United States
Environmental Protection
Agency
Office of Radiation Programs
Las Vegas facility
P.O. Box 15027
Las Vegas NV89114
ORP/EAD-78-3
August 1978
Radiation
•SEPA
Measurements of
Radiofrequency Field
Intensity in Buildings
with Close Proximity
to Broadcast Stations
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MEASUREMENTS OF RADIOFREQUENCY FIELD INTENSITY IN BUILDINGS
WITH CLOSE PROXIMITY TO BROADCAST STATIONS
Richard A. Tell
Norbert N. Hankin
August 1978
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
Electromagnetic Radiation Analysis Branch
P.O. Box 15027
Las Vegas, Nevada 89114
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DISCLAIMER
This report has been reviewed by the U.S. Environmental Protection Agency's
Office of Radiation Programs Las Vegas Facility and Silver Spring, Maryland
Facility, and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendations for their use.
ii
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PREFACE
The Office of Radiation Programs of the U.S. Environmental Protection
Agency carries out a national program designed to evaluate population
exposure to ionizing and nonionizing radiation, and to promote development
of controls necessary to protect the public health and safety. This
report describes a series of measurements of radiofrequency field inten-
sities performed in several tall buildings that are located adjacent to
high power broadcast facilities to access exposure of individuals living
or vrorking in these situations. Readers of this report are encouraged
to inform the Office of Radiation Programs of any omissions or errors.
Comments or requests for further information are also invited.
Floyd L. Galpin, Director
Environmental Analysis Division
Office of Radiation Programs
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ABSTRACT
This report summarizes the results of a series of radiofrequency field
intensity measurements made in eight tall buildings located in New York,
Miami, Chicago, San Diego, and Houston. The buildings, in which the measure-
ments were made, were selected because of their proximity to FM radio and/or
VHP and UHF television transmitting antennas. These broadcast antennas were
usually located on nearby buildings so that the possibility existed for high
intensity illumination of the upper floors of the buildings selected by the
main beam of radiation of the antennas. The principal objective in conducting
these measurements was to obtain information about the field intensities which
can be produced by broadcast antennas at locations close to the antennas and
near the main beam axis. In addition, the measurements help in determining
the higher level radiofrequency exposures of persons who work and live in tall
buildings under similar irradiation situations, and in developing techniques
which allow estimates to be made of exposures under such conditions.
The maximum power densities derived from electric field intensity measure-
ments in any of the eight buildings were less than 100 microwatts per square
centimeter (yW/cm2). Higher exposures were observed at unobstructed locations
on roofs of some of the buildings. Observations about factors which were
found to affect exposure levels are discussed.
iv
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TABLE OF CONTENTS
Page
Abstract 1 v
Li st of Tabl es vl
Li st of Fi gures vi i
Introduction 1
Bui 1 ding Measurement Results 3
Measurement Technique 5
Building Measurements 8
New York 8
Mi ami 18
Chicago 20
San Di ego 26
Houston 29
Concl usions 33
References 35
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LIST OF TABLES
Number Page
1 Building Measurement Summary 2
2 Summary - Power Densities for All Building
Measurements 4
3 New York FM Radio Stations Contributing to Measured
Levels 9
4 New York TV Stations Contributing to Measured
Level s 10
5 Empire State Building - Measured Electric Field
Intensities 11
6 World Trade Center - Measured Electric Field
Intensities from FM Radio 12
7 World Trade Center - Measured Electric Field
Intensities from Television 13
8 Pan Am Building - Measured Electric Field
Intensities, 54th Floor 14
9 One Biscayne Tower - Measurements of Electric Field
Intensities from WTMI-FM 19
10 Sears Tower - Measured Electric Field Intensities
from FM Radio; 50th Floor Office 22
11 Sears Tower - Measured Electric Field Intensities
from FM Radio; Roof 23
12 Sears Tower - Measured Electric Field Intensities
from Television 24
13 Federal Building (39th Floor Office) - Measured
Electric Field Intensities - TV and FM 25
14 Home Tower - Measurements of Electric Field
Intensities from KITT-FM 28
15 Mi lam Building - Measured Electric Field Intensities,
47th Floor 30
VI
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LIST OF FIGURES
Number Page
1 Singer Dipole Calibration Data 5
2 Near Field Gain Compression for a 12 Bay Dipole
Array 31
vii
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INTRODUCTION
This report describes the results of a series of measurements of radio-
frequency (RF) field intensities made in eight different tall buildings
located in five large United States cities. The measurements were made for
the purposes of (1) determining the RF field intensities close to broadcast
antennas near the main beam axis so that analytical techniques may be developed
to allow estimates of field intensities for such exposure situations, and (2)
determining the higher level general population RF exposure which can exist
for persons who live or work in tall buildings situated close to high power FM
radio and television transmitting installations. These buildings, due to
their height and locations, have the upper parts of their structure illuminated
by the main beam of radiation from the transmitting antennas.
In each instance the measurements were conducted in conjunction with a
general, ground level RF survey of the given metropolitan area. The cities,
buildings in which measurements were made, locations of the major broadcast
transmitters, and the date of the measurements are summarized in Table 1. In
all but two of the eight buildings involved in these measurements there was a
high power broadcast antenna in the immediate vicinity. In measurements at
the Empire State Building, the exposure levels measured were due to antennas
mounted on the building itself. In measurements at the other buildings, the
exposures measured were primarily due to radiation from antennas mounted on
buildings other than the ones involved in the measurements.
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TABLE 1. BUILDING MEASUREMENT SUMMARY
City
Building in Which
Measurements were Made
Location of Primary
Transmitters
Transmitters
Date of Measurement
ro
Miami
New York
Chicago
San Diego
Houston
One Biscayne Tower
Empire State Building
Pan Am Building
World Trade Center
South Tower
Sears Tower
Home Tower
Mi lam Building
100 Biscayne Boulevard
Empire State Building
(1) Chicago Board of
Trade
(2) 105 W. Adams
Bank of America Bldg.
(1) Tenneco Building
(2) One Shell Plaza
WTMI-FM
Many
WCIU-TV(26)
WBEZ-FM
KITT-FM
KLEF-FM
KVRL-TV(26)
February 1976
August 1976
September 1976
May 1977
September 1977
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Building Measurement Results
The results of the measurements for all of the buildings listed in Table
1 are summarized in terms of far field equivalent power density. The results,
presented in Table 2, are the power densities, derived from the measurements
of electric field intensities, existing at each measurement location. Power
densities due to FM radio and television broadcast bands are shown individually
in addition to the total combined power density for these bands.
