Upload
douglas-rice
View
214
Download
0
Tags:
Embed Size (px)
Citation preview
ES
Teem
Tra
inin
g
Cla
ssAntenna Fundamentals
Decibels (dB)Decibels (dB)
• Used for all mathematical calculations in the radio world.– dB is a logarithmic number
• dB =10 log (linear number)– A gain of 2 = 10 log (2) = 3 dB– A gain of 4 = 10 log (4) = 6 dB– When a number doubles it goes up 3 dB– When a number reduces by 1/2, it goes down -3 dB
– To multiply linear numbers you add logarithms– To divide linear numbers you subtract logarithms
Antenna GainAntenna Gain
• Antenna Gain measure in decibels (dB)– Double every 3 dB
• Effective Radiated Power (ERP) = Tx Power + Antenna Gain - Feedline Losses
• Received Signal = Rx Power + Antenna Gain - Feedline losses
• As Antenna Gain increases Antenna Pattern becomes more directional
RF EnergyAntennaTop View
Radiation PatternsRadiation Patterns
• Omni-Directional – Radiates RF energy in all directions from antenna
Top ViewRadiation Pattern
Vertical Polarization
360 degrees
Side ViewRadiation Pattern
Vertical Polarization
Omni-directional Antenna Vertical Polarized
RF Basics - Omni-Directional AntennasRF Basics - Omni-Directional Antennas
• Omni-Directional Antenna– Radiates RF energy in all directions from antenna– Usually used at the Master and Repeater Nodes
• As Antenna Gain increases the Antenna Pattern becomes more directional
Omni- Directional Antenna Shown Below
Side ViewRadiation Pattern
Vertical Polarization
3 dB Points
Vertical Beam Width (degrees)
RF Basics - Antenna GainRF Basics - Antenna Gain
Top ViewRadiation Pattern
Vertical Polarization
360 degrees
Remains Unchanged
Radiation Patterns
• Directional– Compresses RF Energy in one direction
AntennaTop View
RF Energy
Horizontal Beam Width
(degrees)
Back Lobe
Top View Radiation Pattern
Vertically Polarized
3 dB Points
Side View Radiation Pattern
Vertically Polarized
Vertical Beam Width
(degrees)
Back Lobe
3 dB Points
RF Basics - Directional AntennasRF Basics - Directional Antennas
• Directional – Radiates RF energy in one direction– Usually used at Remote Nodes in a Point to Multi-
point system or Point to Point Site
RF Basics - Antenna GainRF Basics - Antenna Gain
• As Antenna Gain increases the Antenna Pattern becomes more directional
Top View Radiation Pattern
Vertically Polarized
Back Lobe
3 dB Points
Side View Radiation Pattern
Vertically Polarized
3 dB Points
Back Lobe
Vertical Beam Width (degrees)
Directional Antenna Shown Below
Horizontal Beam Width (degrees)
Directional Antenna Vertical Polarized Omni-directional Antenna
Vertical Polarized
Antenna PolarizationAntenna Polarization• Vertical Or Horizontal Polarization
– Polarization is the radiating element referenced to earth
– All nodes must be the same polarization• Cancellation of signal if mismatched
– Vertical Polarization for Most Radio Applications• Mixture of Omni and Directional Antennas• No Horizontal Polarization of Omni-Directional
Antenna TypesAntenna Types
• 1/2 Wave Antenna– Close to Isotropic Radiation– Approximately 3 dB gain– No ground planes needed
Cone of Silence
Cone of Silence
Antenna TypesAntenna Types
• 1/4 Wave Antenna– Unity Gain– Requires Ground Planes– “Cone of Silence” above
and below antenna
Antenna TypesAntenna Types
• Yagi– High gain– Directional– Horizontal Beamwidth– Vertical Beamwidth
Antenna ImpedanceAntenna Impedance
• 50 Ohm Load Is the Industry Standard– Based on 1/4 Wave Antenna
• Antenna Impedance Must Match Feedline Impedance and Transmitter Output Impedance– A Mismatch Will Induce Standing Waves Which Will
Reduce Radiated Power
RF Basics - FeedlinesRF Basics - Feedlines
• Feedline– Pipeline for RF Energy From Radio to/from Antenna – Different Cable Types Have Different Losses
• The lower the loss the more expensive the cable– Losses Based Upon Length & Frequency
• Expressed in dB/100 ft. by the manufacturer – The higher the frequency, the more attenuation in
cables, connectors, etc.– All feedlines and connectors induce losses to RF
energy
RF Basics - Feedline Attenuation TableRF Basics - Feedline Attenuation Table
Frequency Band (MHz) 66 to 79 150 to 174 400 to 420 450 to 470 900 to 940 2400 to 2500 5100 to 5400
RG-58 2.5 5.2 8.4 9 13.7 n/a n/a
LMR 195 2 4.4 7.8 7.8 11.1 19 29.9
RG-8 (Solid) 1.1 1.7 2.9 3 4.5 7 14
LMR 600 0.547 0.964 1.72 1.72 2.5 4.42 7.3
3/8" Heliax 0.084 1.48 2.48 2.64 3.97 6.47 10.2
1/2" Heliax 0.463 0.88 1.36 1.45 2.17 3.52 5.5
7/8" Heliax 0.254 0.486 0.758 0.808 1.23 2.02 3.4
Feedline Attenuation (- dB/100 ft.)
