United States Office of
Environmental Protection Radiation Programs
Agency Washington, D.C. 20460
ORP/EAD-75-1
August 1975
Radiation
Technical Note
An Analysis of
Broadcast Radiation
-------
Technical Note
ORP/EAD 75-1
AN ANALYSIS OF BROADCAST RADIATION LEVELS IN HAWAII
RICHARD A. TELL
August 1975
U.S. Environmental Protection Agency
Office of Radiation Programs
Washington, DC 20460
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1 Contents
Page
Contents . ._'..'. ................ . , . . . ..." . . . i
List of Tables . .'.... . . . , ... . . . . . , . . ii
List of Figures ..........,/........ iii
Introduction .. . . . . . ... . . . . , . . , ... . . . . . . ... 1
Broadcast Sources ........................ 2
. - - {. ' -
Population Estimates 6
Methods and Results of Field Calculations . . . . , . . . .... 9
Predicted Levels . . .... .......... ... . . . ... . 21
Standards . ..................... . . . . . . 24
Conclusions and Recommendations . . . . . . . . ».. . .... .... 29
References . . .................... 33
Appendix 35
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List of. Tables
Table Page
1 AM Stations in Honolulu .3
2 FM Stations in Honolulu ........ 4
3 TV Stations in Honolulu ........... 5
4 TV Stations on Hawaii and Maui . . . 7
5 Broadcast Band Allocations and Maximum
Authorized Powers 8
6 CEDs, Housing Units and Population Around the
KGMB-TV, KHET-TV, KGMQ-FM Broadcast Installation .... 10
7 CEDs, Housing Units and Population Around the
KIKU-TV, KUMU-FM Broadcast Installation . 11
8 CEDs, Housing Units and Population Around the
KGU, KKUA, KTRG Broadcast Installation, ......... 12
9 Calculated Exposures from Honolulu FM and
TV Stations . 19
10 Calculated Exposures from Hawaii and Maui
TV Stations 20
11 Maximum Recommended Levels for Human Exposure 28
11
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List of Figures
Figure Page
1 Ground Level Field Strength for KGU ,' .......... 13
2 Vertical Radiation Pattern for a UHF-TV
Transmitting Antenna . ...... . . ..... .... 15
3 Power Density and Field Strength in Free Space
4 Maximum Power Density as a Function of Distance
for Several FM and TV Broadcast Stations in Honolulu . . 25
5 Some Selected Microwave Exposure Standards . . . . . . . 26
iii
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An Analysis of Broadcast Radiation Levels in Hawaii
Introduction
;The Office of Radiation Programs conducts a nationwide program of
monitoring and assessment of radiofrequency and microwave radiation
levels as they relate to the potential for hazards in the environment.
This study was initiated at the request of the Hawaiian State Department
of Health and is intended to address the possible harmful radiation1
effects from broadcast installations in the state of Hawaii. Local news
media in Hawaii have carried a number of articles (1-3) pertaining to
possible dangers arising from the presence of certain broadcast towers.
A State Senate concurrent resolution has instructed theistate Health
Department to study this question and report its findings by November 1,
1975 (4). :
,Due to the limited time available and the desire for a rapid :
analysis, this report is necessarily brief. Additionally, the data on
station locations and technical operating parameters have not been
subjected to exhaustive verification; consequently the reported
inventories of broadcast stations are as accurate as possible but may
not be exact. Every effort, within time constraints and reason, has
been expended to ensure the maximum reliability of the data and
calculations.
The purpose of this report is to theoretically examine the various
broadcast installations within Hawaii and to determine the potential
for hazardous exposure situations in the vicinity of the various towers.
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2
Most sources of interest are within the city of Honolulu itself, but
several are located on other islands. .Broadcast radiation safety has
been generally examined previously (5J and this report considers pre-
dicted field intensities which could exist around different stations.
Technical information on station transmitting facilities are used to
calculate worst case expected field intensities for AM, FM, and TV
stations both at ground level and at elevated locations near towers.
Calculated values of exposure are qualitatively evaluated in terms of
previous measurement projects at other broadcast stations located on
the mainland. The population residing in the vicinity of selected
transmitting sites is presented and the results of the field calcula-
tions are discussed in terms of RF exposure standards and the potential
for associated effects.
Broadcast Sources
An inventory of the various broadcast stations of interest was
prepared by referring to a number of different information sources
(6-10) as well as reviewing, directly, selected station files at FCC
headquarters in Washington, DC. On the basis of this search, listings
of stations in Honolulu were prepared and are presented for AM standard
broadcast in Table 1, for FM broadcast in Table 2, and television
broadcast in Table 3. These tables incorporate the information from
all sources above and information supplied by personnel of the State
Health Department. There are 17 AM radio stations ranging in trans-
mitter power from 1 to 10 kW, 8 FM radio stations ranging in
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Table 1
AM STATIONS IN HONOLULU
CALL
KAIM
KCCN
K6MB
KGU
Power
KHVH
KIKI
KISA
KKUA
KLEI
KNDI
KOHO
KORLn/
KPOll/
KUMU
KZOO
5
5
5
10
5
5
10
5
10
10
5
5
10
5
5
5
1
Freq
(kHZ)
870
1420
590
760
1040
830
1540
690
1130
1270
1170
650
1380
990
1500
1210
Antenna
Height
(Ft):
220
154
270,
270
270
270
154
270
220
182
220
270
400
v220
270
LAT
21-17-08
21-19-27
21-17-59
21-17-41
21-17-59
21-17-59
21-19-27
2-1-17-41
21-23-54
21-12-29
21-17-08
21-17-59
21-17-28
21-17-43
21-17-08
21-17-59
LONG'r-1-")
157-48-08
157-52-47
157-51-33
157-51-49
157-51-33
157-51-33
157-52-47
157-51-49
157-47-34
157-55-59
157-48-08
157-51-33
157-50-20
157-51-49
157-48-08
157-51-33
H/
Effective Field-'
[mV/m/kW]
175 F/
178 G/
175 D/
185 E_/
180 p_/
175 D/
183 G/
182 E/
191
191
175 £/
175 D_/
257
183 F/
184 D/
'Not sure of coordinates. , -
I/Present operation; proposed to change to: 21-17>59N, 157-.50-20W, with effective field - 203 mV/m/kW,
with antenna height of 270 ft.
