NMEA Antenna Seminar
2010 NMEA International Conference and Expo
Seattle, WA
David Morschhauser, Presenter/Moderator
Dr. John Jones, Digital Antenna
Don Henry, Shakespeare Antenna
Antenna Basics
• Any Conducting Material Will Work as an
Antenna on Any Frequency
• Only Reason for Specific Antennas Is to
Control Radiation Pattern
– Total Radiated Power Is Same
• Focused Radiation Pattern Results in Antenna
“Gain”
Antenna Aperture
Antenna
Voltage
Current
Aperture
Satellite Dish Aperture Is
Approximately the Dish Area
Radiation Pattern
90
75
60
45
30
15
0
Antenna Gain
• Measures the Ability to Focus Existing RF
Energy
• Measure Is in dB, a Ratio of
– Maximum Radiated Power to the Radiated Power
of an Isotropic Source (dBi)
– Maximum Radiated Power to the Radiated Power
of a ½ Wavelength Dipole (dBd)
Gain = 10 x log(Antenna Power/Reference Power)
Aperture Disturbances
• Aperture Size Is a Function of Wavelength
– VHF @ 162 MHz, Dipole Aperture ≈ 1.6 Feet
– SSB @ 30 MHz or Less, Dipole Aperture ≈ 8+ Feet
– Applications at 1+ GHz, Dipole Aperture << 1 Foot
• Antennas with Dipole Apertures
– VHF, SSB, Cell Phone, DGPS
• Conductors within Aperture Change Antenna
Characteristics
Example: Yagi-Uda
• Typical Antenna Design Takes Advantage of
the Effects Obtained Using Parasitic Elements
– Reflector Is 10% Longer Than Driven Element
– Directors Are 10% Shorter Than Driven Element
Driven
Directors
Reflector
90
75
60
45
30
0
15
Antenna Types
Application
Description
T or R
Type
VHF
Communication
T/R
GPS
Navigation
R
Microstrip
Loran
Navigation
R
Dipole
Satellite Comm
Communication
T/R
Parabolic
Satellite TV
Entertainment
R
Parabolic
Cellular
Communication
T/R
Dipole
SSB
Communication
T/R
Dipole
Dipole
Antenna Types
Application
Description
T or R
R
Type
DGPS
Navigation
Dipole
Radar
T/R
AM/FM
Collision
Avoidance
Entertainment
R
Dipole
AIS
Vessel Tracking
R
Dipole
Navtex
Information
R
Dipole
ADF
Direction Finding
R
Stacked Dipole
Mini-M
Communication
T/R
Reflector
Microstrip
Antenna Locations
Antenna Locations
• Objectives:
–
–
–
–
Preserve Antenna Aperture
Avoid Co- and Cross-channel Interference
Avoid Shadowing Potential Services
Avoid Damage from High-power Transmitters
Antenna Spacing
VHF
GPS
D-GPS
SSB
VHF
4
GPS
3
1/2
D-GPS
1
1
1/2
SSB
3
4
4
10
RADAR
2
(a)
2
2
SATCOM
6
6 (b)
10
6
(a) GPS, Satellite & Cell Antennas outside Radar Beam
(b) GPS Antennas below SATCOM Antenna Beam
Antenna Spacing
VHF
GPS
D-GPS
SSB
LORAN
1
2
2
3
Cell Ph
2
5 (c)
1
2
Sat TV
3
3
1
4
ADF
6
1
1
6
(c) Cell Transmissions Can Interfere with GPS Reception
Antenna Spacing
RADAR
RADAR
SATCOM
LORAN
Cell Ph
(d)
SATCOM
6
6
LORAN
3
6
1/2
Cell Ph
(a)
6
2
3
Sat TV
4 (e)
6
4
4
4
10
4
4
ADF
(d) Install Radar Antennas at Different Heights (18”)
(e) Sat TV Spacing Dependent on Radar Output Power
Antenna Spacing
Sat TV
Sat TV
4
ADF
4
ADF
4
Antenna Testing
• Electrical Testing Performed as Part of
Appropriate System Testing
– Connection Problems Identified
– Performance Problems Almost Always Due to
Connections & Transmission Line
• Physical Mounting & Structure
– Deflection Test
– Mounting Secure – No Spider-lines after Deflection
VHF Prerequisites
• Programmed with MMSI
• Connected to and Receiving Data from a GPS
if Available
• Appropriate Power Source Available
– Emergency Battery if Available
VHF Transceivers
• Line-of-sight Transmissions
• Equipment Self-contained
– Options Include Remote Mics, Remote Displays
• Controls Located at Watchstander Location
• Antenna Selection Based on Vessel and