Types of FeedlinesTypes of Feedlines
• RG-58 Cable– Only use on very short runs (< 10 feet)– Good on licensed (<1 GHz) only– Very flexible
• 72-79 MHz = 3.8 dB per 100 feet• 150-174 MHz = 5.2 dB per 100 feet• 400-500 MHz = 11 dB per 100 feet
Types of FeedlinesTypes of Feedlines
• LMR-195 Cable– Only use on very short runs (2.5 foot standard length)– Very flexible– Good up to 2.4 GHz
• 72-79 MHz = 3.0 dB per 100 feet• 150-174 MHz = 4.4 dB per 100 feet• 400-500 MHz = 7.8 dB per 100 feet• 2.4 GHz = 19 dB per 100 feet
Types of FeedlinesTypes of Feedlines
• RG-8 Cable– Good for feedline runs up to 50 feet (Licensed
Radios)– Workable losses up to UHF frequencies
• 72-79 MHz = 1.5 dB per 100 feet• 150-174 MHz = 2.3 dB per 100 feet• 400-500 MHz = 4.4 dB per 100 feet• 2.4 GHz = 10 dB per 100 feet
– Both rigid and flexible cable available
Types of CoaxTypes of Coax
• 1/2 Inch Heliax– Recommend for feedline runs over 50 feet– Very low loss
• 72-79 MHz = .6 dB loss per 100 feet• 150-174 MHz = .8 dB per 100 feet• 400-500 MHz = 1.5 dB loss per 100 feet• 2.4 GHz = 3.74 dB loss per 100 feet
– Very rigid– Higher cost per foot than RG-8
Connector TypesConnector Types
• TNC– Input connectors on most ESTeems
• UHF – Input to most antennas
• N-Type– Input to lightning arrestor and some antennas
• Reverse Polarity– All unlicensed radio systems require “unique”
connectors
Standing Wave Ratio (SWR)Standing Wave Ratio (SWR)
• Ratio of Maximum to Minimum Values in Standing Wave Pattern– Voltage (VSWR) or Current
• Mismatch in Impedance (Antenna or Cable) Will Induce Standing Waves
• Measurement of Forward and Reflected Power Most Field Expedient – Wattmeter
To Antenna
Directional Watt Meter
Transceiver
SWR MeasurementSWR Measurement
• Maximum = 10% Reflected Power
• ESTeem commands– Radio ON command for serial– Advanced Menu 195E
Lightning Arrestor
12 VDC Power Supply
User’s Device
Feedline
Antenna
Interface Cable
Typical Outdoor Antenna Block DiagramTypical Outdoor Antenna Block Diagram
Typical Indoor/Mobile Antenna DiagramTypical Indoor/Mobile Antenna Diagram
12 VDC Power Supply
User’s Device
Feedline
Antenna
Interface Cable
Typical Model 195E Mounting Typical Model 195E Mounting
Model 195ESeries
Omni-Directional Antenna
Model 195E Outdoor Fixed Base Hardware
Diagram
Direct Pole MountPole Mounting Kit EST P/N AA195PM
Power Over Ethernet Cable
Ethernet CAT-5e Cable 300 ft. maximum
Unit Shown With Rubber Duct Antennas
Weather Proof Boot
Weather Proof Front Cover
Antenna Feedline
External Antennas
Directional Antennas
Weather Proof Boot
Weather Proof Boot
Direct Mount Antennas
To LAN Interface
PoE Power Supply EST P/N AA175
Ethernet Surge Protection
EST P/N AA166
Ethernet CAT 5e Cable
EST P/N: AA09.2
RF Filters (Licensed Frequencies)RF Filters (Licensed Frequencies)
• Bandpass Filter– Filters out all radio frequencies except the operating
frequency
• Notch Filter– Filters out a specific frequency in the frequency band
• Combiner/Duplexer– Allows two transceivers to share a common antenna
and coax– Minimum frequency separation
Mobile InstallationMobile Installation
• Antenna Uses Vehicle as Ground Plane
• No Lightning Arrestor Needed
• Antenna Pattern Dependent On Vehicle Mounting Location
DC Grounded Antenna
Multi-Strike Lightning Arrestor
Earth Ground
Lightning ProtectionLightning Protection
• Ground Antenna and Lightning Arrestor to Same Ground Potential
• Protect Power Supply
• Protect Data Cable
Weather ProofingWeather Proofing
• Silicone On Connector Threads– Do not get sealant on center conductor
• Wrap RF Connector With Electrical Tape– Wrap beyond the connector of easy removal
• Form Vinyl Mastic Pad Over Connection
• Coat Entire Connector With Skotchkote Electrical Coating