£/Not sure whether presently operating.
P/,£/,F/,G/stations with same footnote share a common tower.
H/Field strength at 1 mile per kW input power. ,.
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CALL
POWER (kW)
FREQ (MHz)
Table 2
FM STATIONS IN HONOLULU
ANTENNA HEIGHT (FT)
ABOVE GROUND
LAT (°- '-"')
LONG
KAIM
KGMQ^/
KKAI
KPOI.
KTUH^
KULA
R/
KUMIF7
KHSS^-7
37
100
25
35
10 W
60
60
100
95.5
93.1
96.3
97.5
90.5
92.3
94.7
_
224
337
70
400
68^106
245
c/
165k/326
76^472
21-17-08
21-17-46
21-23-57
21-17-28
21-18-11
21-26-43
21-17-07
-
157-48-08 AM
-*
157-50-36 TV
157-44-46 -
157-50-20 AM
157-49-21
158-03-49
157-50-24 TV
'
^Educational.
£/Use circular polarization.
C^/Heights above roof where tower is located on a building.
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Table 3
TV STATIONS IN HONOLULU
CALL CHANNEL POWER (kW) ANTENNA HEIGHT LAT («-'-") LONG (°-'-")
VISUAL AURAL ABOVE GROUND (FT)
KHON
KITV
KGMB
KIKU
KHET
2
4
9
13
11
60.3
100
209
30.7
148
12.6
20
29.5
6.17
29.5
350
365
436
371
436
21-17-45
21-17-44
21-17-45.7
21-17-07
21-17-45.7
157-51-12
157-51-06
157-50-35.7
157-50-24
157-50-35.7
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6
effective radiated power (ERP) from 10W (an educational station) to 100
kW which is the maximum authorized power for FM use, and 5 TV stations
which range between 37 and 239 kW of ERP. For TV stations both visual
and aural ERP is listed. Table 4 lists the TV stations in other parts
of Hawaii. The height of the transmitting antenna above ground is given
for TV stations, while for FM stations the antenna height above roof
level is also shown when the tower is located on a building rather than \
''.)'
on the ground. Table 5 gives the band allocations for the various broad-
cast services and maximum authorized powers which may be used by some
stations. There are no UHF TV stations in the state of Hawaii.
A number of stations in Honolulu share common towers for their
antennas or antenna supports. Of the 30 stations listed within Honolulu
there are apparently only 16 physically separate locations for trans-
mitting antennas. For example, five different AM stations share d
single common tower in their operations and at one location two TV
stations and one FM station share the use of a common tower. Honolulu
has a large number of tall buildings of nearly equal height with broad-
cast antennas atop several of them. This is not a unique situation
when compared to some other metropolitan areas on the mainland.
Population Estimates
Coupled with the relatively high density of broadcast installations
is a relatively high population density in the immediate Honolulu area.
As a means of establishing the population in the area of interest, the
population was estimated around three tower sites using a computerized
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Call
Channel Power (kW)
Visual Aural
KHAN
KHVO
KPUA
KAII
KMAU
KMVI
KMEB
11
13
9
7
3
12
10
2.09
4.68
1.00
29.8
14.1
30.0
30.9
0.275
1.59
0.50
' 1
5.89
2.69
4.36
6.17
Table 4
TV Stations on Hawaii- -
* -**
' >
Antenna Height
Above Ground (Ft)
80
80
258
TV Stations on Maui
75
60
100
47-
Lat (°-'-
19-43-56
19-43-57
19-43-00
20-42-41
20-42-41
20-42-43 >
20-42-40
Long (°-'-")
155-04-09
155-04-04 .-
155-08-13
156-15-26
156-15-35 '
156-15-26
156-15-34
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8
Table 5
Broadcast Band Allocations and Maximum Authorized Powers
Service Frequency Range Maximum Authorized
(MHz) Power (kW).
Am Standard Broadcast 0.55-1.6 50
FM 88-108 100*
Low VHF TV 54-88 100
High VHF TV 174-216 316
UHF TV 490-893 5000
*In each polarization plane.
census data base. This method has been used previously (11) -to
determine population exposure to AM radio stations. In this case, the
population residing within given distances out to a maximum range of
5 miles was computed for three broadcast locations: (a) the KGMB-TV,
KHET-TV, and K6MQ-FM site, (b) the KIKU-TV and KUMU-FM site, and (c)
the KGU AM radio site. Table 6 presents the number of census
enumeration districts (CEDs), the number of housing units, and the
total population computed via the program for site (a) above. Tables
7 and 8 provide similar data for sites (b) and (c). These estimates
show populations of 41,363, 28,610, and 2,449 residing within one mile
of sites a, b, and c above. Population values based on a small number
of CEDs must be considered approximate but values associated with more
than 10 CEDs are probably quite accurate. These population numbers do
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9
not include transient fluctuations which occur during the day nor
nonresidents.
