auxcom chapter 1

Auxiliary Communications Specialty Course

Flotilla Maui Specialty Course140-03-26


Chapter One

Basic Marine Radiotelephone

Systems. Nomenclature

and Theory


• Cycle = a single complete reversal of an alternating current (One wave)

• 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.

Terms of Art


Radio Waves


Frequency Conversions

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)


.2182 GHz

2.1820 MHz

2,182.000 kHz

2,182,000.000 Hz

Frequency Numbering


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

Frequency Spectrum


Ionosphere

Sky Waves Penetrating Ionosphere

Sky Waves Reflected

from Ionosphere

Sky Waves & the Ionosphere


Skip Distance

Ionosphere

Sky Wave Transmissions

Radio Skip


Ionosphere (Night)

Ionosphere (Day)

MF Wave

VHF Wave

Sky Wave (D

ay)

Sky Wave (Night)

Ground Wave

A

B C

D

Propagation CharacteristicsHF vs. VHF


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


Station

1

Station

1

Station

2

Station

2

Simplex

156.8 MHz

Send & Receive

(CH 16)

DuplexSend Receive

Receive Send

161.8 MHz

157.2 MHz

(CH 24)

Types of Circuits


Three Functions ofMarine Radiotelephone

•SAFETY

•OPERATIONS

•BUSINESS


2 – 30 MHz SSBRadio 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.


Power Distribution (Watts)

Lower Sideband

Frequencies (LSB)

Upper Sideband

Frequencies (USB)

Carrier Frequency

(No Intelligence)

1/6 2/3 1/6

Am

plit

ude

Frequency


Double SidebandSuppressed Carrier

Am

plit

ude LSB Frequency USB Frequency

Carrier

Frequency

Frequency

For Single Sideband, only LSB or USB is Transmitted


AM Transmissions Wave

FM Transmissions Wave

Examples of Waves


2 – 30 MHz Ground Wave & Sky Wave

Transmissions

(1,000s of Miles Possible)

156 – 158 MHz Line of Sight Transmissions

(25 Miles Typical)

HF vs VHF


Line of Sight

Mostly 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)

VHF-FM Marine Bands(156-162MHz)


• NO – Radio Watch Required

• NO – Protections from Interference

• NO – Foreign Vessels Can Not Use

• NO – Weather / Marine Info Available

• Limited to 5 Watts

Citizens Band (CB) Radio


Radio Repeater

INReceive

Freq. ARCVR

XMTR OUTTransmit

Freq. B


Antenna Types

2 – 30 MHz 156 – 158 MHz

Land stations Directional Directional

Vertical Vertical

Horizontal Wire

Shipboard Vertical Vertical

Directional


Antenna Radiation Patterns

Horizontal Plane PatternAntenna Axis

SOLID PATTERN

Vertical Plane Pattern

Antenna Axis

180

225

135

270 90

315 45

0


Antenna Axis

3 db 3 db6 db 6 db

9 db 9 db

ANTENNA RADIATION PATTERNS vs GAIN


Roll and pitch causes signal loss with narrow-beam high-gain antennas

High-Gain Antenna


Lower gain antennas are less affected by roll and pitch in normal coverage areas.

Lower-Gain Antenna


• USE A GOOD GROUND

• PROVIDE LIGHTNING PROTECTION

• USE CAUTION NEAR OVERHEAD POWER AND TELEPHONE LINES

• DISCONNECT ANTENNA DURING SEVERE THUNDER STORMS

Antenna SafetyCautions

auxcom chapter 1

Self Improvement

wave frequency

amplitude frequency

frequency spectrum

hz frequency numbering

lowergain antenna

antennas highgain antenna

voice f3e frequency

ssb radio system ground