DEVELOPMENT OF AN RF SAFETY PROGRAM AT A “REMOTE SITE”
Donald L. Haes, Jr., Ph.D., CHP
α
Presented to FLAAPM / FCHPS
November 13, 2015
I am a member of the International Committee on Electromagnetic Safety (ICES)
and the Institute of Electrical and Electronics Engineers (IEEE), including the
Standards Association (IEEE/SA). All opinions expressed in this workshop are my
own, and are not intended to represent those of ICES, IEEE, or the IEEE SA.
Don Haes
2
Lets go back to the early 1990s …
ANSI C95.1-1991 just released with two-tiered exposure limits; prior to that there was a single-tier with frequency dependent limit values.
Some concerns were raised about a “remote site with powerful radars blasting everyone on the soccer field.”
The site was under the direction of MIT’s Lincoln laboratory, but in the Republic of the Marshal Islands; Kwajalein Atoll.
2
Location of “remote site” 3
Kwajalein Atoll is a crescent loop of coral reef enclosing an area of 1,100 square miles ; the world’s largest lagoon. Situated on the reef are approximately 100 small islands with a total land area of 5.6 square miles. Kwajalein Island, the largest in the atoll, is one-half mile wide and three miles long (approximately 1.2 square miles in area). From Kwajalein Island to Roi-Namur, in the north, is about 50 miles.
5
Inhabitants of “remote site”? 6
Inhabitants of “remote site”!
U.S. Army Kwajalein Atoll (USAKA): The islands of Kwajalein’ and Roi-Namur host >2,400 residents (military personnel, Army civilians, contractor employees, tenants, and family members.
Home to (now) Ronald Reagan Ballistic Missile Defense Test Site at Kwajalein Atoll (RTS), operates as a subordinate command of the U.S. Army Space and Missile Defense Command.
Approximately 12,000 Marshallese citizens live within the atoll, with the majority living on Ebeye.
7
U.S. ARMY KWAJALEIN ATOLL
Inhabitants of “remote site”; USAKA
Kwajalein
Roi-Namur
6
Launch and tracking of space vehicles
The launch of Flight 5 of the SpaceX Falcon 1 rocket from Omelek Island on Kwajalein Atoll 7/13/2009. (Photo courtesy of USAKA/RTS).
9
For many years, KREMS has played a role in collecting data associated with intercontinental ballistic missile testing and space tracking Kiernan Re-Entry Measurement Site (KREMS) radars.
Inhabitants of “remote site”; civilian population 9
Ebeye
3rd island
11
“In one historic week, Jan. 29 to Feb. 4, 1944, with the most
powerful invasion force ever assembled up to that time, American
forces seized Kwajalein Atoll from Japan. The invasion of the
Marshall Islands, code named Operation Flintlock, served as a
model for future operations in the Pacific. The seizure of Kwajalein
Atoll was the first capture of pre-war Japanese territory and
pierced the Japanese defense perimeter, paving the road to Tokyo.”
12 Battle plans; circa 1942
13
RFR Sources at remote site? 14
Lincoln Space Surveillance Complex, Westford, MA
HAY
HAX
Zenith MISA MHR
Telescope/Laser
Lincoln Space Surveillance Complex Sensors*
Millstone UHF Radar (MISA)
Frequency: 440 MHz
Antenna Diameter: 45.5 m
Peak Power: 2.5 MW Beamwidth: 1.1°
Mission: Ionospheric Studies
(Incoherent Scatter)
Since: 1978 Zenith
MISA
Millstone UHF Radar (Zenith)
Frequency: 440 MHz
Antenna Diameter: 67.1 m
Peak Power: 2.5 MW Beamwidth: 0.6°
Mission: Ionospheric Studies
(Incoherent Scatter)
Since: 1962
* Courtesy: Millstone Hill Observatory MIT Atmospheric Sciences Group
14
Lincoln Space Surveillance Complex Sensors*
Millstone Hill Radar (MHR) Frequency: 1.295 GHz
Antenna Diameter: 25.6 m
Peak Power: 2.5 MW
Sensitivity: 50 dB (0 dBsm @ 1000 km) Beamwidth: 0.6° Max.