The measurement data taken provided much more detail than appears in the
summary presented in Table 2. In most of the measurements, the electric field
intensities and power densities were obtained for each contributing FM radio
or television station. In the case of FM radio transmission, many of the
measurements specified the electric field intensities and power density
associated with radiation transmission for both the horizontal and vertical
polarization planes. The descriptions of building measurements for each city
and location, and a much more detailed presentation of measurement results are
presented in the following sections of this report.
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TABLE 2. SUMMARY - POWER DENSITIES FOR ALL BUILDING MEASUREMENTS
City
Measurement Location Power Density (yW/cm2)
FM Radio Television
Total Power Density
(yW/cm2)
New York
Mi ami
Chicago
San Diego
Houston
Empire State Building
86th floor observatory 15.2
(outside)
102nd floor observatory
(inside)
Near Window 30.7
Near Elevator 1.35
World Trade Center
South Tower
107th floor observatory 0.10
Roof 0.15
Pan Am Building
54th floor 3.76
One Biscayne Tower
26th floor 6.69
30th floor 5.24
34th floor 62.1
38th floor 96.8
Roof - partially shielded
area 134
Roof - open area 148
Sears Building
50th floor - near window 31.7
Roof 201
Federal Building
39th floor 5.74
Home Tower
10th floor 18
17th floor 0.22
Roof location 1 180.3,126*
Roof location 2 119.0,162*
1100 Milam Building
47th floor 35.8
1.79
1.10
7.18
6.52
34.2
29.0
.730
31.6
15.2
32.5
1.35
1.20
7.33
10.3
6.69
5.24
62.1
96.8
134
148
65.9
230
6.47
18
0.22
180.3
119.0
67.4
*Measured with the NBS probe EDM-3.
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Measurement Technique
The measurements of electric field intensity in buildings were performed
with an instrumentation system consisting of a tuned half-wave dipole receiving
antenna connected through coaxial attenuators to a scanning spectrum analyzer.
Signal amplitudes, representing power received by the antenna, were measured
with the spectrum analyzer and corrected for signal attenuation and antenna
calibration factors to obtain incident electric field intensity. The set of
Singer tunable dipole antennas used in the measurements had been previously
calibrated by referencing them to a set of National Bureau of Standards
calibrated dipoles. A detailed description of this calibration process is
available elsewhere (Tell, et al., 1976). Figure 1 provides the dipole
antenna factor as a function of frequency for the Singer dipoles used. The
maximum deviation of the fitted calibration curve from measured data is
1.3dB. The spectrum analyzer was a Tektronix model 7L13.
40 r-
30
CD
2
u
<
u.
<
z
111
20
10
O MEASURED DATA
SOLID LINE IS LEAST SQUARES FIT
MAXIMUM DEVIATION FROM MEASURED DATA
IS 1.3dB
WITH 20* RG-55 CABLE
30
50
70 100 200
FREQUENCY(MHZ)
'
300
' ' '
TOO
Figure 1. Singer dipole calibration data
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The data processing procedure consisted of: (1) correcting the measured
power (in dBm), as indicated by the spectrum analyzer, for any external
attenuation which may have been used for instrument protection; (2) conversion
of the power reading (in dBm) to a voltage produced in the 50ft system (dByV),
and (3) adding the appropriate antenna factor to determine the electric field
intensity incident on the antenna. In effect, the electric field strength is
defined by:
E(dByV/m) = P(dBm) + 107 + A (dB)
where:
E = electric field intensity in dByV/m
P = power detected from antenna in dBm
107 = conversion factor for converting from dBm to dByV
in a 50ft system
A = antenna factor in dB
The electric field intensity is then expressed in units of volts/meter
and converted to equivalent free space power density S(yW/cm2) through the
relations:
E(V/m) = 10 Exp[E(dByV/m)/20-6]
S(yW/cm2) = 100 x CE(V/m)]2
377ft
where:
377ft is the impedance of free space
In addition to measurements made with the spectrum analyzer and tuned
dipoles, measurements were made in San Diego and Houston using the National
6
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Bureau of Standards hazard survey probe EDM-3. The EDM-3 measures the electric
field energy density, U£. Electric field energy density is a meaningful
measure of the RF intensity in the near field of an antenna and is superior to
the parameter power density, the values of which can be erroneous when applied
to the near field. The measured electric field energy density, UE, can 'be
related to the far field power density, S, by the relation
S(yW/cm2)=60UE(nJ/m3)
where electric field energy density, IL, is expressed in units of nanojoules
per cubic meter (nJ/m3). Alternatively, the square of the electric field
strength, E, expressed in units of volts squared per meter squared (V2/m2) is
related to the electric field energy density by the relation
E2(v/m)2 = 2xlQ-9UE(nJ/m3)
where e is the permitivity of free space and is equal to 8. 854x1 O"12 farads/
meter (F/m). The units of V2/m2 are used as another method of quantifying the
exposure in the near field as provided for in the American National Standards
Institute (ANSI) standard C95.1 - 1974. This unit is related directly to the
measured electric field energy density without assumptions about the relationship
between the electric and magnetic field components. A technical description of
the EDM-3 has been given by Tell and O'Brien (1977), in relation to work in
the vicinity of FM and TV transmitters, and by Bowman (1974).
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BUILDING MEASUREMENTS
New York
Measurements of electric field intensity were made at the Empire State
Building inside the 102nd floor observatory and outside on the 86th floor
observatory, at the World Trade Center - South Tower inside the 107th floor
observatory and on the roof, and at the Pan Am Building in a 54th floor
office. Virtually all FM radio and television (TV) stations in New York City
presently transmit from the top of the Empire State Building. Measurement
locations were chosen at the World Trade Tower and the Pan Am Building that
allowed direct line of sight paths to the Empire State Building. Tables 3 and
4 list the FM radio and TV stations whose signals were monitored during these
measurements. Fifteen FM radio and seven TV stations transmit from the Empire
State Building.
The 102nd floor observatory of the Empire State Building is a unique
location in that, besides being a popular tourist attraction, a unique double-
ring array of FM dipole elements, diplexed to 11 FM stations simultaneously,
is affixed to the exterior of the building with the upper ring of dipoles
being approximately four feet from the glass windows of the observatory. The
observatory windows are coated with a special electrically conductive film for
the purpose of significantly attenuating the radiofrequency fields which
propagate into the observatory area. This attenuation was apparent in that
the measured electric field intensities inside the observatory were much lower
than would be expected if there were no attenuating film on the windows.
