Marine Antenna Installations IBEX 2011 Speakers: David Gratton- Martek-Palm Beach, FL Johnny Lindstrom- Westport Shipyard, WA 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 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) Property of the NMEA. Shall not be copied or re-distributed.
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. Property of the NMEA. Shall not be copied or re-distributed.
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 • Property of the NMEA. Shall not be copied or re-distributed.
Antenna Spacing (Feet) VHF GPS SSB Radar Cell Sat TV 4 3 3 2 2 3 VHF 3 1/2 4 (a) 5 (c) 3 GPS 3 4 10 4 2 4 SSB 2 (a) 2 2 1 4 Radar 2 5 (c) 2 1 1 4 Cell 3 3 4 4 4 6 Sat TV Property of the NMEA. Shall not be copied or re-distributed.
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
Antenna Locations
Antenna Locations
Radiation Pattern Example VHF, AM/FM, AIS, Cellular 90 75 60 45 30 15 0 3D View Top Down View Property of the NMEA. Shall not be copied or re-distributed.
High & Low Gain Patterns Low Gain High Gain
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) Property of the NMEA. Shall not be copied or re-distributed.
Aperture Disturbances VHF, 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 Property of the NMEA. Shall not be copied or re-distributed.
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 Property of the NMEA. Shall not be copied or re-distributed.
VHF Test Parameters Test Measurement Nominal Value Tolerance 1 RF Forward Power 25 Watts ≥ 20 Watts 2 RF Reflected Power 0 Watt ≤ 3 Watts at DUT Output 3 Voltage at DUT 13.6 Volts ≥ 12 Volts Input DUT= Device Under Test Property of the NMEA. Shall not be copied or re-distributed.
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 Weight Property 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 1 Watt ≤ 5 Watts at DUT Output 3 Signal strength meter required to measure antenna output 3 Voltage at DUT 13.6 Volts ≥ 12 Volts Input
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) Property of the NMEA. Shall not be copied or re-distributed.
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 Property of the NMEA. Shall not be copied or re-distributed.
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. Property of the NMEA. Shall not be copied or re-distributed.
Wind & Weather Sensors: Dead Air Zone
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) 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 Property of the NMEA. Shall not be copied or re-distributed.
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 • Property of the NMEA. Shall not be copied or re-distributed.
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 Property of the NMEA. Shall not be copied or re-distributed.
Multi-path Interference • Paths Arrive at Different Times • Received Signal is Summation of All Signals Received Direct Echo 1 Echo 2 Signal Property of the NMEA. Shall not be copied or re-distributed.
Orientation and Location Flat Surface Antenna Unit Antenna Unit O X No Obstacles Antenna Unit Antenna Unit ° 15 Antenna Unit Antenna Unit ° 15 O X Property of the NMEA. Shall not be copied or re-distributed.
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 -15° to +115° +85° Blocked From View! Mast or Cabin Structure Property of the NMEA. Shall not be copied or re-distributed.
Satellite Dome Radar Clearance ±10° ±15 ° • Average Radar Antenna has a vertical beamwidth of ±20°
System Grounding • 10 AWG or larger Ground wire • Connect dome and Control Unit to RF Ground • Run wire to Local RF Ground Bus Property of the NMEA. Shall not be copied or re-distributed.
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