Bandwidth: 8 MHz
Mission: Deep-Space Metric
Since: 1957 / 1962
* Courtesy: Millstone Hill Observatory MIT Atmospheric Sciences Group
15
MHR
Haystack LRIR (HAY) Frequency: 10 GHz
Diameter: 37 m
Peak Power: 250 kW
Sensitivity: 57 dB (0 dBsm @ 1000 km)
Beamwidth: 0.05°
Max. Bandwidth: 1 GHz
Mission: Radioastronomy/Satellite Imaging
Since: 1964
Haystack Auxiliary (HAX) Frequency: 16.7 GHz
Diameter: 12 m
Peak Power: 50 kW
Sensitivity: 39 dB (0 dBsm @ 1000 km)
Beamwidth: 0.1°
Max. Bandwidth: 2 GHz
Mission: Near-Earth Satellite Imaging
Since: 1993
* Courtesy: Millstone Hill Observatory MIT Atmospheric Sciences Group
Lincoln Space Surveillance Complex Sensors*
HAY
HAX
16
RFR Sources at remote site! 18
ALTAIR: tracks ~1300
deep-space orbiting satellites every week.
TRADEX: became operational in
1962 but was not employed for
space missions until 1994 as a substitute for ALTAIR.
25.6 m (84’)
RFR Sources at remote site! 19
Millimeter-Wave (MMW) radar has the
world’s best range resolution radar, and
produces coherent, high-resolution data images of satellites.
ALCOR’s wideband capability was
adapted to satellite imaging and
pioneering work in developing techniques
and algorithms for generating and interpreting radar images.
13.7 m (45’)
12.1 m (40’)
The KREMS “Sensors”: 20
The KREMS “Sensors” Command: 21
Estimation of Potential RF Exposure Special Considerations
Use maximum power, and a pulse width and pulse repetition frequency that will most closely approximate the maximum rated duty factor.
Account for both horizontal and vertical antenna radiation patterns and the appropriate ground reflection factor for that frequency.
Account for axial rotation in azimuth (“spinning”) and elevation (“nodding”).
Assume transmit “on-time” at least the averaging time for the appropriate MPE for that frequency.
22
Complications: Which RF exposure Standard to use? 23
{PRIVATE Freq./Band P pk P ave USAKA 385-3 MASSACHUSETTS REGs. ANSI C95.1-1991
Name
(MHz)
ID
(MW)
(kW)
Restricted
(Ht > 55") (mW/cm2)
Unrestricted
(Ht < 55") (mW/cm2)
440 CMR 5.0
(Workers) (mW/cm2)
105 CMR 122
(Public) (mW/cm2)
Controlled
(Workers) (mW/cm2)
Uncontrolled
(Public) (mW/cm2)
ALTAIR 162 VHF 7.0 100 1.62 1.0 1.0 0.2 1.0 0.2
ALTAIR 422 UHF 5.0 250 4.22 1.41 1.41 0.28 1.41 0.28
TRADEX 1320 L 2.0 143 10 4.40 4.40 0.88 4.40 0.88
TRADEX 2950 S 1.15 20.2 10 5.0 5.0 1.0 9.83 1.97
ALCOR 5670 C 2.25 7.3 10 5.0 5.0 1.0 10 3.78
MMW 35000 Ka 0.034 3.4 10 5.0 5.0 1.0 10 10
* USAKA Regulation 385-3 for restricted areas (access controlled for the exclusion of people less than 144 cm (55”) in stature and unrestricted areas (access not controlled for the exclusion of people less than 144 cm (55”) in stature [USAKA 385-3 Appendix I], regardless of working status.
Conservatism Using Far Field Calculations 24
Estimation of Expected RF Field Strengths
Parabolic Antenna - on axis
Reactive Near Field
Extends only to about ≈ λ / 2 π
λ = C / f {C = Speed of light in a vacuum (3 ∗ 108 m/s)}
25
Estimation of Expected RF Field Strengths (cont…)
Parabolic Antenna - on axis
26
Radiating Near Field (Fresnel Region)
The extent of the Radiating Near Field (Rnf) is:
Rnf = D2 / 4 ∗ λ
The maximum power density (Snf) in the near field is:
Snf = 16 ∗ P ∗ η = 4 ∗ P ∗ η D => Effective diameter of antenna
π ∗ D2 A A => Effective area of antenna
η => Antenna Efficiency (0.5-0.75)
P => Radiated power (Use Pave for personnel hazards
Note: If Snf < MPE, no need to continue.
