your mouth or speaking more softly

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Frequency modulation1

Frequency Modulation

  • FM signals have one carrier and several sidebands

  • 5-15 kHz wide

  • Amplitude doesn’t change, same power all the time

  • Limiter circuit strips away all amplitude variations, including noise

  • Compare AM radio to FM Radio

    • Static

    • Engine noise

    • Lightning

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Frequency modulation2

Frequency Modulation

  • A: Unmodulated carrier, full power at all times

  • B. Waveform of modulating signal

  • C. Modulated carrier with frequency deviation and constant amplitude

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Phase modulation

Phase Modulation

  • Very similar to frequency modulation

    • In FM, the frequency of the signal is varied

    • In phase modulation (PM), the phase of the signal is varied

  • Both modes received with the same circuitry

  • Most hams don’t know whether their “FM” transceiver is really FM or PM

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Am vs ssb

AM vs. SSB

  • AM

    • Sounds really nice

    • Inexpensive

    • Simpler equipment

    • Uses a lot of bandwidth

  • SSB

    • More efficient.

    • Further range based on same output power.

    • Narrower bandwidth, more room on crowded bands.

    • All modern HF radios support SSB

    • Most common voice mode on HF bands

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Ssb cw

SSB & CW

  • SSB uses less bandwidth than FM

    • Typically 2-3 kHz vs. 5-15 kHz

    • Power concentrated into narrow bandwidth

    • Allows comms over longer ranges and under poor conditions

    • Below 10 MHz use LSB (except 60 meters)

    • Above 10 MHz use USB

  • CW uses even less bandwidth

    • 150 Hz (Correct table 2-3)

    • Best mode for weak signal communications

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Ten minute break

Ten Minute Break

Be Back On Time!


Radio signal fundamentals

Radio & Signal Fundamentals

2.3 – Radio Equipment Basics

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Basic station organization

Basic Station Organization

Antenna

T-R Switch

Transmitter

Receiver

Power Supply

GROUND!

Something’s Missing!

  • Transmitter

  • Receiver

  • Antenna

  • T-R switch

  • Power Supply

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Basic station organization1

Basic Station Organization

Antenna

T-R Switch

Transmitter

Receiver

Power Supply

  • Transmitter (XMTR)

    • Generates a signal that carries speech, Morse code or data info

  • Receiver (RCVR)

    • Recovers the speech, Morse code or data info from a signal

  • Transceiver (XCVR)

    • Combines transmitter and receiver into one unit with self contained T-R switch

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Transcievers

Transcievers

Transmitter and receiver combined in one unit

Xmtr and rcvr share circuitry

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Antenna feed line

Antenna & Feed Line

  • Antenna

    • Turns energy from the transmitter into radio waves

    • Captures radio waves, turns them into signals for the receiver

  • Feed Line

    • Also called transmission lines

    • Connects the antenna to the transmitter and receiver

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Repeaters

Repeaters

Special kind of relay station

Receive and transmit at the same time

Weak signal is received, amplified and retransmitted

Receives and transmits on slightly different frequencies

Uses a duplexer instead of a T-R switch

Provides relay for weak and mobile stations, extends their coverage

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Repeaters1

Repeaters

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Accessory radio equipment

Accessory Radio Equipment

  • Power Supply

    • Converts household electrical power to power that can be used by the other station equipment

  • Microphone

    • Turns the operator’s voice into electrical signal called “audio”

  • Speaker

    • Turns audio signals into sound waves

  • Headphones

    • Used in place of speaker when listening to weak signals or in high ambient noise environments

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Accessories amplifiers

Accessories – Amplifiers

  • Amplifier

    • Increases the strength of a signal

    • Can be internal or external

  • Preamplifier

    • Increases the strength of a signal from the antenna before it is sent to the receiver

  • Power Amplifier (Linear)

    • Increases the strength of the a signal from the transmitter before it is sent to the antenna

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Power amplifiers

Power Amplifiers

Amplifiers increase the power output of the

transmitter

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Pop quiz section 2 3

Pop Quiz – Section 2.3

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T7a10 what device increases the low power output from a hand held transceiver

T7A10What device increases the low power output from a hand-held transceiver?

A.A voltage divider

B.An RF power amplifier

C.An impedance network

D.A voltage regulator

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Radio signals fundamentals

T4A10What is the source of a high-pitched whine that varies with engine speed in a mobile transceiver’s receive audio?

A.The ignition system

B.The alternator

C.The electric fuel pump

D.Anti-lock braking system controllers

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Radio signals fundamentals

T1F09What type of amateur station simultaneously retransmits the signal of another amateur station on a different channel or channels?

A.Beacon Station

B.Earth Station

C.Repeater Station

D.Message Forwarding Station

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See you next week

See you next week!


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