The results of the measurements at the five building locations are
presented in Tables 5-8. The electric field intensity and power density
contribution for each FM radio and TV station are presented in addition to
8
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TABLE 3. NEW YORK FM RADIO STATIONS CONTRIBUTING TO MEASURED LEVELS
Station Frequency (MHz) EPR (kW)1 HAAT2 (Ft)
Horizontal Plane Vertical Plane
*WKTU-FM
WPAT-FM
*WNYC-FM
*WPLJ-FM
*WQXR-FM
*WNWS-FM
*WEVD-FM
*WXLO-FM
*WBAI-FM
*WCBS-FM
*WPIX-FM
*WNEW-FM
*WNCN-FM
*WRFM-FM
*WRVR-FM
*WBLS-FM
92.3
93.1
93.9
95.5
96.3
97.1
97.9
98.7
99.5
101.1
101.9
102.7
104.3
105.1
106.7
107.5
5.4
12.5
5.3
4.6
5.4
3.6
5.3
5.4
5.4
4.6
5.4
4.1
5.4
5.4
5.4
2.0
3.8
12.5
3.8
3.8
3.8
3.8
3.85
3.8
3.8
3.7
3.8
1.45
1220
870
1220
1300
1220
1450
1220
1220
1220
1330
1220
1360
1220
1220
1220
1220
*Indicates stations transmitting from Empire State Building.
Effective radiated power (kilowatts) in horizontal and vertical
polarization planes; single entry indicates horizontal polarization only.
2Height above average terrain.
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TABLE 4. NEW YORK TV STATIONS1 CONTRIBUTING TO MEASURED LEVELS
Station Channel ERP (kW) HAAT (Ft)
Visual Carrier Aural Carrier
WCBS
WNBC
WNEW
WABC
NOR
WPIX
WNET
2
4
5
7
9
11
13
42.0
30.2
37.1
110
155
100
25.3
8.32
5.13
5.5
11
31.
19.5
5.36
1300
1440
1330
1465
1240
1410
1200
stations are located on the Empire State Building.
10
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TABLE 5. EMPIRE STATE BUILDING-MEASURED ELECTRIC FIELD INTENSITIES
Station
86th Floor Observatory
E(V/m) S(yW/cm2)
WKTU-FM
WPAT-FM
WNYC-FM
WPLJ-FM
WQXR-FM
WNWS-FM
WEVD-FM
WXLO-FM
WBAI-FM
WCBS-FM
WPIX-FM
WNEW-FM
WNCN-FM
WRFM-FM
WRVR-FM
WBLS-FM
WOR-TV(9)
Visual
Audio
WNET-TV(IS)
Visual
Audio
Total Power
FM
TV
2.25
0.12
2.13
0.30
2.25
0.19
2.13
2.53
2.68
0.43
2.53
0.95
2.39
2.39
1.90
1.34
-
_
-
-
Density (yW/cm2)
102nd Floor Observatory
Near Window Center of Room
E(V/m) S(yW/cm2) E(V/m) S(uW/cm2)
1.35
0.0038
1.20
0.024
1.35
0.0095
1.20
1.70
1.90
0.048
1.70
0.24
1.51
1.51
0.95
0.48
.,
-
—
-
3.78
-
4.01
-
4.01
-
3.37
3.78
3.78
-
3.01
-
2.39
2.39
2.53
1.60
1.97
0.70
1.26
0.89
3.80
-
4.26
-
4.26
-
3.02
3.80
3.80
-
2.40
-
1.51
1.51
1.70
0.68
1.03
0.13
0.42
0.21
0.95
-
0.75
-
0.30
-
0.80
0.95
0.95
-
0.75
_
0.45
0.43
0.30
0.15
_
-
—
-
0.24
-
0.15
-
0.024
-
0.17
0.24
0.24
_
0.15
-
0.054
0.048
0.024
0.006
—
-
—
-
15.2
30.7
1.79
1.35
11
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TABLE 6. WORLD TRADE CENTER
MEASURED ELECTRIC FIELD INTENSITIES FROM FM RADIO
Station 107th Floor Observatory Roof Observatory
E(V/M) S(yW/cm2) E(V/m) S(yW/cm2)
Horizontal Vertical Horizontal Vertical
WKTU-FM 0.16 0.06 .0077 0.10 0.17 .010
WPAT-FM 0.10 0.08 .0042 0.15 0.27 .025
WNYC-FM 0.13 0.05 .0056 0.10 0.10 .0051
WPLJ-FM 0.12 0.06 .0048 0.13 0.13 .0096
WQXR-FM 0.17 0.07 .0090 0.14 0.15 .011
WNWS-FM 0.13 0.04 .0052 0.12 0.01 .0038
WEVD-FM 0.27 0.11 .022 0.15 0.12 .0098
WXLO-FM 0.24 0.08 .017 0.16 0.13 .012
WBAI-FM 0.17 0.08 .0095 0.13 0.11 .0077
WCBS-FM 0.27 0.04 .019 0.08 0.15 .0079
WPIX-FM 0.08 0.05 .0021 0.17 0.15 .014
WNEW-FM 0.04 0.08 .0018 0.16 0.13 .012
WNCN-FM 0.05 0.05 .0014 0.12 0.11 .0068
WRFM-FM 0.07 0.04 .0016 0.13 0.13 .0096
WRVR-FM 0.05 0.04 .0011 0.13 0.11 .0078
WBLS-FM 0.02 0.03 .00032 0.07 0.05 .0020
Total S(yW/cm2) .11 .15
12
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TABLE 7. WORLD TRADE CENTER
MEASURED ELECTRIC FIELD INTENSITIES FROM TELEVISION
Station
WCBS (2)
Visual Carrier
Aural Carrier
WNBC (4)
Visual Carrier
Aural Carrier
WNEW(5)
Visual Carrier
Aural Carrier
WABC (7)
Visual Carrier
Aural Carrier
WOR (9)
Visual Carrier
Aural Carrier
WPIX (11)
Visual Carrier
Aural Carrier
WNET (13)
Visual Carrier
Aural Carrier
Total S(yW/cm2)
*Not measured
107th Floor Observatory
E(V/m) S(yW/cm2)
Roof Observatory
E(V/m) S(uW/cm2)
0.06
0.35
0.72
0.10
0.78
0.22
0.93
0.37
0.78
0.49
0.94
0.30
.00095
.032
.14
.0026
.16
.013
.23
.036
,16
,065
.23
.023
0.22
0.10
0.19
0.09
0.66
0.35
2.94
0.70
2.21
1.80
1.67
0.84
2.24
0.80
1.09
0.013
0.0026
0.0096
0.0019
0.11
0.032
2.30
0.13
1.29
0.86
0.74
0.19
1.33
0.17
7.18
13
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TABLE 8. PAN AM BUILDING
MEASURED ELECTRIC FIELD INTENSITIES, 54TH FLOOR
FM Radio
Station E(V/m) S(yW/cm2)
Horizontal Vertical
Television
Station E(V/m) S(yW/cm2)
WKTU-FM
WPAT-FM
WNYC-FM
WPLJ-FM
WQXR-FM
WNWS-FM
WEVD-FM
WXLO-FM
WBAI-FM
WCBS-FM
WPIX-FM
WNEW-FM
WNCN-FM
WRFM-FM
WRVR-FM
WBLS-FM
1.07
0.30
0.75
0.60
1.13
0.38
1.13
1.34
1.20
0.36
1.20
0.60
0.75
0.75
0.85
0.48
0.60
0.34
0.42
0.24
0.42
0.03
0.48
0.60
0.48
0.15
0.38
0.38
0.19
0.17
0.05
0.05
0.40
0.054
0.20
0.11
0.38
0.038
0.40
0.57
0.44
0.040
0.42
0.13
0.16
0.16
0.19
0.061
WCBS (2)
Visual
Aural
WNBC (4)
Visual
Aural
WNEW (5)
Visual
Aural
WABC (7)
Visual
Aural
WOR (9)
Visual
Aural
WPIX (11)
Visual
Aural
WNET (13)
Visual
Aural
1.10
0.78
0.68
0.30
1.75
0.87
0.93
0.42
3.12
1.56
1.33
0.21
1.78
0.50
0.32
0.16
0.12
0.024
0.81
0.20
0.23
0.046
2.57
0.65.
0.47
0.012
0.84
0.067
Total S
3.76
6.52
14
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the total power density determined at each measurement location. Measurements
in the FM band were made with the dipole antenna adjusted for the frequency at
the center of the FM band, i.e., 98 MHz. The individual signals produced by
