Marine Antenna Installations

Transcription

1 Marine Antenna Installations IBEX 2011 Speakers: David Gratton- Martek-Palm Beach, FL Johnny Lindstrom- Westport Shipyard, WA

2 Seminar Overview Antennas AIS, Cellular, Radar, Satellite, SSB, VHF, WX Location Aesthetic vs. Practical vs. Customer Requests Testing Installations

3 Antenna Basics VHF, 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)

4 Antenna Locations VHF, 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.

5 Antenna Spacing Important Notes 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

6 Antenna Spacing (Feet) VHF GPS SSB Radar Cell Sat TV VHF GPS 3 1/2 4 (a) 5 (c) 3 SSB Radar 2 (a) Cell 2 5 (c) Sat TV

7 Antenna Types Application Description T or R Type VHF Communication T/R Dipole Sideband (SSB) Communication T/R Marconi AM/FM Entertainment R Dipole AIS Vessel Tracking R Dipole Cellular Communication T/R Dipole GPS Navigation R Micro strip Satellite Comm. Communication T/R Parabolic Satellite TV Entertainment R Parabolic Radar Collision Avoidance T/R Reflector Weather Environment R Micro strip

8 Antenna Locations

9 Antenna Locations

10 Radiation Pattern Example VHF, AM/FM, AIS, Cellular D View Top Down View

11 High & Low Gain Patterns Low Gain High Gain

12 Antenna Gain VHF, 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)

13 Aperture Disturbances VHF, SSB, AM/FM, AIS, Cellular Aperture Size Is a Function of Wavelength 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

14 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

15 VHF Test Parameters Test Measurement Nominal Value Tolerance 1 RF Forward Power 25 Watts 20 Watts 2 RF Reflected Power at DUT Output 3 Voltage at DUT Input 0 Watt 3 Watts 13.6 Volts 12 Volts DUT= Device Under Test

16 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

17 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 Weight

18 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 3Signal strength meter required to measure antenna output 3 Voltage at DUT Input 13.6 Volts 12 Volts

19 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

20 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)

21 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

22 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.

23 Wind & Weather Sensors: Dead Air Zone

24 Satellite Constellation Geometry Geostationary Always in Same Relative Position in Sky. TV, Communications, Weather 22,000 miles Non-stationary Cross from Horizon to Horizon while in use. Height varies with purpose. Low Earth Orbit (LEO) miles Medium Earth Orbit (MEO) 12,000 miles (GPS) Some Systems Must Maintain a Minimum of 2-3 Satellites in View at All Times

25 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

26 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

27 Typical Satellite System Above Deck Below Deck Interface is dependent on Satellite Dome & System

28 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

29 Multi-path Interference Paths Arrive at Different Times Received Signal is Summation of All Signals Received Direct Echo 1 Echo 2 Signal

30 Orientation and Location Flat Surface Antenna Unit O X No Obstacles Antenna Unit Antenna Unit O X

31 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

32 Line-of-Sight to to Blocked From View! Mast or Cabin Structure

33 Satellite Dome Radar Clearance ±15 ±10 Average Radar Antenna has a vertical beamwidth of ±20

34 System Grounding 10 AWG or larger Ground wire Connect dome and Control Unit to RF Ground Run wire to Local RF Ground Bus

35 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