2010 Edition Confidential RSI Corporation
Antenna 101 BasicsAntenna 101 Basics
2010 Advance Train the 2010 Advance Train the TrainerTrainer
Starts @ 0800Starts @ 0800
• A fairly small amount of information and educational material can go a long way toward preventing unnecessary alarm or concern to workers and others.
• Consider making some basic educational material available to anyone who wants it, not just those who need it.
20010 Edition Confidential RSI Corporation
2010 Edition Confidential RSI Corporation
MPE MathMPE MathAdvance Train the TrainerAdvance Train the Trainer
2010 Edition Confidential RSI Corporation
First things first…First things first…
It is a It is a SafetySafety issue! issue!
You can calculate the length of the You can calculate the length of the snake, and how far to stay away, but snake, and how far to stay away, but if it bites you, it bites you!if it bites you, it bites you!
Is RF Radiation a Is RF Radiation a technicaltechnical issue or a issue or a SafetySafety issue? issue?
2002 Edition Confidential RSI Corporation
More Information,More Information,We added last night after Train The We added last night after Train The
Trainer!Trainer!
DB what is it????
Radio waves
2010 Edition Confidential RSI Corporation
• STANDARDS FOR ANTENNA GAIN AND LOSS MEASUREMENTS INCLUDE: dB The universal unit of measure, named after Alexander Graham Bell. The dB is a Decibel or 1/10 of one bell. Mathematically, if can be expressed in many ways,
• Watts: Output power or magnitude - using voltage, current and resistance as parameters. Volts X Amp =W
• dBi: Gain with reference to the Isotropic Radiator. A very popular reference in Wi-Fi antenna systems and other applications using the 802.11 standard.
• dBd: Gain reference to a dipole about 2 db• dBm The ratio of two powers referenced to 1mw (0.001Watt). •
2010 Edition Confidential RSI Corporation
2010 Edition Confidential RSI Corporation
MPE MathMPE MathRadio waves travel at the speed of lightRadio waves travel at the speed of light
186,000 miles per second = 186,000 miles per second = 300,000300,000 kilometers per secondkilometers per second
λ
One Hertz equals one full cycle per second
wavelength
TX
2010 Edition Confidential RSI Corporation
meters = centimeters * .01
meters = inches * .0254
meters = feet * .3048
centimeters = meters * 100
feet = meters * 3.28
inches = meters * 39.37
millimeters = meters * 1000
uW = mW * 1000
mW = uW * .001
EIRP = ERP x 1.64
dBi = dBd + 2 or dB + 2
W/m2 = 10(mW/cm2)
mW/cm2 = W/m2
10
MPE MathMPE Math
2010 Edition RSI Corporation
MPE MathMPE Math
Industry standard forhalf wave dipole in ft.
λ = 492 MHz
Wavelength from Frequency
λ = wavelengthf = frequency (in MHz)
Problem 1: Find wavelength of 450 MHz
30000 = 66.66 cm = 2.19 ft 450
2010 Edition RSI Corporation
MPE MathMPE Math
Frequency from Wavelength
Problem 2: Find frequency (resonance) of someone 6 ft tall.
6 ft = 182.9 cm
f = 30000 = 164 MHz 182.9
λ = 164 λ = 82 MHz Isolated = 41 MHz Grounded
Resonance
2010 Edition RSI Corporation
Gain is realGain is real
Note: See FCC OET 65 for aperture (dish) antenna equations
Estimate of power from gain can be achieved by the following method:The power doubles for every 3 dB of gain0 dB = 5 Watts 18 dB = 320 Watts3 dB = 10 Watts 21 dB = 640 Watts6 dB = 20 Watts 24 dB = 1280 Watts9 dB = 40 Watts 27 dB = 2560 Watts12 dB = 80 Watts 30 dB = 5120 Watts15 dB = 160 WattsSo 5 watts into a MW antenna with 30 dB gain would
Eventually become 5120 Watts in the far field of the antenna
Student ExerciseStudent Exercise
ANTENNA GAIN
2010 Edition RSI Corporation
Student Exercise Worked Student Exercise Worked Example: Example:
• Gain (dB) = 7.5 +20log(6) + 20log(6.5) Gain (dB) = 7.5 +20(0.7781) + 20(0.8129) = Gain (dB) = 7.5 +15.56 + 16.25 Gain (dB) = 39.31
2010 Edition Confidential RSI Corporation
TO MUCH MATH, for most!!!