each FM station could be viewed on the spectrum analyzer CRT in the scan of
the FM band. Measurements in the Empire State Building were performed with
the antenna oriented to obtain generally maximized signals for the entire
group of FM stations. Separate measurements (in the FM band) were made of the
horizontal and vertical components of electric field intensity at the World
Trade Center and the Pan Am Building. A single azimuthal orientation of the
dipole antenna in the horizontal plane was sufficient to yield a maximum
response for the horizontal plane component.
Several observations from these results are pertinent. The maximum
exposure level was found in the 102nd floor observatory of the Empire State
Building and was 32.5 yW/cm2 for the stations measured; almost all of this is
due to the adjacent FM transmitting antenna array mounted near the windows.
Exposure from all FM and VHF-TV stations in the 107th floor observatory of the
World Trade Center was 1.2 yW/cm2, and on the roof of the World Trade Center
the corresponding exposure was 7.3 yW/cm2; in both cases the TV signals
accounted for the principal part of the total exposure. Total exposure from
all FM and VHF-TV stations in the 54th floor office in the Pan Am Building was
10.3 yW/cm2, with the contribution from television transmission being greater.
The effect of antenna radiation pattern on exposure situations can be
seen from the measurements made at the buildings in New York. The 86th floor
measurements at the Empire State Building were made below the FM dipole array
and the television antennas, and outside of the building where walls, ceilings,
and roofs would not act to attenuate the radiation levels. Measurements made
at the World Trade Center and Pan Am Building were made in the main beam of
the television antennas located on the Empire State Building; the measurement
locations at the World Trade Center being close to the maximum intensity of
the main beam. A comparison of the TV measurements shows very little power
transmitted in a downward direction as compared, to power transmission in the
forward direction. Electric field intensity due to TV transmission (in the
downward direction) at the 86th floor of the Empire State Building was negligible,
while at the Pan Am Building and the World Trade Center the electric field
15
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intensity, due to TV transmission in the horizontal direction, levels were
much greater even though these buildings are much more distant from the
sources.
Although the total power transmitted in the FM radio band by the Empire
State Building antennas is much less than that for television transmission,
the field intensity (and power density) measured on the 86th floor observatory
is significant and much greater than that due to TV transmission. This shows
that significantly more power is radiated in the downward direction from the
FM antennas than for the TV antennas, i.e., the TV antenna radiation patterns
are more directional than those of the FM antennas. Power densities due to
the FM transmission at the World Trade Center and Pan Am Building, also due to
main beam exposure are less than those due to TV transmission because of the
lower power of the FM stations. All of the summarized results of the building
measurements in New York are included in Table 2.
The electric field intensities (and associated power densities)
measured in the Empire State Building's 102nd floor observatory would be
much greater if the observatory windows were not coated with the electrically
conductive film used to attenuate the electric fields produced by the FM
antenna array just outside of the observatory. The attenuating effects
of the film on the intensity of the electric field associated with FM
radio transmission can be estimated by comparing typical measured field
intensities to that which would be expected to exist if the film was not
present. The possible range of attenuation is estimated by using in the
comparisons two FM stations (using the dipole array.) of equal effective
radiated power near the extremes of the FM radio band.
This appears to be a reasonable approach suggested by the measured
electric field intensities shown in Table 5. Of the eleven FM stations
which are diplexed to the dipole array, ten have total effective radiated
power (ERP) of approximately 9.2 kW (Table 2). Generally, the measured
16
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electric field intensities decrease as the radiation frequency increases,
indicating a possible variation in attenuation of the coated window as a
function of frequency. Therefore, WNYC-FM, at 93.9 MHz and producing a
measured field intensity of 4.01 V/m, and WRFM-FM, at a frequency of 105.1 MHz
and having a measured field intensity of 2.39 V/m, are taken to represent the
extremes in measured field strength and frequency.
The diplexed dipole array consists of 2 rings of 16 dipoles each, placed
at locations equidistant from one another around the circumference of the
observatory. Each dipole element transmits radiation for all FM stations, and
each transmits equal amounts of power; i.e., each of the ten FM stations of
9.2 kW ERP can be considered to radiate 1/32 of that from each dipole element.