Parabolic Antenna - on axis
Intermediate Field
The range of the Intermediate Field (Rif) is:
D2 < Rif < 0.6 ∗ D2
4 ∗ λ λ
The power density (Sif) at distance “r” in the intermediate field:
Sif = Snf ∗ ( Rnf )
r
27
Estimation of Expected RF Field Strengths (cont…)
Parabolic Antenna - on axis Far Field Region (Fraunhöfer Region) Note: The phase and amplitude do not
change appreciably with distance. The field has a plane-wave character.
The Far Field Region (Rff) begins at:
Rff > 0.6 ∗ D2
λ
The power density (Sff) at distance r is (use basic inverse-square function):
Sff = G ∗ P = A ∗ P
4 ∗ π ∗ r2 (λ ∗ r)2
Where: G = Antenna gain
P = Effective generated power
A = Effective area of antenna
r = Distance from antenna
28
Estimation of Expected RF Field Strengths (cont…)
ICES/NCRP Rpt #119 S = P ∗ G 4 ∗ π ∗ R2
or:
S = EIRP 4 ∗ π ∗ R2
Where: S = power density (in appropriate units, e.g. mW/cm2). P = power input to the antenna (in appropriate units, e.g., mW). G = power gain in the direction of interest relative to an isotropic radiator. R = distance to the center of radiation (appropriate units, e.g., cm). EIRP = equivalent (or effective) isotropically radiated power. Notes: 1. Use reflection factor of 22 (4) to be conservative, or 1.62 (2.56) for FM frequencies. 2. May use information from antenna radiation patterns if known.
29
Estimation of Expected RF Field Strengths (cont…)
Gain The Gain (G) is the absolute gain expressed as a power function.
Numerically, the Gain is:
G = 10gain/10
If the gain is unknown, it can be closely approximated by:
G = 4 ∗ π ∗ A ∗ η
λ 2
30
Estimation of Expected RF Field Strengths (cont…)
Scanning Correction
Large scanning angle ( φ ):
S = 4 ∗ P ∗ D ∗ 360
π D2 2 π r φ
For
φ ≥ D ∗ 360
2 π r
31
Estimation of Expected RF Field Strengths (cont…)
Scanning Correction
Small scanning angle (Θ ):
S = 4 ∗ P
π D2
For
Θ < D ∗ 360
2 π r
32
Estimation of Expected RF Field Strengths (cont…)
Non-Parabolic Antenna
Radiating Near Field
Rnf = G ∗ λ
4 π r2
Far Field
Rff ≥ 0.6 ∗ G ∗ λ
π r2
Note: Calculate S as before
33
Estimation of Expected RF Field Strengths (cont…)
Antenna Patterns 34
10dB
10dB
Vertical (“E”) Radiation Pattern Horizontal (“H”) Radiation Pattern
Estimation of Expected RF Field Strengths (cont…)
Calculations of Specific RF Safety parameters Each Major RF Source (“Sensor”) 35
Use formula for power density calculation.*
Use appropriate MPE value for frequency band.
Plug and chug; plot values in “percent MPE” over distance. When using MPE(lower tier), distance at 100%MPE represents
distance beyond which nothing would be REQUIRED. When using MPE(upper tier), distance at 100%MPE represents
distance beyond which documented RF safety training and awareness is REQUIRED, and but within which documented RF exposure mitigation is employed.
* Use appropriate ground reflection factor
Results of ONE RF Sensor: ALTAIR 36
Results of ONE RF Sensor: ALTAIR 37
Obstacles for RF Safety Calculations 38
Each Sensor can rotate 180° and transmit below 0° in elevation; Altair to -9°.*
There is a complex local-knowledge-ONLY convoluted “sector-blanking” protocol used to software-prohibit transmissions in certain “sectors” between particular azimuths (e.g. the “flight” sector).
Too many variables for a single plot; need multiple plots.
What about aircraft?
* “Hard stops” (removable bolts) installed to halt the dish at -2°; electronic stops need to be inhibited to transmit below 10°.
38
Aircraft / Sensor Encounter Scenarios
Significant Encounter Scenarios
KREMS Sensor:
Low elevation.
Stationary beam.
Aircraft:
Slow level flight with heading close to sensor line-of-sight (LOS).