2002 Edition Confidential RSI Corporation
Student Exercise Antenna Gain is measured in dB with reference to the Isotropic Radiator. The compounded gain of the antenna, plus the output of the transmitter is the basis for the EIRP or ERP power measurement. When using parabolic antennas with fixed dish sizes, we can calculate the gain or use a chart giving the antenna gain with respect to an Isotropic antenna.
MPE MathMPE Math
4 Bay antenna (6 dBd gain) @ 162 MHz WX Radio & 1000 watts into the antenna =
4000 watts
Near field Far field
Radio wave continues toincrease in power densityover distance with gain ant.
Radio wave decreases inpower density over distance
Max Gain
2010 Edition Confidential RSI Corporation
MPE MathMPE Math
FCC OET 65 Power Density CalculationsFar field only without ground reflections
S=power density in appropriate units (i.e. mW/cm2)P=power input to antenna in mWG= numeric power gain of antenna in direction of interest R (or D)= distance to the center of radiation of antenna
Frii’s Equation S= PG_ 4R2
More Field StrengthMore Field Strength• Ground reflections can double the field
strength and cause a four-fold increase in power density. For low mounted antennas on rooftops reflections must be included, take 4 out of the denominator
• S= PG/ R2
2010 Edition RSI Corporation
Double the field strength will Double the field strength will cause a four-fold increase in cause a four-fold increase in
power density (MPE).power density (MPE).
2010 Edition From the ½ day BPM Class RSI Corporation
From the “BMP Class”
Gain is realGain is real
RF power doubles for every 3 dB of gain
Every time the field strength doubles there is a four fold increase in power density (MPE)
From your ½ day BMP book
Frequency and Frequency and WavelengthWavelength
CONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATION
Frequency in kHz:Frequency in kHz: (300,000) / (300,000) / wavelength in meters.wavelength in meters.
Frequency in MHz:Frequency in MHz: (300) / (300) / wavelength in meters.wavelength in meters.
Frequency in MHz:Frequency in MHz: (984) / (984) / wavelength in feet.wavelength in feet.
Wavelength in meters:Wavelength in meters: (300,000) / (300,000) / frequency in kHz.frequency in kHz.
Wavelength in meters:Wavelength in meters: (300) / (300) / frequency in MHz.frequency in MHz.
Wavelength in feet:Wavelength in feet: (984) / (984) / frequency in MHz.frequency in MHz.
2010 Edition Confidential RSI Corporation
Numeric Gain vs Logarithmic Power Gain
G = 10 Example:dBi = dBd +23db = 5dBi
G = 10 G = 10.5 = 3.16 Gain
Unity = 2 dBi = 1.58 Gain3 dB = 5 dBi = 3.16 Gain12 dB = 14 dBi = 25.12 Gain
MPE MathMPE Math
dBi10
5 10
0.3 1 3 10 30 100 300 1 3 10 30 1000.3 1 3 10 30 100 300 1 3 10 30 100 0.3 1 3 10 30 100 300 1 3 10 30 1000.3 1 3 10 30 100 300 1 3 10 30 100
MHzMHzMHzMHz GHzGHzGHzGHz
100100100100
1111
5555
.2.2.2.2
mWmW/cm/cm22
mWmW/cm/cm22
AM Radio FM
MPE LAW
Controlled 100%Controlled 100%
Uncontrolled
FCC RulemakingFCC RulemakingFCC RulemakingFCC Rulemaking
Check Both E&H< 300MHz
6 Min TWA
30Min TWA
Cell phones
20ontrolled reading is OSHA’S ACTION LIMIT
OSHA ACTION LIMITOSHA ACTION LIMIT
PCS
2.4 wireless
MW
2010 Edition Confidential RSI Corporation
MPE MathMPE MathPower Density CalculationsFar field only without ground reflections
For this example, 150 MHz, 100W with 6 dB gain antenna, 20 feet (609.6 cm) away from adjacent tower.6 dB must be changed to numerical gain100 W = 100,000 mW
Numeric Gain, G= 10^dBi = 10 .8 = 6.3 Gain 10S = PG_ = 100,000 * 6.3 = 630,000 = 630,000 4 R2 4 R2 12.57(371612) 4,671,165 =0.135 mW/cm2
The uncontrolled limit for 150 MHz is 0.2 mW/cm2, so NO PROBLEM!!.135/ .2=67.5%
2010 Edition Confidential RSI Corporation
MPE MathMPE MathPower Density CalculationsFar field only with ground reflections
For this example, 150 MHz, 100W with 6 dB gain antenna, 20 feet (609.6 cm) away on rooftop level.