Methods and Results of Field Calculations
AM Standard Broadcast
AM radio stations employ vertical polarization in transmission
using vertical towers typically situated over ground, but infrequently,
towers are located on building roofs. The entire tower is the radiating
element in AM broadcast and produces a ground wave field at locations
about it. All AM stations in Hawaii utilize single monopole types of
antennas and have non-directional radiation patterns. Based on the
tower's height, the transmitter output power, and ground conductivity
at the assigned frequency, the electric field strength can be computed
via analytical techniques. Using one such technique (12) the ground
level field strength was computed for KGU AM and is shown in Figure 1
as a function of distance out to 5 km. At the point of minimum distance
for which calculations were made (100 meters) a field strength of 9.3
V/m was found. Because at one location, indicated by footnote D in
Table 1, 5 stations use the same tower, a maximum expected equivalent
power density was computed as 57.8 yW/cm2. In this computation the five
5 kW stations have been assumed to have an effective field at one mile
of 185 mV/m/kW and to be on a frequency of 760 kHz with a ground con-
ductivity of 15 m mhos/m, with a 270' high tower.
FM and TV Transmissions
FM and TV stations normally employ transmitting antennas which
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Table 6
CEDs, Housing Units and Population Around the
KGMB-TV, KHET-TV,-KGMQ-FM Broadcast InstallationA/
,6
,7
Miles
0.1
0.2
0.3
0.4
0.5
0.
0.
0.8
0.9
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
CEDs
1
2
5
8
15
20
22
31
38
46
78
107
140
186
213
244
255
262
Housing Units
383
547
1750
2796
5983
8855
9301
13107
15542
19160
32170
42312
52240
64008
73312
82463
86382
88271
Population
765
1170
3323
5942
11990
18765
19894
28134
33810
41363
72472
99572-
131078
172740
206932
242636
258346
266664
A/Based on 1970 Census data.
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Table 7
CEDs, Housing Units and Population Around the
KIKU-TV, KUMU-FM Broadcast Installation*/
Miles
0.1
0.2
0.3
0.4
0.5
0.6
0;7
0.8
0.9
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
CEDs
0
0
1
5
9
12
15
20
24
33
59
99
130
165
202
221
236
256
Housing Units
0
0
0
2138
3659
5070
6155
8029
10138
14195
24798
39972
48233
59025
69854
75743
80909
86239
Population
0
0
47
3415
5882
8373
10579
15416
20344
28610
54757
94303
119751
154544
193322
215180
234476
256834
A/Based on 1970 Census data.
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Table 8
CEDs, Housing Units and Population Around the
KGU, KKUA, KTR6 Broadcast Installation*!/
Miles
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
CEDs
0
1
1
1
2
2
2
3
4
4
26
68
109
147
176
213
243
262
Housing Units
0
0
0
0
279
279
.27?
1025
1144
1144
9424
25439
39894
53239
62502
72362
80879
88122
Population
0
314
314
314
837
837
837
2186
2449
2449
19423
54228
96006
137943
170515
206644
240464
268496
ro
A/Based on 1970 Census data.
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13
. - , \ Distance from Tower (km) - . ;
Figure 1 Ground Level Field Strength for KGU, Honolulu, Hawaii
'10 kW, 760 kHz, e=15, o=15, Tower Height=270', Vertical Polarization
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14
are elevated high above ground to increase their coverage; the mode of
propagation differs from that used by AM stations. In the case of FM
or TV transmission the antenna radiates the signal while the tower acts
only as a supporting structure. In certain instances FM and TV stations
use an existing AM radio or TV tower to support their antennas. Gener-
ally the FM and TV antennas exhibit a uniform pattern in the azimuth
while they tend to concentrate the radiated power in a confined vertical
beamwidth, pointed near the horizon. In this fashion, the antenna
exhibits gain above an isotropic radiator and allows the station to use
less power to produce a higher ERP. The vertical beamwidth depends on
the size of the particular antenna and the frequency. In the case of
UHF TV this beamwidth becomes very small as seen in Figure 2. With FM
: '* .
and VHF TV antennas this vertical plane pattern becomes broader. In
Figure 2 the ordinate represents the relative field strength (relative
to the main beam value) which will occur at various depression angles.
To fully assess the radiation intensities near FM and TV
transmitting antennas, a complete knowledge of the vertical radiation
pattern is required. Unfortunately this data is rarely available for
depression angles greater than 15-20 degrees and thus it becomes very
difficult to accurately, compute radiation levels near the tower base.
There is an approach which can be used to assess maximum possible power
densities which is to calculate the worst case value. However, field
measurements are the only method to determine actual exposure levels.
In general, though, the maximum, worst case level calculated will not
be exceeded.
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15
i! POWER GAIN-24.0
HOR. GAIN-20.3
KMCU rKU MMIZONTAL FL/WZ
Figure 2 Vertical;Radiation Pattern for a UHF-TV
Transmitting Antenna
The power density in the^main beam of an FM or TV installation
may be computed as follows:
. 40mR2
where
ERP is the main beam effective^radiated-power in watts
R is sthe^distance from/therantenna-.'in meters
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16
Another convenient formula for computing the electric field strength of
a station is
R
When the vertical radiation pattern is known the ERP in the desired
direction should be substituted into the above formulas. In the absence
of the vertical pattern the maximum ERP has been used to compute power
densities for the Hawaiian FM and TV stations.
Also, when measurements1 are not available, to assist in the
hazard analysis, it must be assumed that the formation of standing wave
patterns is possible and that this effect will increase! the apparent
radiation exposure level. It is conventional to assume that a reflected
wave can add constructively with the incident wave and double the electric
field strength or increase the power density by a factor of four (13).
Power density and field strength are related by
W (W/m2) = E "i where
120ir represents the impedance of free space. Figure 3 illustrates this
relationship graphically. Thus, calculated main beam power densities
must be increased by 6 dB (a factor of 4) to account for possible
fnultipath effects on signal enhancement.