Thus each element is considered to transmit with an ERP of 288 watts for each
of the ten FM stations involved. The distance between the nearest transmitting
dipole element and the measurement antenna is assumed to be 3 meters. At this
distance, the electric field strength produced by a half wave dipole transmitting
with an ERP of 1 watt is calculated to be 2 V/m. .Consequently, for the dipole
with an ERP equal to 288 watts, a field of 33.9 V/m would be produced at 3
meters if there was no attenuation. The ratio between the measured field
intensity of 4.01 V/m and the theoretical field intensity of 33.9 V/m is
0.118, or -18.5 dB. A comparison of the measured and calculated unattenuated
field intensity at the upper end of the frequency band yields a reduction
factor of -23.0 dB.
17
-------
Miami
Measurements of radiofrequency electric field intensities due to the
operation of an FM radio station, were made at several locations in a 40 story
Miami office building, One Biscayne Tower. The building is located very close
to the transmitting antenna of WTMI-FM, 93.1 MHz and 120 kW, which is atop a
nearby 30 story building at 100 Biscayne Boulevard. The roof of One Biscayne
Tower is higher than the WTMI antenna. The upper floors of the building are
exposed to main beam radiation.
Measurements were made at locations on the north side of the building,
where a direct view of the WTMI antenna exists from several floors. This
situation permits field intensity determinations, at several different locations,
to generally describe the vertical radiation pattern of the transmitting
antenna. Field intensity measurements were made on the 26th, 30th, 34th, and
38th floors, and the roof. Measurements were confined to vacated areas, not
yet occupied at the time. Venetian blinds were raised to assess maximum
possible exposure levels. Typical levels if the blinds were lowered and
closed would be expected to be significantly lower than those measured.
Measurements were made in both the horizontal and vertical polarization
planes, and the corresponding far field equivalent power densities determined.
The results of the measurements are tabulated in Table 9.
The maximum power density determined from measurements inside of the
building was 96.8 yW/cm2 on the 38th floor. Measurements were made of the
intensity of the WTMI-FM signal alone since, at the time of measurement, this
signal was by far the strongest of all being received in the building. The
contribution of other signals present was not determined, but would be expected
to increase the levels measured only slightly.
18
-------
TABLE 9. ONE BISCAYNE TOWER
MEASUREMENTS OF ELECTRIC FIELD INTENSITIES FROM WTMI-FM*
Measurement Location E(dByV/m) E*n*;,i (v/m) S(yW/cm2)
Horizontal Vertical
26th floor
30th floor
34th floor
38th floor
Roof - partially shielded
area
Roof - open area
*WTMI transmits at a frequency of 93.1 MHz and with an ERP of 120 kW.
124.5
127.5
137.5
141.5
143.5
140.5
133.5
131.5
142.5
143.5
144.5
146.5
5.02
4.44
15.3
19.1
22.49
23.64
6.68
5.24
62.1
96.8
134.1
148.2
19
-------
Chicago
Radio-frequency field intensities were measured inside a 50th floor
office and on the roof of the Sears Tower, and inside a 39th floor office of
the Federal Building. These two buildings were selected because of their
proximity to two nearby broadcasting stations, WBEZ-FM which transmits at 91.5
MHz with an ERP of 39 kW, and WCIU which transmits at 542 to 548 MHz with an
ERP of 1155 kW. The Sears Tower 50th floor office faced both WCIU-TV (Channel
26) and WBEZ-FM, and appeared to be approximately at the height of the centers
of radiation for both antennas. The 39th floor office of the Federal Building
is nearest to WBEZ-FM, but below the main beam of radiation.
Table 10 summarizes the FM band field intensity data and the total far-
field equivalent power density at the Sears Tower 50th floor office. The
total power density measured due to FM radio was 31.7 yW/cm2 with WBEZ contributing
31.3 yW/cm2. The stations are not identified by call letters or frequency in
Table 10. Measurements of FM fields at one location on the roof of the Sears
Tower, presented in Table 11, show that four FM stations are the major contributors
to a total power density due to FM radio transmission, of 200.8 yW/cm2. Four
FM stations have their antennas mounted on the West Tower of the Sears Building
and these are the ones included in Table 11. WBEZ-FM is not a contributor to
the field intensity existing on the roof, since the WBEZ antenna is hundreds
of feet below the level of the roof.
Table 12 provides the results of field measurements for the television
broadcast band. WCIU (26) was responsible for most of the far-field equivalent
power density measured on the 50th floor, contributing 33.2 yW/cm2 toward a
total of 34.2 yW/cm2 for all of the TV channels measured. It is only a minor
contributor to the total power density, 29 yW/cm2, at the roof location due to
TV transmission. Two of the major contributors, WLS (7) and WTTW (11) are
located on the West Tower of the Sears Building. The other TV stations are
located on the roof of the Hancock Building, roughly 1 mile distant and at a
height which places them above the levels of the Sears Tower roof.
20
-------
Table 13 presents the results of measurements made in a 39th floor
office of the Federal Building. The power density contributions from TV and
FM bands are 0.73 uW/cm2 and 5.74 yW/cm2, respectively, with the primary
contributors being WCIU (26) and WBEZ-FM.
The measurements were made under conditions which attempted to maximize
the power density existing at the windows of the offices in the Sears Tower
and the Federal Building; i.e., the blinds were raised, and measurements were
made near the windows. The levels measured would be expected to be signifi-
cantly reduced if the blinds had been lowered and closed.
