Technician License Course
Chapter 2
Radio and Signals Fundamentals
Handling Large and Small Numbers
Electronics and Radio use a large range of sizes –
billionths to billions. Powers of 10 – called Scientific
Notation – lets us use small numbers for calculating by
using prefixes like
• Kilo, Mega, Giga, Terra for large sizes.
– Examples: KiloHertz, MegOhms, GigaByte
• pico, nano, micro, milli for small sizes.
– Examples: picofarad, microhenry, millimeter
Abbreviations like: pF (picoFarad), mH (milliHenry), KHz
(KiloHertz), MHz (MegaHertz), GB (GigaByte)
Some Metric System Prefixes
Prefix
Abbreviation
Factor
Power of 10
Pico
p
0.000000000001
10 E-12
Nano
n
0.000000001
10 E-9
Micro
u
0.000001
10 E-6
Milli
m
0.001
10 E-3
Kilo
K
1000
10 E3
Mega
M
1,000,000
10 E6
Giga
G
1,000,000,000
10 E9
Terra
T
1,000,000,000,000
10 E12
Note: Use lower case prefix letters for less than 1
Move the decimal point to convert
To
From
Pico
p
Pico
p
Micro
u
Milli
m
Unit
Kilo
K
Mega
M
Giga
G
6
 9
 12
 15
 18
 21
3
6
9
 12
 15
3
6
9
 12
3
6
9
3
6
Micro
u
6
Milli
m
9

Unit
12
6
3
Kilo
K
15
9
6
3
Mega
M
18
12
9
6
3
Giga
G
21
18
12
9
6
3
3
Electromagnetic Waves
Radio is the use of ElectroMagnetic waves to carry
the information you want to send.
• The Radio Frequency voltage on an Antenna
creates an alternating Electric Field.
• The Radio Frequency current in an Antenna
creates an alternating Magnetic Field.
• At some small distance from the antenna, the
Electric and Magnetic fields combine into an
ElectroMagnetic Wave which spreads through
space.
Fundamentals of EM (Radio) Waves
Electric and Magnetic fields travelling at right
angles to each other make up a Radio Wave.
• Energy in the wave travels at the velocity of light,
300,000,000 meters per second (186,000 miles
per second).
• Energy spreads in all directions.
• Energy propagates in straight lines.
• Energy is absorbed by poor conductors.
• Energy is reflected by good conductors.
Wave Vocabulary
Before we study radio
waves, we need to learn
some wave vocabulary.
– Waveform (sinewave)
– Amplitude (Volts)
– Frequency (Hertz)
– Period (Seconds)
– Harmonics (1st, 2nd,
3rd, 4th, etc.)
– Wavelength (Meters)
Wavelength
Wavelength is the distance the energy travels
during one cycle of the magnetic or electric fields.
Wavelength (Meters) is Velocity of light divided by
Frequency (Hertz)
– 300,000,000 / Frequency in Hz.
– 300 / Frequency in MegaHertz.
– Higher Frequency  Shorter Wavelength.
– Lower Frequency  Longer Wavelength.
Wavelength
Radio Frequency (RF) Spectrum
A Spectrum is a range of sizes or features.
• The light spectrum in a rainbow consists of
colors. (Colors are radio frequencies with
wavelengths that human eyes can detect.)
• The Radio spectrum (RF) is the range of
electromagnetic wavelengths which will travel
through space. (Practically all wavelengths)
• The RF spectrum is divided into segments of
frequencies that have similar behaviors.
Radio Frequency (RF) Spectrum
VLF – Very Low Frequency, LF – Low Frequency, MF –
Medium Frequency, HF – High Frequency, VHF – Very
High Frequency, UHF – Ultra High Frequency, SHF –
Super High Frequency, EHF – Extremely High
Frequency
What are the Amateur Radio Bands?
Amateurs are allowed to transmit inside bands of
frequencies. There are too many bands to list on
one slide. Use the ARRL chart to study.
• Bands are allocated in MF, HF, VHF, UHF, and
SHF spectrum, (1.8 MHz and higher).
• Bands are named by frequency or wavelength.
• Bands are divided into segments for different
modes. On HF, voice at high end, digital lower
than voice, and CW exclusively at low end.
Bands and Frequencies
There are three ways to tell someone where
to meet you on the radio dial (spectrum).
– Frequency – a distinct frequency point.
Specified in KiloHertz (KHz), MegaHertz
(MHz), or GigaHertz (GHz)
– Wavelength – The wavelength in Meters or
centimeters. (300 / FMHz)
– Band – a group of adjacent frequencies
between a low end and high end.