Generally the radiation pattern at extremely steep depression
angles, for example near 90° or straight down the tower, implies a very
Tow level of radiation relative to the main beam. However, it has been
observed, via field measurements, that intense levels of RF may occur
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17
2000
1000
100
I
1 I I i i i III I 1I I I I ill I 1 I I I I III 1 1I l l 1111 1 1| I' I 11 L
.001
.1 1
POKER DENSITY ( milliwatts centimeters' )
100
Figure 3 Field Strength and Power Density in Free Space
near the base of certain FM transmitting antennas (14) contrary to the
simple theory. This steep angle radiation is presumably due ,to the
particular configuration of radiating elements on various types of
k ' 'N ' . .
antennas. It is not clear whether this phenomena exists for commonly
used VHF TV transmitting-antennas or not. However, in the absence of
any definitive measurement data on TV antennas it is assumed, for the
purposes of this report, that VHF TV as well as FM antennas can exhibit
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. ;- "' 18 _ '*
this property. For a potential hazards analysts this assumption seems
appropriate until ft is shown to" 'be overly conservative through
measurements*
To analyze l^epossllftev radiation intensities around the FM
and TV transmitting install at tons:, calculations were performed for each
FM and TV statlion separately and for those combined fad If ties where ,
more; than oneTStatliorr exists. By referral to :FCC records (7) it was
possible to identify FM antennas which are located; on roofs of buildings
':' ' -
in addition to those situated On ground; based! towers. Thjs allowed the
calculation of power-density at roof level as-well as: at ground level.
In certain instances this; fnfprjraMonrwas-derived^ for TV stations also.
Additionally the distances from each FM andi TV station ih Honolulu were
computed at whfich tne maximum power dfensila? couildf be 0.1!, 1» and; 10
mW/cm2. All of- this data Is presented m Table 9 for Monol|uflu stations.
Table 1.0 contains similar idata for other TV stations i=n the state. Until
data on actual radiation patterns ts available;the distances listed for
given exposures in Tables 9 and; TQ must be oonsldered as applicable at
any vertical angle from the transmitting antenna and can be used to
establish areas in-which the exposure level may be as high as the given
value. For FM stations the.roof and/or ground level values have been
computed using: the ElP-fte the horizontal; pftane>only since experience
has shown that the: vertiea;lFl;y polarlied/field ts; very Tow in comparison
to the horUzohlafl component at-Jsteep depresMon anglesv. For the
' ' T i, '.
calculate on? of"distance to/various; powerdensities; for FM? stations,
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Table 9
Calculated Exposures from Honolulu FM and TV Stations-1^
Call
KAIM
KHSSl/
?kPOI
KTUHr
tKKAl ,
kULA
KHON-jy
kifv-Tv
KIKU-tV
KHET-TV
KGMB-TV,)
KHET-TV ,|
KGMQ-FM 1
KIKU-TV,]
KUMU-FM I
Power (kW)
37
TOO
100
35
10W
60
25
60
72.9
120
238.
36.
.5
.9
177.5
616
156,9
Distance (ft) to following
power dens i ties (mW/cm2)
0.1 ,1.0 10.0
356
828
828
346
6
641
293
453
491
641 -
904
355
780
1452
733
112.6
261
261
109.4
1.8
203
92.6
143
165
, 203
286
112
247
459
232
35.6
82.8
82.8
34.6
-
64.1
29.3
45.3
49.1
64.1
90.4
35.5
78.0
145
73.3
Power Density at
Roof level and/or
ground level-
(mW/cm2)
0.253
0.302
5.93/0.154
0.075
0.
1
0.
0.
0.
.193
.755/0.
.747
.342
.204
.308
0.430
0.301/0.092
0.320
1.052
1.056/0.285
-/Calculations employ main beam ERP and assume that the resultant field strength is twice the
simply computed free space value.
JL/Uses circular polarization.
C/Figures to left of a slash indicate roof level power densities.
-------
Table 10
Calculated Exposures from Hawaii and Mauf'TV Stations-'
A/
Hawaii
Call ".;'
-;-. , I
KHAW-TV
KHVprTV
KPUA-TV
Maui
KAII-TV
KM/\UVTV
KMVI-TV
KMEB-TV
Power (kW)
2.365
6V27
1 .50
35.69^
16?79
34.36
37.07
Distance (ft) to following Power Density at
power densities (mW/cm2) Roof level and/or.
0.1 1.0 10.0 ground level
(mW/cm2)
90.0
147
71.7
350 ~
240
343
356 v.
28.5
46.3
22.7
111
75.8
108
113
_9.00 ' 0.13
14.7 ,0.34-
7;. 17 ,0.01
c
35.0 2.17
24.0 ^1;60
34?3 1.18
35.6 ', -5.75
ro
o
i/Calculations employ main beam ERP and assume that the resultant field strength is twice the
simply computed free space value, !
-------
21 ' .. .'
the power in both polarization planes has been used since at locations
lateral to the tower-both components would add.
To properly assess the -implications of these distances with
respect to adjacent building exposure, a complete knowledge of .building
. . .' ' i ' ' '. .
heights and locations is required. Information on some of the taller.
buildings in Honolulu was provided by the State Health Department and
has been used to investigate situations where individuals,might be >r
exposed to relatively intense RF fields. The data on.buildings was not
necessarily complete, and the possibility remains that there exist other
locations not considered here where significant power densities;occur.
<. A simple approach for identifying, areas subject,to the
specified, maximum possible power densities is to envision a spherical
surface centered on the various transmitting antennas with a radius ,
equal to .the.distance associated with a given exposure level. The > ?
intersection-of this spherical surface.with nearby buildings can be ,
'.' i '' ' '
used to isolate specific areas ,of interest for more detailed analysis.
Predicted Levels
Inspection of Table 9 reveals that a computed power density as
high.as 6 mW/cm2 may exist on the roof of the Ala Moana Hotel which
supports the KHSS-FM transmitting antenna. A power density of 1.052
mW/cm2 is found at the base, of the KGMB-TV tower. In the case of multiple
station outlets the computed power density is found by adding all station
powers together. A ground level value of 1.7 mW/cm2 is predicted at
-------
22
the base of the KKAI-FM tower. In general, the values of power density
found at either roof level, or ground level are found to be in the
vicinity of 1 mW/cm2 or lower while at three locations the computed
values are above 1 mW/cm2 and one is near 6 mW/cm2. At no location is
the roof or ground level power density found to exceed 10 mW/cm2.
i."