Crossing beam at close range or hovering within beam.
39
38
Aircraft & Sensor “Features” KREMS Sensors
Narrow beams
Pulsed
High peak powers
Limited operating hours
Aircraft
Fixed-wing
Single-engine (low speed, short range)
Rotary-wing
Hover in proximity to sensor
39
Aircraft / Sensor RF Exposure Calculation
FIXED-WING
Set beam-crossing angle (), cross-over range (R0), and groundspeed (v).
Compute beam transit average power flux(S), transit time (Ttransit).
Adjust for radar duty cycle (D).
Scale for 30-minute averaging time.
1800,,,, 0030
transittransit
TDvRSvRS
R0
RL
OS
v
RLOS
crossover
(t)
t < 0
< 0 t > 0
> 0
No aircraft structure shielding effect assumed
40
Aircraft / Sensor RF Exposure Calculation
ROTARY-WING
Set position (x,y,z) and dwell time (Tdwell).
Compute power flux (S) at position.
Adjust for radar duty cycle (D).
Scale for 30-minute averaging time.
R0
RL
OS
v
RLOS
crossover
(t)
t < 0
< 0 t > 0
> 0
1800,,,,30
dwelldwell
TDzyxSzyxS
No aircraft structure shielding effect assumed
41
Near-Field Analytic X-Z Map 42
FIXED-WING AIRCRAFT
Exposure levels below C95.1-1991 (public).
Worst-case conditions examined:
Near-stall groundspeed.
Flight-path/RLOS angle only 3°.
Transit of near-field hotspot.
No aircraft structure shielding.
Aircraft / Sensor RF Exposure Conclusions 43
Rotary-wing Aircraft
Exposure levels can exceed C95.1-1991 (public).
Hover must be within antenna cylinder.
Some cases within only a few meters of RLOS.
Dwell for more than ~30 seconds.
FAA Notice to Airmen (NOTAM)
Aircraft / Sensor RF Exposure Conclusions 44
Have THEM get RF field measurements… 46
TRADEX
ALCOR MMW
ALTAIR
MT
Estimation of Expected RF Field Strengths
Technical Considerations to Consider Prior To Obtaining RF Field Measurements
Calculate averaged and PEAK rated power prior to onsite measurements.
Obtain BOTH E and H field measurements 100-300 MHz UNLESS it can be shown the RF field can be properly characterized with one probe.
Use lowest power, and a pulse width and pulse repetition frequency that will remain within the maximum rated load of the equipment (e.g., the probe!).
Remember the probe “sees” the PEAK field, while it shows you the RMS field.
47
Estimation of Expected RF Field Strengths
KREMS Sensor Information:
48
Sensor Name.
Operating Frequency (wavelength).
“Dish” characteristics:
Diameter. Gain. Vertical and horizontal radiation patterns.
Peak Power (PPk) and modulation characteristics.
Pulse Width. Pulse Repetition Frequency.
Estimation of Expected RF Field Strengths
KREMS Sensor Information:
49
CACLUATE:
Extent Of Near Field (R NF).
Maximum Power Density Expected In The Near Field (S NF).
Range At Which Maximum Near Field Power Density Is
Achieved (R pk).
Beginning Of Far Field (R ff).
Power Density At The Beginning Of The Far Field (S @ R ff ).
KREMS Sensor RF Safety Information 50
Sensor
Name
f
(MHz)
Band
ID
Diam.