Numeric Gain, G= 10^dBi = 10 .8 = 6.3 Gain 10S = PG_ = 100,000 * 6.3 = 630,000 = 630,000 R2 R2 3.14(371612) 1,166,862 =0.54 mW/cm2
The uncontrolled limit for 150 MHz is 0.2 mW/cm2, so it is a PROBLEM!!.54/ .2=270%
Vehicle-mounted antennas Vehicle-mounted antennas from the FCC RFR Web page from the FCC RFR Web page
May 2010May 2010• Vehicle-mounted antennas used for wireless
communications normally operate at a power level of three watts or less. These wireless antennas are typically mounted on the roof, trunk, or rear window of a car or truck.
•
2010 Edition Confidential RSI Corporation
• FCC Results of Studies may 2010 • Show that, in order to be exposed to RF levels
that approach the safety limits it would be necessary to remain very close to a vehicle-mounted wireless antenna for a significant amount of time. The metal body of the vehicle can effectively shield occupants.
• Proper installation of a vehicle-mounted antenna to maximize this shielding effect is a good way to minimize exposure. The antennas should be installed either in the center of the roof or center of the trunk of a vehicle.
2010 Edition Confidential RSI Corporation
2010 Edition Confidential RSI Corporation
Antenna 101Antenna 101
In order to work safely in an RF environment,it is a good idea to know what frequencies you are exposed to, as the MPE limits are based on frequency and the relationship of the wavelength to the body or its parts.
CONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATION
The Higher the Frequency the Shorter the Wave
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Cellular or PCS Antenna
VerticalAntenna
(paging, etc.)
GroundplaneAntenna
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Cellular Antenna
Microwave ParabolicAntenna
General Rule: Cellular/LTE 700-900 MHz, PCS 1.9-2.4 GHz
THE 1THE 1stst PANEL PANEL
ANTENNA!ANTENNA!
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Circularly Polarized Dipole Antenna
Satellite Receive Dish
Circularly Polarized BC Antenna
Length of an AntennaLength of an Antenna
• Quarter-wave antenna:Length in feet = 234 / frequency in MHz.
• Half-wave antenna:Length in feet = 468 / frequency in MHz.
CONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATION
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Low Band 30-54MHz 9-16.0 ft. 4.5-8.0 ft.
VHF 140-174 MHz 3 ft. 1.5 ft.
UHF 400-512 MHz 1 ft. 6 in.
900 MHz 6 in. 3 in.
Frequency Ranges Approx. Full Element Approx. Length from Length (1/2 wave) Center (1/4 wave)
Antennas vary greatly: this is a rough guide to ID-ing frequencies
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft.
VHF 3 ft. 1.5 ft.
UHF 1 ft. 6 in.
900 MHz 6 in. 3 in.
For Verticals w/ reflectors,Note the length of the reflecting element
Length (1/2 wave) Center (1/4 wave)
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
VHF
Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft.
VHF 3 ft. 1.5 ft.
UHF 1 ft. 6 in.
900 MHz 6 in. 3 in.
½ wave ¼ wave
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft.
VHF 3 ft. 1.5 ft.
UHF 1 ft. 6 in.
900 MHz 6 in. 3 in.
UHF
½ wave ¼ wave
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft.
VHF 3 ft. 1.5 ft.
UHF 1 ft. 6 in.
900 MHz 6 in. 3 in.
900 MHz
½ wave ¼ wave
30 MHz30 MHz VHF (30-300 MHz)VHF (30-300 MHz)Body WavelengthBody Wavelength
9 to 1 ½ feet!9 to 1 ½ feet!