Table 10 shows that maximum power densities of 0.01 to 5.75 mW/cm2
may exist near the tower bases of TV stations located on the islands of
Hawaii and Maui. Generally the highest power densities computed are
associated with relatively low antenna heights and relatively high power.
Low antenna heights are usually associated with an installation on a
tall building or mountain top where the antenna is normally elevated
just enough to avoid clutter in the immediate area; this clutter might
be air conditioning equipment or elevator shafts on a tall building or
trees on a mountain top. In such cases, it would not be unusual for
access to the base of the tower to be restricted, as on a roof, or
«
infrequently visited as on a remote mountain top.
Because of the difficulty in obtaining complete information on
building heights the following comments are presented on specific
building locations and associated exposure levels in order of decreasing
areas of interest:
Ala Moana Hotel - This is the site of KHSS-FM located on the
roof with a 76' tower. .Power densities on the roof could approach 6
mW/cm2. This station could possibly provide the highest proportion of
total exposure on the roof of the adjacent Ala Moana Building at 1441
-------
.:. ; , . . '23 ' . '
Kapiolani Blvd. This roof at 300 feet above ground could experience a,
power density of 0.4 mW/cm2 assuming that it is not more than 400 feet
away from the KHSS-FM antenna site. ;
KMEB-TV tower on Maui - This is the, location, of the lowest.
antenna for any FM or TV broadcast station in the state. Coupled with
" '' ~- f" ' ' ' ' ' '
37 kW of ERP the ground level power density could possibly reach 5.75
mW/cm2.;
t( KAII-TV and KMAU-TV towers on Maui - These two towers are close
to the ground and located within 0.1 mile of each other'on Mt. Haleakala.
Ground level power densities of 2.2 and 1.6 mW/cm2 were computed for
KAII and KMAU, respectively. : ^
; .-".''. ' - - - - . ;.'. , :
KlfAI-FM - Apparently located on a hill side with a 70' antenna
height;,, this station could produce a ground level power density a-t the
foot @f the tower of 1.7 mW/cm2.
/ KGMB^TV, KHET-TV, and KGMQ-RM - This transmitter site has the
highest concentration of ERP of any location within the state. A ground
I ' : . '.'' '. ' '<- '. . ' ' - .
level power density of 1.05mW/cm2 was computed at the base of the 365'
tov/er which supports the, antennas for the three stations. / ,
KfWI-TV tower on Maui -The antenna is ;]00f above ground .ori:
Haleakala Crater and could produce a ground level power density of
1.2 mW/cm2.
-------
24
Hawaiian Village Hotel - This is the site of the KIKU-TV and
KUMU-FM antenna tower at 371' above ground. A roof level power density
t
of 1.05 mW/cm2 and ground levels of 0.29 mW/cm2 are predicted.
A number of other building locations could be in areas at which
power densities in the. range of 0.1 and 1 mW/cm2 could occur but
$
definite information on their distance from nearby towers is necessary.
V,
Figure 4 is a graph of maximum power density from several of the more
powerful emitters in the source inventory vs. distance away in the main
beam.
Standards
Currently the only Federal RF standards in the U.S. are the
Occupational Safety and Health Administration (OSHA) standard (14) for
occupational exposure control and the Bureau of Radiological Hea.lth
(BRH) microwave oven performance standard (15). The OSHA standard is
10 mW/cm2 as averaged over any possible 0.1 hour period. This means
the following:
Power density: 10 mW/cm2 for periods of 0.1 hour or more
Energy density: 1 mW-hr/cm2 during any 0.1 hour period.
The BRH microwave oven standard specifies that any microwave oven must
not leak radiation exceeding a power density of 5 mW/cm2 at any point
two inches from the surface during the life time of the oven. Figure
5 illustrates the exposures allowed for various durations by different
exposure guides.
-------
25
100;
r
-r-
ions.
ior
i
CM
o
c
Ol
Q
$-
OJ
I
o.
I L_
.1L.
10
$ncl' tne
are 'double
100 1000
Distance from Tower (Ft)
Figure 4 Maximum Power Density as a Function of Distance for Several FM and
TV Broadcast Stations in Honolulu
-------
26
. ANSI. OSHA 110 MHZ-100 GHZI
U.S. ARMY-AIR FORCE (300 MHZ-300 GHZ)
(PRACTICAL ENFORCEMENT LlMlT.55 mW/cm2)
VACGIH UOOMHZ-IOOGHZt
BRH Microwave Oven
USSR I300MH2-300GHZ1
USSR NON OCCUPATIONAL (300AAH2-3CO GH2)
TIME OF EXPOSURE (m
Figure 5 Some Selected Microwave Exposure Standards
The standards are either occupational exposure standards or
product performance standards and are not necessarily applicable to
the general populace. However, the State of Texas has announced its
intention to develop standards for the protection of individuals and
is structuring its proposal in terms of the OSHA .standards (16). It
\ . ~
must be realized that the OSHA standard implies the ability to control
-------
/;.. '. . 27 ' ' ^
the exposure to workers and assumes prior knowledge of the health
conditions of workers. The health conditions of individuals and the
number of exposed must be taken into account and the overall impact on
potential risk evaluated before establishing a generally applicable
8'"' ' ' . .
environmental RF exposure standard. At the present stage of evalua-
tion, exposure levels over 10 mW/cm2 are considered as potentially
hazardous and should be reduced.