Intended Use
• Coax Cable Connections ≤ 3dB Loss at 162
MHz
High Gain Pattern
Low Gain Pattern
VHF Testing
• RF & Power Test
• Voice Radio Check
– Convenient Channel – NOT 16 or 22A
• DSC Radio Check
Testing Described Is Installation Testing
VHF Transceiver Testing & Repair Requires FCC License
RF & Power Test Setup
+
-
A
V
Mic
Transmitter
Bird
Wattmeter
Antenna
Half Wave Connection
• Used for Testing When Test Meter Cannot be
Connected Directly to the VHF RF Output
• VHF Half Wave Cable Using RG-213
– Frequency = 156.75 MHz
Half Wave Cable Length = 299.8 * Vf / Freq * 2
Length Is in Meters
Vf Is the Cable Velocity Factor
Frequency Is in MHz
Test Parameters
Test Measurement
Nominal Value
Tolerance
1
RF Forward Power
25 Watts
≥ 20 Watts
2
RF Reflected Power
at DUT Output
Voltage at DUT
Input
Current at DUT
Input
0 Watt
≤ 3 Watts
12 Volts
≥ 11.7 Volts
3
4
Rated Transmit ≤ 125% Rated
Current
Transmit
Digital Selective Calling
(DSC)
• Required on All VHF and SSB Transceivers
Type Accepted in U.S. Since 1999
• Automates Hailing Process
– Hailing Channels 16 (VHF) and 2182 KHz (MF)
– Especially Important for Distress Calls
• Dedicated Channels for DSC Transmissions
– VHF Channel 70
– MF Channel 2187.5 KHz
– HF Channels 4207.5, 6312.0, 8414.5, 12577.0,
and 16804.5 KHz
Maritime Mobile Service
Identity (MMSI)
• Vessel’s “Phone Number”
• Four MMSI Types
–
–
–
–
Ship Station Identities
Group Ship Station Identities
Coast Station Identities
Group Coast Station Identities
• U.S. Coast Guard Station Identities
– Group Ship = 036699999
– Group Coast = 003669999
SSB Installation
Prerequisites
• VHF Transceiver Already Installed
• Programmed with MMSI
• Connected to and Receiving Data from a GPS
if Available
• Appropriate Power Source Available
Basic SSB Components
Vessel DC
Power
Optional: Control
Cable Connection
Antenna Lead-in
Mic
RF Coax
Transceiver
Coupler
Ground Straps
Ground Plane
Coax Cable Connections ≤ 2dB Loss at 2 - 30 MHz
Equipment Locations
• Transceiver Should Be Located in Accordance
with Vessel Owner’s Requirements
– Control Access from Watchstander’s Position for
Emergencies
• Antenna Location Depends on Type and
Vessel
• Antenna Coupler Location Determined by
Antenna
• Ground Plane and Construction Determined
by Antenna Coupler
Antenna Requirements
• Antenna Starts at Antenna Coupler
– Signals from Lead-in Wire Should Not Be Blocked
or Shunted to Ground
• Ideally, Antenna Is ¼ Wave Length
– At 2 MHz Antenna Would Be 120 Feet
– At 22 MHz Antenna Would Be 11 Feet
• At ¼ Wave Length, RF Signal Resonates on
Antenna, Resulting in Maximum Radiation for
a Given Power Level
Resonating Antenna
Antenna Coupler
Counterpoise
Ground Considerations
Join Grounds at the
Ground
SSB Antenna Alternatives
• 16 to 24 Foot Whip Antenna
• Various Rigging Configurations
–
–
–
–
–
Backstay
Split-backstay
Ketch
Center-fed Dipole
Whip
Antenna Construction
•
•
•
•
Lead-in Wire Is Part of Antenna
Insulated from Other Metallic Objects
Exposed Antennas ≥ 7’ above Deck Surface
Use Insulators to Connect to Rigging
Lead-in Standoffs
Ketch
3'
3'
Insulators
GTO-15 mounted
to standoffs
To Antenna Coupler
Backstay Installation
3'
GTO-15 mounted
to standoffs
Insulators
7'
Deck
Split Backstay
Insulators
GTO-15 mounted
to standoffs
7'
Deck
Ground System
• At Best – A Compromise
• Major Considerations
– Metal or Non-conductive Hull
– Salt or Fresh Water
• Conductor Selection
• Connection to Water
• Additional Ground Planes
Ground Requirements
