Marine Antenna Installations - NMEA antenna installations ibex... · Antenna Basics VHF, SSB,...

IBEX 2011

Speakers:

David Gratton- Martek-Palm Beach, FLJohnny Lindstrom- Westport Shipyard, WA

Marine Antenna Installations

Property of the NMEA. Shall not be copied or re-distributed.

Seminar Overview

• Antennas– AIS, Cellular, Radar, Satellite, SSB, VHF, WX

• Location – Aesthetic vs. Practical vs. Customer Requests

• Testing• Installations

Antenna BasicsVHF, SSB, AM/FM, AIS, Cellular

• Any Conducting Material Will Work as an Antenna on Any Frequency

• Only Reason for Specific Antennas Is to Control Radiation Pattern (n/a for SSB on most vessels)

– Total Radiated Power Is Same

• Focused Radiation Pattern Results in Antenna “Gain” (n/a for SSB on most vessels)

• Example: Spot light vs. Flood light (n/a for SSB)


Antenna LocationsVHF, SSB, AM/FM, AIS, Cellular

• Objectives:• Preserve Antenna Aperture• Avoid Co- and Cross-channel Interference• Avoid Shadowing Potential Services• Avoid Damage from High-power Transmitters• It is not possible to locate all antennas in

optimum locations. Most all installations are a compromise.


• GPS, Satellite & Cell Antennas must be outside Radar Beam

• GPS Antennas below SATCOM Antenna Beam

• Cell Transmissions Can Interfere with GPS Reception

• Multiple Radar Antennas at Different Heights (18”)

• Sat TV Spacing Dependent on Radar Output Power

Antenna SpacingImportant Notes


Antenna Spacing (Feet)

VHF GPS SSB Radar Cell Sat TVVHF 4 3 3 2 2 3

GPS 3 1/2 4 (a) 5 (c) 3

SSB 3 4 10 4 2 4

Radar 2 (a) 2 2 1 4

Cell 2 5 (c) 2 1 1 4

Sat TV 3 3 4 4 4 6


Antenna Types

Application Description T or R Type

VHF Communication T/R Dipole

Sideband (SSB) Communication T/R MarconiAM/FM Entertainment R DipoleAIS Vessel Tracking R DipoleCellular Communication T/R DipoleGPS Navigation R Micro stripSatellite Comm. Communication T/R ParabolicSatellite TV Entertainment R Parabolic

Radar Collision Avoidance T/R ReflectorWeather Environment R Micro strip

Antenna Locations

Radiation Pattern ExampleVHF, AM/FM, AIS, Cellular

90

30

45

6075

15

0

3D ViewTop Down View Property of the NMEA. Shall not

be copied or re-distributed.

High & Low Gain Patterns

Low Gain

High Gain

Antenna GainVHF, AM/FM, AIS, Cellular

• Measures the Ability to Focus Existing RF Energy (spot light vs. flood light)

• 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)


Aperture DisturbancesVHF, SSB, AM/FM, AIS, Cellular

• Aperture Size Is a Function of Wavelength– VHF @ 156.800 MHz, Dipole Aperture ≈ 1.6 Feet– Applications at 1+ GHz, Dipole Aperture << 1 Foot

• Antennas with Dipole Apertures– VHF, AIS,Cell Phone, AM/FM, DGPS

• Conductors within Aperture Change Antenna Characteristics


Antennas- VHF & SSB

• Physical Support– Withstand 10 Lbs. Force 24” from the Mounting– How do we measure?– Two-point Mount for Antennas Longer Than 8’

• Arrangement– Maximize Spacing to Minimize Interference

• Safety– SSB Shock Hazard due to high voltage– Radar Radiation Hazard


VHF Test Parameters

Test Measurement Nominal Value Tolerance

1 RF Forward Power 25 Watts ≥ 20 Watts

2 RF Reflected Power at DUT Output

0 Watt ≤ 3 Watts

3 Voltage at DUT Input

13.6 Volts ≥ 12 Volts

DUT= Device Under Test


Antenna Requirements-SSB

• Antenna Starts at Antenna Coupler Ground– 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– Obviously not practical

• At ¼ Wave Length, RF Signal Resonates on Antenna, Resulting in Maximum Radiation for a Given Power Level

SSB Installation

• Ground System Complexity– Hull Material: Metal Hulls Are an Excellent Antenna

Counterpoise– Salt Water Is More Conductive Than Fresh Water– Much more “effective area” is required in fresh water

• Ground Conductors– Surface Area Is Important– RF travels on surface, not conductor– Copper Straps and Copper Tubes (hydraulic tubing)

Have Greater Surface Area for a Given WeightProperty of the NMEA. Shall not

be copied or re-distributed.