VHF (30-300 MHz)VHF (30-300 MHz)Body WavelengthBody Wavelength
9 to 1 ½ feet!9 to 1 ½ feet!At frequencies between 30 and 300 At frequencies between 30 and 300 MHz, the human body’s characteristics MHz, the human body’s characteristics lend themselves to being a good lend themselves to being a good antenna, where:antenna, where:
The body and its parts experience The body and its parts experience maximum absorption and therefore maximum absorption and therefore acts like an antenna, resonating with acts like an antenna, resonating with the frequency.the frequency.
The Specific Absorption Rate The Specific Absorption Rate influences the body’s ability to cool influences the body’s ability to cool after exposure.after exposure.
The absorption rate decreases rapidly The absorption rate decreases rapidly at frequencies above 300 MHz.at frequencies above 300 MHz.
300 MHz 300 MHz
CONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATIONCONFIDENTIAL R.S.I. CORPORATION
ANTENNA 101
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Folded DipoleFolded Dipole
2002 Edition Confidential RSI Corporation
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
Yagi Yagi AntennaAntenna
General Rule: 6MHz VHF to 2.4GHz Frequency Range
450MHz
2002 Edition Confidential RSI Corporation
6-30MHz
2010 Edition Confidential RSI Corporation
3’long = 150MHZ
950 MHz STL
2002 Edition Confidential RSI Corporation
2002 Edition Confidential RSI Corporation
3 Meter wave 100MHz FM100The loops are 1 ½ meters ½ wave antenna
100,000 watts- 8 DB =High MPE
2002 Edition Confidential RSI Corporation
2002 Edition Confidential RSI Corporation
2002 Edition Confidential RSI Corporation
HIGH POWER
4ft loopsWhat type of antenna?
UHF 51-59 to cell/phone TV
UHF 51-59 to cell/phone “TV” up to 50,000 watts
RF Antennas 101RF Antennas 101
The Lines in this Photo are from High RF in the area.
50,000 watts
Large BDA SystemLarge BDA System
Open Waveguide Leak
Are there Are there RF LEAKSRF LEAKSin the your in the your
Equipment Rooms? Equipment Rooms?
AM TowersAM Towers
• The whole tower is the antenna (1/4 wave used widely)• Some are Non-directional• Other are using more than one tower and are directional • Some or Day time only• Other 24/7 but change power levels• Very High Current Hazard (MPE hazard lower on 500
and 1000 watt stations) with re-radiation hotspots• Must have a plan to “lock-out” when on the tower
(Insulated base on most towers)
Page 11
AM Broadcast Three Tower AM Broadcast Three Tower DirectionalDirectional
5000 watt 780KHz with the city east of the towers
AM Broadcast Three Tower AM Broadcast Three Tower DirectionalDirectional
Non-directional AM Non-directional AM BroadcastBroadcast
AM
New Tower Added¾ of a mile SE
360 D
AM BroadcastAM Broadcast
• The FCC requires that AM Broadcast sites have Proof measurements to determine the pattern
I work with ________ Raleigh, NC. I’ve got a question about climbing a tower that is next to four AM towers. I can’t get a straight answer from the tower owner. We need to do a work on this tower. Photos of the tower are attached. Is this tower safe to climb? or how can we check to see if the tower is safe to climb? Your advise would be appreciated.
Thanks,
I work with ________ Raleigh, NC. I’ve got a question about climbing a tower that is next to four AM towers. I can’t get a straight answer from the tower owner. We need to do a work on this tower. Photos of the tower are attached. Is this tower safe to climb? or how can we check to see if the tower is safe to climb? Your advise would be appreciated.
Thanks,
Email from a worker
2002 Edition Confidential RSI Corporation
?
What is wrong in this photo?
2010 Edition Confidential RSI Corporation
Antennas 101Antennas 101
That’s That’s All All Folks!Folks!Questions and Answers
Take RSI’s Introduction to
“RAS” Radio Antenna Systems 1-3
To learn more
2010 Edition Confidential RSI Corporation
Any Questions?Any Questions?