Frequency vs. Band Examples
Amateurs are allocated bands of frequencies.
Bands are often named for the wavelength of a
frequency in the band.
Wavelength in Meters. L = (300 / FMHz)
– 300/146 MHz = 2.05 Meters
– 144MHz – 148MHz  2 Meters
Frequency in MHz. FMHz = (300 /L)
– 300 / 6 Meters = 50 MHz
– 6 Meters  50MHz – 54MHz
Station Effects of Wavelength
For the station antenna to efficiently send the radio
wave out into space, the antenna must be
designed for the specific operating frequency.
– Antennas with wavelengths greater than one
fourth of a wavelength can be very efficient.
– The antenna length compared to wavelength
will determine the strength at different angles
and directions.
– If the antenna is too short or too long, it might
cause the transmitter to reduce power.
Propagation Effects of Wavelength
Radio signals propagate through space and in the
atmosphere. Expected propagation distances
depend on the signal wavelength.
– Long and Medium wavelengths are best for
waves along the ground or water. (LF, MF)
– Short wavelengths are best for reflection by
the Ionospheric layers. (HF)
– Very Short wavelengths are only reliable for
line-of-sight propagation. (VHF, UHF, EHF)
Frequency versus Uses
Frequency
3000 MHz
Wavelength
0.10 Meters
UHF
300 MHz
VHF
30 MHz
1 Meter
10 Meters
HF
3 MHz
Radar
Cellphones
Aircraft
Line of Sight
Mobile Services
Shortwave
Sky Wave
100 Meters
Broadcasting
MF
300 KHz
LF
30 KHz
1000 Meters
Beacons
10,000 Meters Submarines
Ground Wave
Adding Information - Modulation
We use modulation to imprint information on the
radio signal.
Different modulation methods are called modes.
– Turn the wave on and off – CW
– Vary the amplitude – AM
– Vary the frequency – FM
– Vary both frequency and amplitude – Data
Modulation adds frequencies to the signal which
result in a transmitted bandwidth.
Signal Bandwidths
Keeping your signal in the Band
Amateur stations may use any frequency in
their authorized bands but all frequencies of
the signal must be inside the band limits.
– Never operate with the transmitter dial set at
the band limit.
• Inaccurate Dial Calibration
• Frequency drift
– Set the transmitter dial far enough away from
the limit to keep modulation frequencies
inside the band.
Morse Code – On and Off
Efficient method of
modulation and high
Transmitter utilization.
• Large Signal to Noise
Ratio, due to narrow
bandwidth, ~150Hz.
• Slow information rate
when sent by humans.
Amplitude Modulation (AM)
In AM, the information
amplitude (voice) varies
the RF Signal amplitude.
• Low efficiency.
• Bandwidth depends on
information.
Characteristics of Voice AM
AM signals consist of
three components:
– Carrier
– Lower sideband
– Upper sideband
AM bandwidth is twice
the voice bandwidth.
Single Sideband Modulation (SSB)
We can improve
efficiency of AM
transmission by
transmitting only one
sideband and no carrier.
• Either sideband has all
the voice information.
• A carrier is generated
at the receiver for
reception.
Amateur SSB Use
SSB is the primary voice mode for HF.
– Principle advantage is narrower bandwidth
than FM voice and more efficient than AM
– Use Upper Sideband above 10MHz and
Lower Sideband below. A tradition.
SSB is used on VHF for long-distance weak
signal contacts.
– VHF radios for SSB are called All-Mode.
– Operation is on a sub-band to avoid FM.
Frequency Modulation (FM)
For FM, the voice signal
amplitude causes the frequency
of the RF Signal to deviate.
• FM signals are more resistant
to the effects of noise but
require more bandwidth.
• FM bandwidth (for voice) is
between 5 and 15 kHz.
• Voice amplitude influences FM
bandwidth.
Amateur FM Use
FM is the primary voice mode above
29MHz. FM is not allowed on Amateur
bands below 29MHz.
– Principal advantage over SSB on VHF is
immunity to noise and frequency drift.
– Repeaters and Packet stations use FM.
– Bandwidth of 5 to 15 KHz is normal.
Common Digital Modes
RTTY (Radioteletype).
– Uses Baudot code and FSK with 170 Hz shift
between the two tone frequencies.
TORs (Teletype over radio) – some error correction:
– PACTOR
– AMTOR
PACKET – error correction and reliable transport.
PSK31 – error correction by backspacing , low power,
minimum bandwidth.