SSB Test Parameters

Test Measurement Nominal Value Tolerance

1 RF Forward Power 150 Peak Watts ≥ 120 Peak Watts

2 RF Reflected Power at DUT Output

1 Watt ≤ 5 Watts

3

3 Voltage at DUT Input

13.6 Volts ≥ 12 Volts

Signal strength meter required to measure antenna output

Radar Location

• Beam Is Above Crew Spaces• No Obstructions on Critical Azimuth Bearings• Power density?

Radar Transmits a Focused Energy Beam That Can Be a Hazard to Humans and Other Receiving Equipment

Radar Mounting

• Consider Weight of Unit vs. Strength of Location– Many Fiberglass Arches Won’t Support Open Array

Radar Units without Reinforcement• Optimum Attitude Level with Horizon When

Cruising– Powerboats: 2° Down at Rest or Horizontal ± 2°

at Cruise– Sailboats: Horizontal ± 2°

• Vertical Height Within 30’ of Water Level to Avoid Missing Close in Targets (discuss)


Radar Connections

• Cable between Display and Array Unit Performs Multiple Functions– Longer Lengths Are Available from Manufacturer– Best practice is to use Manufacturer Approved

Extension Cables when required, instead of splicing

• Use Shielded Power and Communications Cables• Ground Units to RF ground bus to Reduce EMI


Wind & Weather Sensors

• Must be installed in 360° “Clean Air”– This assures wind & temperature readings will be accurate.– Check alignment placement (differs with manufacturers).

• Mast installations:– Mount at top (power or sail).

• Hardtop installations:– Mount at least 1 ft. above, and 3’ back from front of hardtop.

• Radar Arch installations:– Mount at least 1 ft. above arch.


Wind & Weather Sensors:Dead Air Zone

Satellite Constellation Geometry• Geostationary – Always in Same

Relative Position in Sky.TV, Communications, Weather22,000 miles

• Non-stationary – Cross from Horizon to Horizon while in use.Height varies with purpose.

• Low Earth Orbit (LEO)400-1200 miles

• Medium Earth Orbit (MEO)12,000 miles (GPS)

• Some Systems Must Maintain a Minimum of 2-3 Satellites in View at All Times

Satellite System Antenna Types

• Wide Variety of Marine Communication Needs• Receive Only

– GPS, Weather, TV, Other Entertainment

• Transmit/Receive– Voice/Fax– Internet Data Services– Video Conferencing

• Motion Compensated Systems


GPS Antenna Installations

• Must have a clear view of the sky

• Must be outside Radar Beam, either above or below

• Should be below SATCOM Antenna Beam

• Cell Transmissions Can Interfere with GPS Reception


Typical Satellite System

Above Deck

Below Deck

Interface is dependent on Satellite Dome & System

Satellite Dome Location

• Physically Secure Location• Communications are Line-of-sight

– Clear View of as Much Sky as Practical

• Follow Antenna Spacing Requirements• Outside Any Radar Array by 6 Feet


Multi-path Interference

• Paths Arrive at Different Times• Received Signal is Summation of

All Signals Received

DirectEcho 1Echo 2Signal


Orientation and Location

Antenna UnitAntenna Unit

O X

°15Antenna UnitAntenna Unit °15Antenna UnitAntenna Unit

O X

Flat Surface

No Obstacles


Effect of Misalignment

• Misalignment Moves Predicted Satellite Position– 30 Second Normal Search Time– 2 to 5 Minute Search Time when Misaligned– Systems with both position & heading inputs are typically

faster

45 °

Line-of-Sight

-15° to+85°

BlockedFrom View!

Mast or CabinStructure

-15° to +115°


Satellite DomeRadar Clearance

±15°

• Average Radar Antenna has a vertical beamwidth of ±20°

±10°

System Grounding

• 10 AWG or larger Ground wire

• Connect dome and Control Unit to RF Ground

• Run wire to Local RF Ground Bus


Summary

• Antenna characteristics are determined by physical construction

• Practical Considerations Drive Mounting Locations

• Mounting options vary from vessel to vessel• Poor location can affect antenna performance


Marine Antenna Installations - NMEA antenna installations ibex... · Antenna Basics VHF, SSB,...

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