Exposure levels between 1 and 10 mW/cm2 are considered as
significant and such exposure situations should be documented in the
event that research indicates that a limiting criteria should be estab-
lished somewhere in this range. Exposure levels below 1 mW/cm2 are rather
prominent in the environment and at the present time there is no
scientific evidence of them being a hazard.
Other factors besides direct biological interactions must be
considered in evaluating RF hazards. A potentially important factor
is radiofrequency interference to various electronic equipments,
particularly critical life support devices such as cardiac pacers and
medical products used in hospitals. Interference to pacemaker opera-
''.' ' . " i" '
tion has been clinically observed from at least one patient due to a
UHF-TV broadcast installation (18) and an inside-the-hospital standard
of 1 V/m (0.26 yW/cm2) has been established in the University of
California Medical Center (19) due to the close proximity of a high
power broadcast installation. Table 11 illustrates some of the various |
RF exposure standards and points out the wide difference between these
-------
28
Table 11
Some RF/Microwave Exposure Standards
Standard
OSHA
ANSI
BRH
USAF
USSR
Applicable Frequency
Range
10 MHz - 100 GHz
10 MHz - 100 GHZ
915, 2450
300 MHz - 300 GHz
10 kHz - 10 MHz
Medium Waves
100 kHz - 3 MHz
3 - 30 MHz
30 - 50 MHz
50 - 300 MHz
0.3 - 300 GHZ
Limits and Comments
10 mW/cm2 for periods >0.1 hour
1 mW-hr/cm2 during any 0.1 hour
period
Same as OSHA but includes other
specifications for field as
40,000 V2/m2 or 0.25 A2/m2
i
5 mW/cm2 at any point two inches
from surface of microwave oven
during life time
T = 6,000/W2 where T is time of
exposure permitted and W is power
density in mW/cm2
. 50 mW/cm2 for periods >6 rain
18,000 mW-sec/cm2 for periods <6 min
100 kV/m peak pulse, 1 pulse/minute
Occupational Groups The Population
50 V/m . 10 V/m -
5 V/m Not Established
20 V/m .4 V/m
10 V-fm 1 V/m
5 V/m Not Established
10 Man' 1
-------
... -. .. ,- , , 29 ' . , , ,
standards in the U.S. and similar on^s in the USSR,
Cone1usi ons and Recommendati ons ,
* '",-"- -» ' f
On the basis of a theoretical analysis of possible radiation -
levels near various broadcast towers in Hawaii, there are no locations
where the OSHA standard is exceeded. The principal sources of high
intensity RF exposure are the FM radio and TV stations as opposed to _
-' . ! ' " "U
the AM radio stations. It appears that specific locations may be
subject to exposures in the 1 to 10 mW/cm2 4ange depending on the,
i '... ' ' v
particular geometry of the antenna, building, and local terrain. Power
densities-in.this range are probably limited to the immediate area
about the base of the installations in question, be it on a roof or at
ground level beneath a short tower. There may exist numerous unrestric-
).'--' ' ' . '. '' . - '.' .' - ".. ,; ;
ted areas in which individuals may experience exposures of about 1
* . .' ' k .
mW/cm2, this being 0.1 of the OSHA guide. Radiation at steep depression
' - -,*"''
angles has been recently observed at other broadcast stations (20,21)
and represents a unique aspect of the overall hazard evaluation in that
the intensity due to this steep angle radiation is not calculable with
accuracy.
The effects of building attenuation are difficult to assess
theoretically but will, in general, produce substantial reductions in
exposure. It is possible, though, that due to standing wave formation
with a glassed-in area, the inside field intensity could equal the
-- " --..>. , '-.'-
calculated values just outside the glassed area.
-------
, 30
Local field strengths from AM standard broadcast stations are
less potentially hazardous because of their much lower frequency and
lower amplitudes. The possibility of RF voltage induction in very
nearby conductors may prove undesirable from the standpoint of inter-
ference, RF shocks, or detonation of electroexplosives (22).
RF levels in the near vicinity of FM and TV stations, whether on
the roof or in adjacent buildings, are of sufficient intensity to be
a potential source of interference to critical medical devices such as
pacemakers.
The distribution of broadcast installations in Honolulu suggests
that there will not be areas where biologically hazardous (>10 mW/cm2)
field intensities could exist due to the multiple source environment.
There appears to be no frankly hazardous exposure situations
possible, but there is the possibility of certain areas where the power
density clearly could exceed 1/10 of the OSHA standard. This situation
may not be substantially different from a number of other metropolitan
areas where the boradcast source density is high and tall buildings
predominate.^ The Honolulu area may represent a somewhat unusual
exposure situation in that there exist several high power FM stations
on buildings near which adjacent buildings are approximately the same
height. Generally in broadcast installations on tall buildings, the
ERP is limited to minimize the potential for interference to distant
FM stations using the same frequency.
-------
31 ' .. '' : ';' :
The validity of .the.calculational approach used in this report
needs to be evaluated by making field measurements at the base of VHP
TV and FM towers and comparing these measurements with theoretical
results. Such a field measurement program is being conducted by EPA.
In conjunction with ambient, broad frequency range, electromagnetic
radiation exposure level measurements using a specially developed
monitoring van, measurements on roof tops and at tower bases in major
metropolitan areas on a specific source basis has been initiated.
Limited EPA measurement data has verified the unexpected high intensity
steep angle beam from some FM stations, but these measured values do
not exceed worst case calculated values. Until the measurements are
completed it must be assumed that the steep angle radiation phenomena
from some FM broadcast stations may also be characteristic of VHF TV
antennas.
; , In summary, based on the data provided and conservative assumptions,
none of the calculated values exceeds TO mW/cmz, the OSHA standard for
' ' -/ \
occupational exposure. There are several locations where there is a
possibility for exposure in the 1 to 10 rnW/cm2 range. The population
subject to exposure levels in this range is not well defined but is
probably very small. While these levels are of interest because they
are within a factor of 10 of the occupational standard and need to be
documented for future standard considerations, we would not recommend
. '.;-.-. ' - . ' ' . * ' :.'/.
that any action be taken at the present time. The model used to
calculate the exposure levels at steep depression angles in the .