(m)
Gain
(dB)
λ
(m)
P pk
(MW)
P ave
(kW)
R nf
(m)
S nf
mW/cm2
R pk
(m)
R ff
(m)
S @ Rff
mW/cm2
ALTAIR 162 VHF 45.7 34.7 1.85 7.0 100 282 14.34 226 677 5.03
ALTAIR 422 UHF 45.7 42.4 0.711 5.0 250 735 36.58 588 1763 11.13
TRADEX 1320 L 25.6 48.2 0.227 2.0 143 721 69.94 577 1730 26.35
TRADEX 2950 S 25.6 54.2 0.102 1.15 20.2 1611 13.99 1289 3867 4.20
ALCOR 5670 C 12.1 55.0 0.0529 2.25 7.3 692 12.52 553 1660 5.48
MMW 35000 Ka 13.7 70.1 0.00857 0.034 3.4 5474 4.07 4379 13138 1.18
MMW 95000 W 13.7 70.1 0.00314 0.005 0.5 14937 0.814 11950 35849 0.032
51 Perspective … Altair VHF
Name R nf (m) R ff (m)
ALTAIR VHF 282 677
52 Perspective … Altair UHF
Name R nf (m) R ff (m)
ALTAIR UHF 735 1763
53 Perspective … Tradex S
Name R nf (m) R ff (m)
TRADEX S 1611 3867
54 Perspective … MMW Ka or W
Name R nf (m) R ff (m)
MMW-Ka 5474 13138
MMW-W 14937 36849
55
R nf R pk R ff
Name (MHz) λ (m) ID (m) mW/cm2 %MPE (Cont) %MPE (Uncont) (m) (m) mW/cm2 %MPE (Cont) %MPE (Uncont)
ALTAIR 162 1.85 VHF 282 14.34 1434% 7170% 226 677 5.03 503% 2515%
ALTAIR 422 0.711 UHF 735 36.58 2594% 13064% 588 1763 11.13 789% 3975%
TRADEX 1320 0.227 L 721 69.94 1590% 7948% 577 1730 26.35 599% 2994%
TRADEX 2950 0.102 S 1611 13.99 142% 710% 1289 3867 4.2 43% 213%
ALCOR 5670 0.0529 C 692 12.52 125% 331% 553 1660 5.48 55% 145%
MMW 35000 0.00857 Ka 5474 4.07 41% 41% 4379 13138 1.18 12% 12%
MMW 95000 0.00314 W 14937 0.814 8.1% 8.1% 11950 35849 0.032 0.32% 0.32%
Sensor Frequency S nf S @ Rff
Sensor
KREMS Sensor RF Safety Information
KREMS Sensor RF SAFTEY CHALLENGES 56
MOST (if not all) locations will present near field conditions of non-uniform fields.
Will have to use much lower power levels and or duty cycles to prevent probe overload.
Will be challenged by setting anticipated field levels high enough to be detected above the probe “thermal drift” (ambient temperatures 95-100°F) at each frequency band.
Will have to use shaped probes only to account for multiple frequency environments.
Measurement Quantification Factors
Most all standards are based on the far field relationships and their interaction with the body.
Near field exposures are difficult to measure and almost impossible to calculate (simply), because of mutual coupling effects.
SAR is impossible to practically measure.
57
The solution …
Measure the Electric Field (E) in V/m;
Measure the Magnetic Field (H) in A/m;
Measure the Power Density (S) in mW/cm2;
Then compare those field results to published “limit” values that,
under maximal absorption conditions, would result in an SAR of no
more than 0.4 W/kg for controlled environments, or 0.08 W/kg for
uncontrolled environments.
58
59 Let’s go to Kwajalein…
60 Perception is underrated
Calculation – vs. Measurement?
EVERYONE believes a measurement …
EXCEPT the person who made it.
NO ONE believes a calculation …
EXCEPT the person who did it.
61
… a matter of perception
Travel to Kwajalein is no easy task …
Typical Itinerary
Up at 4 am to get to airport by 6 am for a 8 am flight to points VERY WEST.
Arrive at Honolulu airport 12 hours later to Hawaiian hospitality.
Up at 4 am to get to lobby at 5 am to get to Hickam field by 6 am to muster at the gate at 7 am for an 8 am Military Air Command (MAC) flight to US Army Kwajalein Atoll (USAKA).
Arrive at USAKA 6 hours later to US Army hospitality.
62
Last leg from Kwajalein to Roi-Namur*
Typical Itinerary
Once cleared through USAKA; get onto “flight list” to take the last 50 mile flight up the lagoon to the Islands of Roi-Namur; the main site of Sensor and control.
Arrive at Roi and settle into to VIP accommodations.
63
* NO GUARANTEE YOU MAKE IT THERE WHEN YOU WANT TO
This isn’t Kansas … 64
Japanese HQ, Kwajalein Gun Emplacement Japanese Cemetery
Wasn’t all work … 65
Swimming Exploring
Unexploded Shells
9 Hole Golf Course 19th Hole
Preparation for RF Field measurements 66
RF Measurements
RF Safety measurements focus on trying to determine RF field levels under conditions that are anything but controlled.