Metal Hull
• Connect the Transceiver and Antenna Coupler
Directly to the Hull
• Ground Connections Use 2” Copper Strap
• Aluminum Hulls Use a Capacitive Coupling
• A Sealant or Anti-corrosive Gel May be
Employed to Create Coupling for Other
Dissimilar Metal Connections
• Antenna Coupler outside the Metal Enclosure,
if Possible
Ground Requirements
Non-metallic Hull
• Ground Plate or Ground Plane
– Plate > 2 Sq Ft; Including Area of Props, Shafts, if
Bonded to SSB Ground
– Plane > 100 Sq Ft; either Installed in Hull, or
Created Later Using 2” Copper Strap
• Connections to Engine Block and through
Hulls
• Ground Plane No More than 10’ below
Antenna Coupler
Cabin-top Ground-plane
SSB Testing
• RF & Power Test
• Voice Radio Check
– Convenient Channel – NOT 2182 KHz
– Also Avoid 3023 KHz and 5680 KHz
• DSC Radio Check
• Antenna Power and Balance
Testing Described Is Installation Testing
SSB Transceiver Testing & Repair Requires FCC GROL or
Higher Class License
RF Power Test
+
-
A
V
150 Watt
Mic
Transmitter
Bird
Wattmeter
Transmission
Line
Load
Test Parameters
Test Measurement
Nominal Value
Tolerance
1
RF Forward Power
150 Watts
≥ 120 Watts
2
RF Reflected Power
at DUT Output
Voltage at DUT
Input
Current at DUT
Input
0 Watt
≤ 5 Watts
12 Volts
≥ 11.7 Volts
3
4
Rated Transmit ≤ 125% Rated
Current
Transmit
Satellite Communications
• Wide Variety of Marine Communication Needs
• Receive Only
– GPS, Weather, TV, Other Entertainment
• Transmit/Receive
–
–
–
–
Voice
Video
Data/Fax
Internet
• Motion Compensated Systems
Typical Satellite System
Radome
Control Unit
Vessel Motion
Sensor
Power Supply
Satellite Constellations
Constellation Geometry
• Geostationary – Always in Same Relative
Position in Sky
• Non-stationary – Cross from Horizon to
Horizon while in Use
• Low Earth Orbit (LEO)
• Medium Earth Orbit (MEO)
• Some Systems Maintain a Minimum of Two
Satellites in View at All Times
Radome Location
•
•
•
•
Physically Secure Location
Clear View of as Much Sky as Practical
Follow Antenna Spacing Requirements
Outside Any Radar Array within 6 Feet
Line-of-Sight
-15° to
+85°
Blocked
From View!
Mast or Cabin
Structure
Radar Clearance
±15°
Below-Deck Equipment
• Control Unit – Not Normally Used for Vessel
Navigation; Install in Convenient Location
• Vessel Motion Sensor – Position as Close as
Practical to the Vessel Pitch-and-Roll Center
• Be Aware of Potential Magnetic Interference
When Fluxgate Compass Included with
Package
System Grounding
• 2” Grounding Strap
When Practical
• Connect Radome
and Control Unit
• Run Strap to Main RF
Ground Bus
Radome
Grounding
Strap
Control Unit
To RF
Ground
Connections
• Coax Cables in Accordance with Manufacturer
Recommended Signal Loss
• Multi-conductor Cables – Use Manufacturer
Provided Cables
• Splice Cables Using Ring Lugs and Suitably
Sized Terminal Strips
• Protect All Connections from Weather
Setup & Testing
• Set Up Service Identifiers
• Testing in Accordance with Manufacturer
Requirements
Measurement
Supply Voltage
(System Power Off)
Supply Voltage
(Maximum System Power)
Value
Minimum Voltage Specified
by the Manufacturer
Minimum Voltage Specified
by the Manufacturer
Antenna Power & Balance
+
-
A
V
Mic
Transmitter
Bird
Wattmeter
Transmission
Line
Antenna
Coupler
RF
Transmission
Measurements
Band
Frequency
Selected
RF Forward
Power
RF Reflected
Power
2000 KHz
4000 KHz
6000 KHz
8000 KHz
12000 KHz
16000 KHz
18000 KHz
22000 KHz
25000 KHz
Forward Power ≥ 120 Watts
Reflected Power ≤ 5 Watts
RF Current