-------
32
immediate vicinity of FM and VHP television antennas needs additional
investigation through actual measurements. This model investigation
is incorporated into current field study plans and we have uncovered
nothing unique about the antennas or their siting that would dictate
that the planned measurements should be done in Hawaii as opposed to
some other more convenient site.
-------
33
References
1. Pellegrin, D. Are radio-TV towers a peril to neighbors? Article
in Honolulu Advertiser, January 15, 1975.
2. Radio Tower Sparks a Complaint. Article in'Honolulu Advertiser,
July 31y 1968.
3. Mayer, P. Radio tower 'sparks' dispute with Matson. Article in
Honolulu Star-Bulletin, July 30, 1968.
!''"''"
4. Requesting a study of possible harmful radiation effects from
broadcast towers. Senate concurrent resolution, SCR No. 62,'S.D..
1,-H.D. 1, Eighth Legislature, State of Hawaii, 1975.
5. Tell, R.A. Broadcast radiation: how safe is safe? IEEE Spectrum,
Vol. 9, No. 8, August 1972, pp. 43-51.
6.
Broadcasting 1974 Yearbook. Broadcasting Publications, Inc.,
Washington, DC, 1974.
7. FCC list of FM broadcast stations. This listing is not routinely
available to the public.
8. FCC list of TV broadcast stations. This listing is not routinely
available to the public.
-'" . . ' ' \ '
9. Television Factbook. 1974-1975 Edition/No. 44,.Television Digest,
Inc., Washington, DC, 1974.
10. Official list ,of notified assignments of standard broadcast, stations
of the United States of America. Published by the FCC, December 26,.
1973 with updates.
11. Athey, T.W., R.A.' Tell, and D.E. Janes. The use of an automated
population, data base in population exposure calculations. In
Proceedings of the Eighth Midyear Topical Symposium of the" Health
Physics Society, October 1974, pp. 29-36.
i ' .
12. Berry, L.A. and M.E. Chrisman. A Fortran program for calculation
of ground wave propagation over homogeneous spherical earth for
dipole antennas. NBS technical report 9178, March 1966.
13. Damelin, J. VHF-UHF radiation hazards and safety guidelines.
{Report No. 7104, Federal Communications Commission, Office of the
Chief Engineer, Research Division, Washington, DC 20554, July 19,
1971.
-------
34
14. FM antenna technical note 1.1. Electronics Research, Inc., date
unknown.
15. Department of Labor, Occupational Safety and Health Administration,
Section 1910.97, Federal Register: 36: 105 (May 29, 1971), nonionizing
radiation effective August 27, 1971.
16. Regulations for the administration and enforcement of the radiation
control for health and safety act of 1968. DHEW publication (FDA)
73-8015, BRH/OBD 73-5, November 1972.
17. Personal communication with Joel Thie.l, Texas State Department of
Health Resources, Radiation Control Program.
18. D'Cunha, G.F., T. Nicoud, A.M. Pemberton, F.F. Rosenbaum, and J.T.
Botticelli. Syncopal attacks arising from erratic demand pace-
maker function in the vicinity of a television transmitter.
American Journal of Cardiology, Vol. 31, pp. 789-791 , June 1973.
19. Vreeland; R.W., M.D, Sheperd, J.C. Hutchinsori. The effects of FM
and TV broadcast stations upon cardiac pacemakers. In IEEE Electro-
magnetic Compatibility Symposium Record* July 16, 17, 18, 1974
IEEE publication 740H0803-7 EMC, pp. 99-106. ,
,
20. Safety level of electromagnetic radiation with respect to personnel
at one shell plaza at Houston, TeXasv Engineering Report by Sill iman,
Moffetj and Kowal ski, Consul ting Radio Engineers, Washington, DC,
May 21, 1975.
'''.' , " : '' :-..' -~ ' , .'" ' . . "
21 . Report to the National Association of Broadcasters on the measure-
ment of power density relative to OSHA radiation hazard standards.
Prepared by Smith and Pbwstenko, Broadcasting and Telecommunications
Consultants, Washington, DC, March 1975.
22. Safety guide for the prevention of radio frequency radiation hazards
in the use of electric blasting caps. Institute of Makers of
Explosives Safety Library, Publication No. 20, New York, NY, March
1971. ... .' . ;.....:: ..... ..:.'. ...
-------
35
Appendix
VOLTAGE AND POWER RATIOS TO dB
f ATlO
1,-VOO
.94(10
.9*J7:
o*>
.99S4
.994,'!
.9931
9970
..970fl
9897
.98*6
.I'll
. "fyf. 1
.95V)
.9441
.9331
,9774
.'9170
.90IA
.6713
,!"HO
.8710
.8410
.8511
.8414 .
.8318
.B77?
.em
.8035
.7943
.785?
'.7767
.7674
.7584
.7499
.7413
.7378
.77*4 .
.7141
.7079
.69-»8
.6918
.6939
.6761
..4483
.4407
.6531
.6457
.6383
.4310
.4737
.6I6A
.4091
.6074
.5871
. 17 --4
. 5AB9
.5673
. 5559
" M9S
.5413
.*370
,5307
.»«
.5188
POWfK
R/1IO
1 0000
.9777
7954
.9731
.9908
.996*
..9843.
9ft<0
9817
9775
.7777
.T,y)
.9133
.9170
.8913
.8710
.Bill
. . .fllifl
' BI7B
.77*3
.776?
.7184
.7413
.7744
.7079
.6918
.6761
.4407
.6457
.6310
. .6144
.6036
.5886
. .5754
. 5433
.5495
.5370
; .5748
,5179
.5013
.4898
.4786.