Output levels vary over time.
Multiple emitters and modulation schemes.
Reflections from towers, buildings, and the ground.
Field interactions.
Influence of the surveyor and the instruments.
67
Spatial Averaging
Measurements are averaged over an area equivalent to the vertical cross section of the human body.
SAR limit based on average energy absorbed over the body.
The limbs can tolerate higher levels since the body’s circulatory system acts as a coolant with the remainder of the body functioning as a radiator (20:1).
Basic Limit apply for the eyes and testes due to poor blood flow of these organs.
68
Shape Orientation and Polarization
Human body in a vertical position absorbs 10 times more energy in a vertically polarized field than in a horizontally polarized field.
Similarly, a prone body in a horizontally polarized field also absorbs the most energy.
69
Time averaging Exposure
• Because the primary effect is thermal, exposure is averaged over time. • In most standards, the averaging time is six minutes (controlled), which
is close to the thermal regulatory response time of the human body. • There are also limits on the peak exposure levels:
Transmitted Power • Pulsed System: Duty cycle = (PW ∗ PRF) • Rotating Antennas: TD = (ΘAZ ∗ 60)/(360° ∗ n); in seconds
70
Σ Sexp ∗ texp = Slimit ∗ tavg
Where: Sexp = power density level of exposure (mW/cm2), Slimit = appropriate power density MPE limit (mW/cm2),
texp = allowable time of exposure for Sexp, and
tavg = appropriate MPE averaging time
Compliance in a Multi-Signal Environment 71
Figures courtesy of NARDA
Determination of Type of Probe/Meter
Frequency: If multi-frequency, use broadband true root mean square (rms).
Response Time (< 3s desirable).
< 1s for detecting intermittent fields.
Recording or averaging capabilities for fluctuating fields.
Peak limitations (> factor of 10).
Polarization (isotropic, maximum deviation < 1dB).
Non-linearity (< 20%).
Other:
Temperature sensitivity (< 1dB, 0 - 130°F) and zero drift (< 10% per hour).
Battery life (if DC, > 8 hours) and response due to supply voltage (< 20%).
Susceptibility to RFI (minimum).
Weight; durability; ease of use.
72
RF Measurements: Safety Precautions
Care should increase in proportion to power level.
Precautions are different for deliberate radiating system surveys than leakage surveys.
Use estimation calculations.
73
Formula for HP15C Field-work 74
RF Measurements: Indirect Hazards
High Voltage (HV): Shock hazards.
Prime RF-leakage source may be HV electrodes of transmitting
tubes.
X-Rays: Survey for x-rays first; beware of RF interference.
DC magnetic fields.
Indirect RF Hazards: Electroexplosive devices (EEDs), flammable
materials, pacemakers, prosthetic implants, computers.
Burns: RF, thermal (hot and cold).
Abnormal modes of operation.
75
RF Measurements: Radiating Hazards
MPE: may use lower PPk, then extrapolate to higher power levels; limit exposure, duration.
Moving antennas.
Theoretical RF patterns.
Metallic structures and reflectors.
76
RF Measurements: Leakage Surveys Waveguides and coax
Set scales at MPE.
Beware of leakage ports.
Interlocks
Do not defeat interlocks on doors/panels.
Check operation by surveying with port closed, then open.
Foreign objects.
Inspect flexible waveguides.
77
Flexible Waveguide Failure 78
RF Measurements: Procedures Far-Field, Single Source
Scanning: Scan area of interest along axis of propagation.
Fixed Point (> 20cm from object):
Survey along > 8-10 evenly distributed points per wavelength.
Average over maxima and minima. Spatial average over the plane occupied by the body.
Account for reflections from support structures:
Perform either scanning or fixed multiple point surveys over several wavelengths along the axis of propagation.
Vary the distance from probe to support structure, while keeping the distance from the source to probe constant.
79
RF Measurements: Procedures
Complex Far-Field Sources
Use broadband isotropic probe.
Account for reflections by performing a scanning survey.
Beware of cable reflections and pick-up.
80
RF Measurements: Procedures
Near Field Conditions/Non-Uniform Fields
Normally use isotropic probe.
Perform a series of continuous scans.
Map the fields over the area of interest.