21
-------
TABLE 10. SEARS TOWER
MEASURED ELECTRIC FIELD INTENSITIES FROM FM RADIO; 50TH FLOOR OFFICE
Station
Index
E(V/m)
Horizontal Vertical
;total
(V/m)
S(yW/cm2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Total S(uW/cm2)
0.012
0.015
0.054
0.17
0.24
0.27
0.12
0.43
0.60
0.27
0.24
0.24
0.068
0.27
0.095
0.17
0.30
0.034
0.0043
0.19
0.054
6.76
0.027
0.013
0.076
0.060
0.043
0.060
0.17
0.12
0.19
0.12
0.095
0.060
0.054
0.076
0.060
0.076
0.085
0.043
0.0024
0.085
0.048
8.51
.0295
.0203
.0929
.178
.244
.276
.208
.443
.632
.295
.258
.247
.0863
.280
.113
.186
.314
.0545
.00489
.209
.0719
10.9
0.00023
0.00011
0.0023
0.0084
0.016
0.020
0.011
0.052
0.11
0.023
0.018
0.016
0.0020
0.021
0.0034
0.0092
0.026
0.00079
0.0000064
0.012
0.0014
31.3
31.7
22
-------
TABLE 11. SEARS TOWER
MEASURED ELECTRIC FIELD INTENSITIES FROM FM RADIO; ROOF
Station
Index
E(V/m)
Horizontal Vertical
'total
(V/m)
S(yW/cm2)
1
2
3
4
11.1
6.24
7.94
9.12
9.89
9.89
9.81
13.2
14.9
11.7
11.9
16.0
58.6
36.2
37.8
68.2
Total S
200.8
23
-------
TABLE 12 SEARS TOWER
MEASURED ELECTRIC FIELD INTENSITIES FROM TELEVISION
Station
50th Floor Office
E(V/m) S(viW/cm2)
Roof
E(V/m) S(uW/cm2)
WBBM (2)
Visual Carrier 0.78
Aural Carrier 0.87
WMAQ (5)
Visual Carrier 0.62
Aural Carrier 0.19
WLS (7)
Visual Carrier 0.082
Aural Carrier 0.073
W6N (9)
Visual Carrier 0.87
Aural Carrier 0.28
WTTW (11)
Visual Carrier 0.030
Aural Carrier 0.030
WCIU (26)
Visual Carrier 10.0
Aural Carrier 5.01
WFLD (32)
Visual Carrier 0.96
Aural Carrier 0.48
WSNS (44)
Visual Carrier 0.34
Aural Carrier 0.27
Total S
0.16
0.20
0.10
0.010
0.0018
0.0014
0.20
0.020
0.00023
0.00023
26.5
6.66
0.24
0.061
0.031
0.020
34.2
0.22
0.25
0.55
0.19
9.23
1.64
0.98
0.28
2.09
1.17
0.63
0.20
1.78
0.54
3.05
1.08
0.013
0.016
0.080
0.010
22.6
0.71
0.25
0.020
1.16
0.37
0.11
0.011
0.84
0.076
2.48
0.31
29.0
24
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TABLE 13. FEDERAL BUILDING (39TH FLOOR OFFICE)
MEASURED ELECTRIC FIELD INTENSITIES - TV AND FM
Station
TV
WBBM (2)
WMAQ (5)
WLS (7)
WGN (9)
WTTW (11)
WCIU (26)
WFLD (32)*
WSNS (44)*
E(V/m)
Visual Aural
0.14
0.062
0.18
0.062
0.066
1.58
0.078
0.025
0.082
0.035
0.052
0.40
S(yW/cm2)
0.0067
0.0012
0.011
0.0013
0.0019
0.71
Total S
0.73
FM
#1
#2
#3
#4
Horizontal Vertical
3.51
0.62
1.12
1.29
2.51
0.14
0.25
1.02
4.56
0.11
0.35
0.72
Total S
5.74
*Not transmitting at time of measurement.
25
-------
San Diego
Electric field intensity measurements were made in a 17th floor office of
the Home Tower building in downtown San Diego. The 18 story Home Tower is
directly across the street from the Bank of America Building where the transmitting
antenna for KITT-FM radio is located. KITT-FM operates at a frequency of
105.1 MHz with a total effective radiated power (ERP) of 151 kW (120 kW
horizontal polarization + 31 kW vertical polarization.) The west side of the
Home Tower, facing the station, was estimated to be about 193 feet from the
antenna through use of a street map. A distance of 207 feet was measured with
an optical range finder.
The 17th floor office in the Home Tower is directly opposite the second
bay (from the bottom) of the 8 bay KITT antenna. For the 200 ft. separation
distance, it was expected that the power density existing at the Home Tower
office would be greater than 300 yW/cm2. Instead, measurements made, using
the dipole antenna and spectrum analyzer, indicated a power density of
0.211 yW/cm2, a factor of at least 1.5xl03, or 31.8 dB, lower than expected.
Measurements made on the roof of the Home Tower, at a location about 40 to 50
feet further away because of the roof layout and with no intervening structures,
yielded a total power density of 180 yW/cm2.
The NBS EDM-3, previously described, was also used for these roof measure-
ments. A value of electric field energy density equivalent to a power density
of 126 yW/cm2 was obtained, indicating a difference of + 1.6 dB between the
spectrum analyzer system and the EDM-3. It was noted, using the EDM-3, that
the field along the location of the dipole antenna used in this measurement,
but with the dipole removed, was non-uniform. Another measurement location
adjacent to the first was found at which the field, again using the EDM-3,
appeared to be quite uniform over a distance that the dipole antenna would
occupy. At this location, measurements made using both systems resulted in
indicated power densities of 119 yW/cm2 and 162 yW/cm2 for the spectrum analyzer
system and EDM-3, respectively. The relative difference in indicated power
density between the spectrum analyzer system and EDM-3 was -1.3 dB. On the
basis of these two sets of measurements, it is not possible to resolve the
differences between the two measurement techniques.
26
-------
The pertinent results of the measurements at the Home Tower are summarized
in Table 14. The fact that the power density existing inside the building,
0.211 yW/cm2, was so much less than the expected value of about 320 uW/cm2,
was very surprising. However, it was later found that windows on the west
side of the Home Tower, starting at the llth floor and continuing up through
the 18th floor, have a metallized mylar film applied to them to reduce solar
heat loading in the building.
This film, consisting of a mylar substrate coated with a thin aluminum
film, reflects sufficient light to signficantly reduce heat input to a building
due to incident sunlight, but still retains excellent visual transparency.
Being electrically conductive, it would also be expected to have RF shielding
properties. Based on the measurements made in the 17th floor office and a
comparison with the expected power density, it appears that the shielding
effectiveness of the film may be about 30 dB. However, estimates of power
densities in buildings are complicated by factors such as possible non-uniformity
in the azimuthal radiation pattern of the antenna and possible shielding by
the structure of a part of the RF radiation being transmitted because of the
extended area of the antenna. Such RF shielding properties in a relatively
inexpensive material, normally used to reduce heat loading without being
opaque, suggests a possibility for an easy and inexpensive method to alleviate
situations of excessive exposure levels in buildings for either persons or
electronic equipment susceptible to radiofrequency interference.
