AUXCOM Chapter One

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http//www.cgaux.org/
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Chapter One

• Basic Marine Radiotelephone Systems. Nomenclature
  and Theory

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• Cycle a single complete reversal of an
  alternating current
• Frequency the number of cycles per second
• Hertz (Hz) one Hz equals one cycle per second

These units of frequency measurement honor
Henrich Hertz, an early pioneer in radio.
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FREQUENCY CONVERSION
1 Hz 1 Cycle per Second 1,000 Hz 1
kHz (Kilo Hertz) 1,000 kHz 1 MHz (Mega
Hertz) 1,000 MHz 1 GHz (Giga Hertz)
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FREQUENCY .2182 GHz 2.182
MHz 2,182. kHz 2,182,000. Hz
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FREQUENCY SPECTRUM 3-30 kHz Very Low Freq.
VLF 30-300 kHz Low Freq.
LF 300-3,000 kHz Medium Freq. MF 3-30
MHz High Frequency HF 30-300 MHz
Very High Freq. VHF 300-3,000 MHz Ultra
High Freq. UHF 3-30 GHz Super High Freq.
SHF
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Sky Waves Penetrating Ionosphere
Ionosphere
Sky Waves Reflected from Ionosphere
Sky Waves the Ionosphere
Fig 1-2
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Ionosphere
Skip Distance
Sky Wave Transmissions
Fig 1-3
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Ionosphere (Night)
Ionosphere (Day)
MF Wave
VHF Wave
Sky Wave (Night)
Sky Wave (Day)
Ground Wave
B
C
Propagation Characteristics HF vs. VHF
A
D
Fig 1-4
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Emission Designations First 3 Characters
Bandwidth Last 3 Characters Emission
Type Example 2K8J3E 16KF3E Bandwidth
Emission Type Bandwidth Emission Type J3E
Single Sideband, Suppressed Carrier, Voice F3E
Frequency Modulated, Voice
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Types of Circuits
156.8 MHz
Send Receive
(CH 16)
Station 1
Station 2
Simplex
Duplex
Send Receive
161.8 MHz
Station 1
Station 2
Receive Send
157.2 MHz
(CH 24)
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Three functions of Marine Radiotelephone
SAFETY
OPERATIONAL
BUSINESS
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2 30 MHz SSB Radio System Ground Wave vs. Sky
Wave More Power More Range FCC Limit of 150
Watts AM vs. SSB 2182 kHz International
Distress Calling 2670 kHz Coast Guard
Public Freq.
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Power Distribution (Watts)
1/6 2/3 1/6
Carrier Frequency (No Intelligence)
Lower Sideband Frequencies (LSB)
Upper Sideband Frequencies (USB)
Amplitude
Frequency
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Double Sideband Suppressed Carrier
LSB Frequency
USB Frequency
Amplitude
Carrier Frequency
Frequency
For Single Sideband, only LSB or USB is
Transmitted
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AM Transmissions Wave
FM Transmissions Wave
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2-30 MHz vs 156-158 MHz
2 30 MHz Ground Wave Sky Wave Transmissio
ns (1,000s of Miles Possible) 156 158
MHz Line of Sight Transmissions (25 Miles
Typical)
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156 - 162 MHz VHF-FM System
Line of Sight Free of Static For Vessels 25
Watts Max (with 1 Watt Switch)

• Channel 16 156.8 MHz (National Distress, Safety
  and Calling)
• Channel 6 Internship Safety
• Channel 13 Navigational (Bridge to Bridge)
• Channel 70 Digital Selective Calling (DSC)

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Citizens Band Radio (CB)

• NO Radio Watch Required
• NO Protections from Interference
• NO Foreign Vessels Can Not Use
• NO Weather / Marine Info Available
• Limited to 5 Watts

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Radio Repeater
Receive Freq. A
IN
RCVR
Transmit Freq. B
OUT
XMTR
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Antenna Types
2 30 MHz 156 158 MHz Land stations
Directional Directional Vertical Vertical
Horizontal Wire Shipboard Vertical Vertical
Directional
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ANTENNA RADIATION PATTERNS
Vertical Plane Pattern
180
Antenna Axis
225
135
Horizontal Plane Pattern
Antenna Axis
270
90
315
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SOLID PATTERN
0
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ANTENNA AXIS
3 db
3 db
6 db
6 db
9 db
9 db
ANTENNA RADIATION PATTERNS vs GAIN
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Roll and pitch cause signal loss with narrow-beam
high-gain antennas
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Lower gain antennas are unaffected by roll and
pitch in normal coverage areas.
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• ANTENNA SAFETY PRECAUTIONS
• USE A GOOD GROUND
• PROVIDE LIGHTNING PROTECTION
• USE CAUTION NEAR OVERHEAD POWER AND TELEPHONE
  LINES
• DISCONNECT ANTENNA DURING SEVERE THUNDER STORMS