Make use of spacers
81
RF Measurements: Unique Problems
Extremely Low Frequency (ELF) and Very Low Frequency (VLF) Interference: Perform survey with instrument and probe in the same hand.
Cover probe with Sn/Cu/Al-foil or Narda “sock” to check for ELF/VLF.
Perform ELF, VLF survey.
Environmental Considerations: Outdoors: temperature, humidity, precipitation.
Indoors: cleanrooms, radioisotope laboratories, security clearance restricted areas, surgery rooms.
Height: towers, rooftops.
Traffic: sidewalks, highways.
82
RF Measurements: What to Measure?
IEEE Std C95.1™-1991 COMPLIANCE
f = 100 kHz to 110 MHz: RMS induced and contact current
limits for continuous sinusoidal waveforms.
f = 0.1 – 100 MHz: Both magnetic and electric field strengths
must be obtained.
f = 100 – 300 MHz: Both magnetic and electric field strengths
should be ascertained, but may be able to quantify the fields
with only the E field.
f = 300 MHz – 300 GHz: Plane wave power density.
83
RF Measurements: Units? 84
Electric, magnetic, EM, & dosimetric quantities and corresponding SI units
Quantity Symbol Unit
Conductivity F siemens per meter (S/m)
Current I ampere (A)
Current density J ampere per square meter (A/m2)
Frequency f hertz (Hz)
Electric field strength E volt per meter (V/m)
Magnetic field strength H ampere per meter (A/m)
Magnetic flux density B tesla (T)
Magnetic permeability µ henry per meter (H/m
Permittivity ε farad per meter (F/m)
Power density S watt per square meter (W/m2)
Specific energy absorption SA joule per kilogram (J/kg)
Specific energy absorption rate SAR watt per kilogram (W/kg)
RF Measurements: GAME PLAN ALTAIR 85
UHF and VHF combined and separate. E field evaluation each location with Narda 8718 meter
with 8722 E field probe. H field evaluation each site for (VHF) with Narda 8731
and 8754 H field probes.
Verify main lobe, side lobes, and back lobes.
Confirm predictive levels.
“Spot check” residence dwellings and airport.
RF Measurement Locations: ALTAIR 86
RF Measurement Locations: ALTAIR 87
RF Measurement Locations: MMW/TRADEX/ALCOR 88
RF Measurements: RESULTS 89
Survey Measurement: ALTAIR VHF & UHF Combined @ 2°
Distance from Sensor Raw Meter Reading (%MPE(Occ))
Extrapolated to Full Power
Predicted Maximum (%MPE(Occ))
600' 13.14% 26.75% 36.59%
550' 23.61% 48.06% 65.75%
500' 25.80% 52.51% 71.85%
450' 47.10% 95.87% 131.17%
400' 53.70% 109.30% 149.55%
350' 45.60% 92.82% 126.99%
300' 37.50% 76.33% 104.43%
250' 48.60% 98.92% 135.34%
200' 83.40% 169.76% 232.26%
150' 70.50% 143.50% 196.33%
100' 46.80% 95.26% 130.33%
RF Measurements: RESULTS 90
Survey Measurement: ALTAIR VHF & UHF Combined @ 3°
Distance from Sensor Raw Meter Reading (%MPE(Occ))
Extrapolated to Full Power
Predicted Maximum (%MPE(Occ))
600' 13.05% 25.56% 36.34%
550' 15.15% 30.84% 42.19%
500' 11.94% 24.30% 33.25%
450' 45.30% 88.54% 121.14%
400' 38.70% 78.88% 107.77%
350' 27.90% 56.79% 77.70%
300' 57.00% 116.02% 158.74%
250' 45.60% 92.82% 126.99%
200' 60.90% 123.96% 169.60%
150' 26.70% 54.35% 74.36%
RF Measurements: RESULTS 91
Survey Measurement: ALTAIR VHF & UHF Combined @ 5°
Distance from Sensor Raw Meter Reading (%MPE(Occ))
Extrapolated to Full Power
Predicted Maximum (%MPE(Occ))
600' 11.61% 23.63% 32.33%
550' 9.29% 18.81% 25.73%
500' 15.87% 32.30% 44.20%
450' 20.91% 42.56% 58.23%
400' 23.25% 47.32% 64.75%
350' 18.90% 38.47% 52.63%
300' 38.10% 77.55% 106.10%
250' 53.70% 109.30% 149.55%
200' 36.00% 73.28% 100.25%
150' 46.50% 94.56% 129.50%
100' 69.30% 141.06% 192.99%
Conclusions of Initial RF Field Measurements
There are accessible areas where an uninformed person could receive an exposure to RF energy in excess of human limits.