27
-------
TABLE 14. HOME TOWER
MEASUREMENTS OF ELECTRIC FIELD INTENSITIES FROM KITT-FM
Measurement Location E(dByV/m) Et . ,(V/m) S(yW/cm2)
Horizontal Vertical Ml
17th floor 117 115 .912 .22
Roof location 1* 143 147 26.1 180.3
Roof location 2** 141 145 21.2 119.0
*NBS EDM-3 probe reading: 2.1 nJ/m3 = 126 yW/cm2.
**NBS EDM-3 probe reading: 2.7 nJ/m3 = 162 yW/cm2.
28
-------
Houston
The 100 Milan Building is a high rise office building located extremely
close to two other high rise buildings whose roofs support the antennas for
one UHF television and nine FM radio stations. Located atop the Tenneco
Building, at a measured distance of 25.6 meters from the Mi lam Building is the
antenna of KLEF-FM, a 200 kW station. Approximately 205 meters from the Mi lam
Building is One Shell Plaza which supports 8 high power FM radio stations and
KVRL, channel 26, a 3196 kW UHF-TV station. Measurements of electric field
intensity were performed in a 47th floor office area of the Mi lam Building
facing the KLEF antenna. The measurement location is thought to be near the
maximum intensity of the KLEF radiation pattern. The measurement results
consisting of the individual stations and their measured contributions to the
RF field intensity and power density are presented in Table 15. A total power
density of 68 yW/cm2 was determined to exist at the measurement location.
KLEF contributed 33.8 yW/cm2, KVRL was responsible for 31.6 yW/cm2, and the
remaining eight FM radio stations on One Shell Tower together produced
2.0 yW/cm2 of the total.
It is of interest to note that the measured power density of 34 yW/cm2
produced by KLEF is 14.3 dB below the expected power density of 923 yW/cm2
which is determined by a calculation using the far-field effective radiated
power (76 kW) based on transmitter power and far-field gain of the antenna.
If the 12 bay, 33 meter long KLEF antenna is modeled as a vertically stacked
array of half-wave dipole elements, a careful calculation of the field along
the axis of the center of radiation reveals that the array exhibits significant
near field gain compression at a distance of 25.6 meters, being about 15dB
below the array's far field value. The modeled gain compression as a function
of distance from the array is shown in figure 2. It is seen that the measurement
location, 25 meters distant from the antenna, was in the near field. The
measured value of gain compression, based on the comparison of measured power
density and calculated far field power density, is -14.3 dB. The calculated
gain compression derived from figure 2 is about -15 dB.
29
-------
TABLE 15. MILAM BUILDING
MEASURED ELECTRIC FIELD INTENSITIES, 47TH FLOOR
Station Frequency EPR* E(dByV/m)
(MHz) (kW) Horizontal Vertical
E(V/m) S(yW/cm2)
KLEF-FM
KYND-FM
KRLY-FM
KIKK-FM
KODA-FM
KILT-FM
KLOL-FM
KMJQ-FM
KRBR-FM
KVRL-TV
Total S
94.
92.
93.
95.
99,
100.
101,
102,
104,
Ch.26
76**
194
194
96
194
200
194
200
192
3196
135.6
115.6
118.6
107
112
112
117
105
111
139.0
139.6
123.6
123
112
103
108
109
114
105
136.0
11.3
1.63
1.74
.489
.453
.504
.816
.570
.425
10.9
33.8
.704
.800
.063
.054
.067
.177
.086
.048
31.6
67.5
*The total effective radiation power of horizontal and vertical polarization
components.
**Station was operating at a reduced power of 76 kW total power in both
horizontal and vertical polarizations due to technical difficulties.
30
-------
NEflR FIELD OflIN COMPRESSION
N » 12
CO
Q
-10
to
to
-20
o
u
z
<
-30
-40
10 100
DISTANCE FROM ARRAY METERS
-I—I—> t It
1000
Figure 2. Near field gain compression for a 12 bay dipole array
-------
The TV and FM stations on One Shell Tower would be expected to produce a
total power density of 882 yW/cm2, 605 yW/cm2 from KVRL (26) and 277 yW/cmz
from all of the FM's, at the measurement location if that location were in the
maximum intensity of the radiation patterns (both vertically and azimuthally)
and there were no obstructions in the path of direct line of sight. The
measured power densities of 31.6 yW/cm2 and 2.0 yW/cm2 for the TV and FM
transmitters, respectively, are consistent with the real situation in that the
conditions which would be expected to produce the higher power densities,
i.e., on axis main beam exposures, do not exist at the measurement location.
A test was performed to try to determine the attenuation effectiveness of
two kinds of solar reflective films upon application to the windows. The
windows in the Mi lam building had no reflective films or conductive coatings
on them. Using the NBS EDM-3 because of the small size of the probe's sensitive
volume, measurements were made of the total field intensity with and without a
large piece of reflective film taped to one of the windows. The measurements
did not quantitatively determine the signal attenuation produced because the
film was so effective that the signals were attenuated to a level below the
EDM-3 sensitivity when the film was in place. This is in good agreement with
the earlier experiences in both San Diego and New York and confirmed the
feeling that solar reflective film may be effectively used to attenuate FM
broadcast band signals.
A final observation, using the EDM-3, provided a demonstration of the
enhancement insight of localized electric fields due to conducting structures.
It was found that local fields very near conducting structures, such as the
metallic leg of an office desk, could be at least a factor of 10 greater than
the general ambient environment in terms of the electric field energy density.
32
-------
CONCLUSIONS
These measurements confirm that there is the potential for relatively
high radiofrequency field intensities to exist within the upper floors of tall
buildings which are irradiated by main beam radiation from FM radio and TV
broadcast antennas. Measurements of polarization components in two orthogonal
planes have shown the existence of electric field intensities as great as 19
V/m in a high rise building about one block from an FM transmitter, and 10 V/m
due to a TV transmitting antenna several blocks from the measurement location.
No buildings were found in which the maximum exposure, the total power density
from all significant signals, exceeded a value of 100 uW/cm2. Consideration
of the attenuation effects of the electrically conductive film used in the
Empire State Building, the shielding effectiveness of the solar film used on
some windows in the Home Tower (San Diego), and the attenuation observed in
the Houston test indicates that the use of electrically conductive films on
windows is effective in reducing field intensities inside a building due to FM
radio transmission. The use of solar reflective films appears to have the
additional advantage of being a relatively inexpensive, but effective, means
to reduce electric field intensities inside buildings.
The interesting effect of near field gain compression was observed in
measurements in which the field intensity at distances very close to an FM
antenna array were found to be significantly lower than that predicted by
using the far field effective radiated power of the array. An analysis of the
near field gain characteristics of the array is in agreement with the measurement.
This observation is significant for estimating close-in fields from extended
arrays with a large number of elements. The near-field field intensity appears
to be as much as 14 dB below the value predicted on the basis of far field
concepts at a distance of 26 meters for a 12 bay FM antenna.
33
-------
A half-wave dipole antenna was used to sense the fields and the possible
alteration of antenna calibrations because of use in an inside building environment
has not been investigated. In particular, the use of a half-wave dipole in
the near field of FM radio transmitting antennas should be examined from the
point of view of spatial resolution of the incident electric field. The
complex configuration of the fields within any reflective volume, such as the
102nd floor ESB observatory, will exhibit variations in intensity which may be
unresolvable with a tuned dipole because of its physical size. It is conceivable
then that certain "hot spots" might not be able to be accurately identified
and measured by using tuned dipoles, at least at 100 MHz since at this frequency
the wavelength is 3 meters.
It was found that various metallic objects can create intensified local
fields very near them, sometimes leading to field intensities 10 times greater
than the local ambient value. Additional study of this phenomenon is indicated.
34
-------
REFERENCES
Tell, R.A., N.N. Hankin, J.C. Nelson, T.W. Athey, and D.E. Janes, "An Automated
Measurement System for Determining Environmental Radiofrequency Field
Intensities: II," Measurements for the Safe Use of Radiation, editor,
S.P. Fivosinsky, National Bureau of Standards Special Publication 456,
pp. 203-213, Washington, DC, November 1976.
Tell, R.A. and P.O. O'Brien, "An Investigation of Broadcast Radiation Intensities
at Mt. Wilson, California," U.S. EPA Technical Note ORP/EAD-77-2, April
1977.
Bowman, R.R., "Some Recent Developments in the Characterization and Measurement
of Hazardous Electromagnetic Fields," in Biologic Effects and Health Hazards
of Microwave Radiation, Proceedings of an international symposium, Warsaw,
October 15-18, 1973, published by Polish Medical Publishers, Warsaw,
1974.
35
-------
Office of Radiation Programs Technical Publications
Nonionizing Radiation
Publications of the Office of Radiation Programs are available
from the National Technical Information Service (NTIS), Springfield,
VA 22161. Current prices should be obtained directly from NTIS
using the indicated NTIS Order number. Single copies of some of
the publications listed below may also be available without
charge from the Office of Radiation Programs (AW-461), 401 M St.,
SW Washington, DC 20460.
EPA ORP/SID 72-3
EPA/ORP 73-2
EPA-520/2-73-001
EPA-520/1-74-005
EPA-520/2-74-008
ORP/EAD 75-1
ORP/EAD.-76-1
ORP/EAD-76-2
EPA-520/2-76-008
ORP/EAD-77-2
Reference Data for Radiofrequency Emission
Hazard Analysis (NTIS Order No. PB 220 471)
Environmental Exposure to Nonionizing
Radiation, (Available NTIS only, Order
No. PB 220 851)
Nonionizing Measurement Capabilities: State
and Federal Agencies (Available NTIS only,
Order No. PB 226 778/AS)
RF Pulse Spectral Measurements in the
Vicinity of Several ATC Radars (NTIS Order
No. PB 235 733)
An Evaluation of Satellite Communication
Systems as Sources of Environmental Micro-
wave Radiation (NTIS Order No. PB 257 138/AS)
An Analysis of Broadcast Radiation Levels
in Hawaii (NTIS Order No. PB 261 316/AS)
Radiation Characteristics of Traffic Radar
Systems (NTIS Order No. PB 257 077/AS)
A Measurement of RF Field Intensities in
the Immediate Vicinity of an FM Broadcast
Station Antenna (NTIS Order No. PB 257 698/AS)
An Examination of Electric Fields Under EHV
Overhead Power Transmission Lines (NTIS
Order No. PB 270 613/AS)
An Investigation of Broadcast Radiation
Intensities at Mt. Wilson, California
(NTIS Order No. PB 275 040/AS)
ORP/EAD-77-3
An Analysis of Radar Exposure in the San
Francisco Area (NTIS Order No. PB 273 188/AS)
-------
EPA-520/2-77-008
ORP/EAD 78-1
ORP/EAD 78-2
ORP/EAD 78-3
ORP/EAD 78-4
Radiofrequency Radiation Levels and Population
Exposure in Urban Areas of the Eastern United
States
A Comparison of Measurement Techniques to
Determine Electric Fields and Magnetic Flux
Under EHV Overhead Power Transmission Lines
An Analysis of Radiofrequency and Microwave
Absorption Data with Consideration of Thermal
Safety Standards
Measurements of Radiofrequency Field Intensity
in Buildings with Close Proximity to Broadcast
Stations
Near-Field Radiation Properties of Simple
Linear Antennas with Applications to Radio-
frequency Hazards and Broadcasting
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Measurements of Radiofrequency Field Intensity in
Buildings with Close Proximity to Broadcast Stations
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Richard A. Tell and Norbert N. Hankin
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Electromagnetic Radiation Analysis Branch
Office of Radiation Programs, LVF
U.S. Environmental Protection Agency
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
fPONSORING AGENCY NAME AND ADDRESS
lectromagnetic Radiation Analysis Branch
Office of Radiation Programs, LVF
U.S. Environmental Protection Agency
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
This report summarizes the results of a series of radiofrequency field intensity
measurements made in eight tall buildings located in New York, Miami, Chicago, San
Diego, and Houston. The buildings, in which the measurements were made, were selected
because of their proximity to FM radio and/or VHF and UHF television transmitting
antennas. These broadcast antennas were usually located on nearby buildings' so that
the possibility existed for high intensity illumination of the upper floors of the
buildings selected by the main beam of radiation of the antennas. The principal
objective in conducting these measurements was to obtain information about the field
intensities which can be produced by broadcast antennas at locations close to the
antennas and near the main beam axis. In addition, the measurements help in determin-
ing the higher level radiofrequency exposures of persons who work and live in tall
buildings under similar irradiation situations, and in developing techniques which
allow estimates to be made of exposures under such conditions.
The maximum power densities derived from electric field intensity measurements
in any of the eight buildings were less than 100 microwatts per square centimeter
(yW/cm ). Higher exposures were observed at unobstructed locations on roofs of some
of the buildings. Observations about factors which were found to affect exposure
levels are discussed.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (R«»-4-77) PREVIOUS EDITION is OBSOLETE
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