Although OSHA did not require RF Safety Programs (at the time), USAKA did have some safety rules regarding RF safety.
There is need for a comprehensive RF Safety Program specific to the Kwajalein Atoll complex.
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93 Safety programs must effectively communicate RISK
RF “CAUTION” sign on Roi-Namur (circa 1990) “CAUTION” sign on Mt. Wilson warning of climbing over cliffs (courtesy Ric Tell), NOT RF
from nearby towers.
“All of us is smarter than any of us”
Ric Tell (Richard Tell Associates) hired as consultant on the project.
94
Basics of an RF Safety Program
RF hazard identification and periodic surveillance by a competent person.
Identification and Control of RF Hazard Areas.
95
Essentials of an RF Safety Program
Implementation of controls and SOP’s to reduce RF exposures to levels in compliance with applicable guidelines.
RF safety and health training to ensure that all employees understand the RF hazards and control methods used.
Employee involvement in the structure and operation of the S&H Program.
96
Essentials of an RF Safety Program (cont.)
Implementation of an appropriate medical surveillance program (Implanted Medical Devices (IMDs).
Periodic (e.g., annual) reviews of the program to identify and resolve deficiencies.
Assignment of responsibilities, including adequate authority and resources to implement and enforce the program.
97
Extent of RF Safety Program
Locations were categorized based on potential RF exposures.
Many RF exposure situations required no, or a limited RF Safety Program (Lower tier categories).
More extensive program elements for higher exposure potential (Higher tier categories).
98
Based on Potential for RF Exposure
Core Program Elements
Administrative
Identification of Potential Hazards
Controls
Engineering
Administrative
Personal Protective Equipment (PPE)
Training
Program Review
99
Core Program Elements: Administrative
Policy
• Management Commitment
• Authority to enforce rules
Accountable Persons
• Assignment of Duties
Documentation
Employee Involvement
RF Safety Committee
Procurement of RF Source Equipment
100
Core Program Elements: Identification of Potential Hazards
Inventory of RF Sources.
RF Exposure Assessment:
Establish exposure categories.
Ensure controls are functioning.
101
Category of Areas
102
Category Number Potential RF Exposure Condition Controls Required
1 Lower (Public) Tier not Exceeded None
2 Lower (Public) Tier may be exceeded
but Upper (Worker) Tier not Exceeded
Signs, training
3 Upper (Worker) Tier may be exceed
unless controls implemented
Signs, specific training
4 > 10 X the Upper (Worker) Tier Signs, barriers
Core Program Elements: Controls
Engineering
Utilize equipment & site configuration to control hazard areas.
Access Restriction.
Maintenance of Controls.
103
Administrative
RF “Warning” Signs; what to post and where.
Access Restriction; with and without training
Work Practices.
Control of Power Source (LOTO).
Area Monitors.
Incident Response.
Medical Surveillance (e.g. IMDs).
Maintenance of Controls.
104 Core Program Elements: Controls
Personal Protective Equipment (PPE)
A PPE Program must ensure its effectiveness, including the proper selection of RF PPE within tested capabilities, and accessibility, use, & maintenance.
105
From Ric Tell
Core Program Elements: Controls
Core Program Elements: Training
What to teach?
Location of sources and potentially hazardous areas.
Health effects and safety standards.
Extent of exposures compared to standards and common sources.
Required SOP’s and controls.
Emergency procedures.
How to know when things are “abnormal”.
Optional controls employees may use.
106
Core Program Elements: Program Review
Adequacy of Program Design.
Program Implementation.
Interview employees.
What are the hazards and controls?
What steps have been taken to enforce the rules?
Determine what to change, add, and delete.
107
This was the “birth” of IEEE Std C95.7
IEEE Recommended Practice for Radio Frequency Safety Programs, 3 kHz to 300 GHz: IEEE Std C95.7™-2014.
IEEE Standards Coordinating Committee 39, sponsored by the IEEE International Committee on Electromagnetic Safety (ICES).
108
THANK YOU … Questions?
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