.4477
.4571
.4447
.4345
.4766
.4147
.4074
;398I
.3R90
.3*0?
.3715
.3431
.3548
.3388
.3311
.3736
.314?
.3090
.J070
.7951
.7884
.2818
.3754
, .7693
d«
0.00
0.01
0.0?
0.03
0.04
0.05
0.04
0.07
0.08
0.09
0.1
0.3
0'.3
0.4
0.5,
^0.6
0.7
0.8
0.9
1 .0
1.1
t.7
1.3
1 .4
1.5
1.4
1 .7
IB
1.9
7.0
. 7.1
3.3
3.3
7.4
7.5
7.4
7.7
'7.8
.3.7
3.0
3.1
3.3
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
t.2
4.3
4.4
4.5
4.7
4.8
'4.9
5.0
5.1
5.?:
5.3
5.4
5.5
5.4
i.?
VOl AGl
IA O
0000
OOi?
0033
0035
0044
00 SB
0-V.9
OW
0093
0104
0'3
073
035
047
057
073
.084
.096
109
13?
.135
.148
161 '
175
.187
.307
.716
.330
.745
- .759
.774
.388
.303
.318
.334
.349
.365
.380
.396
413
.479
,445
.443
.479
.494
.514
'. Ul
.549
.547
.585
.603
.4??
.441
.440
.479
.718
.738
.758
.778
.797
.»»
.841
.863
.884
.905
.778
PQWEt
(Uno
i.rooo
1 .0073
1.0046
1 .0069.
1 .0093
1.0116
1 .fii39
I ,016?
1 ft (6
1 .0709
1 .073
1 .047
1.077
1 .094
1.177
1.148
1. 175
1.707
1 ,730
1.759
1.J8I
1.318
1 . .149
1.380
1.413
1.445
1 .479
1 . 51 4
1 ,549
1.583
1.433
I iS40
1.490
1 .738
1 ,778
1.870"
.1.842
1.905
1 .950
1.975
7.04?
3.089
3.138
3.188
3 739
7.791
7.344
7.379
7.455
7,513
3.570
J.&30
3.47?
2.754
3.818
.2. 8fl4
2.751
3.070
3.090
3 142
3.734
3.311
3. 388
3.447
3. '548
x 3.631
3.7IS
vOLTAGt
II A 1 tO
.5177
.5070
.5011
.4755
.4878
.4843
.4784
.4732
.4477
.4474
.4571
.4517
.4467
.4416
.4365
.4315
.4746
.421
.416
41?
.407
.407
.378
.3934
.3890
.3844
.3807
.3758
.3715
.3473
.3631
.3587
.3548
.3508
.3447
.3478
.3388
.3350
.3311
.3373
.3334
.3199
.3142
.7985
.7818
.7441
.751? , ,
.3371
.3339
.7113 '
. 995
. 8S4
. 778
. 585 .
. 413
759
'. 132
, 000
.03162
-.01 .
.003167
.001
.0003162
.0001
.00003162
10"'
POWER
.7630
.7570
.7517
.7455
.7397
.734*
.7791
.7737
.7188
.7138
.3089
:?04!
.199S
.1950
.1905
.1867
.1870
.1778
.1738
.1498
.1440
.163?
.1585
.1349
.1514
.1479
.1445
.1413
.1380
1 .1349
.1318
.1288
.1757
.1750
.120?
.IUS
, .1148
.1172
.1094
.107?
.1047
,1033
.1000
.08713
.07943
.07077
.04310
.05473
.OSOI?
.04447
.03981
.03548
.0316?
. .0751?
.01775
01 5B5
.01359
.01000
.00100
.00010
. .00001
15-'
io-'
10-'
10'*
io-"
A
5.B
5.9
6.0
6.1
6.3
6.3J
4.4
6.5
4.6
6.7
6.B
4.9
7.0
7.1
7.7
7.3
' 7.4
7.5
7.4
7.7
7.8
7.9
8.0
8.1
8.7
8.3
8.4
8.5
8.6
8.7
8.8
8.9
7.0
9.1
9.7
7.3
9:4
9.5
7.4
9.7
7.8
9.9
10.0
io:5
11.0
11.5
13.0
13.5
13.0
13.5
14.0
14.3
IS.O
14.0
17.0
18 0
19.0
70.0
30.0
40.6
50.0
40.0.
70.0
80.0
90.0.
(00.0.
von AC i
tATIO
1.950
1.97?
1.995
7.018
3.047
3.065
7.089
3.113
3.138
3.143
3.1B8
7.313
3.739
3.745
7-391
7.317
3.344
3.371
7:399
7.477
3.45S
2.483
3.51?
2.541
2.570
2.600
2.630
3.441
2.67?
3.733
3.754
3.784
. 7.818
2.851
2.884
- 3.917-
2.951
2.985
3.030
3.055
3.090
3.174
3.167
3.350
3.548
3.758
3.981
4.717
4.447
4.73?
5.01?
5.307
5.673
4.310
7.079
7 943
. 8.913
10,000
31.670
ioo.oQ
3 il A. 70
(,000.00
3,167.00
10,000.00
31,670.00
. 10'
POWIS
RATIO
3.807
3.890
3.931
4.074
4,149
4.344
4.345
4.447
4. 171
4.677
4.784
4 .SOB
5.0i;
5. 179
5.348
5.370
5.495
5.473
5.754
5.888
4.074
6.144
4.310
6.457
6.607
v 6.761
6.918
7.079
7.244
7.413
7, 584
7.742
-7.943
8-178
8.318
8 , 51 1
B.710
8.913
9.120
9.333
7.550
9.772
10.000
11.73
17,59
14.13
15.85
- 17.78
19.95
77.37
35.1?
7B. 18
31.63
' 39.81
50.13
63 10
79 .'43
100.00
1,000 00
10,000.00
IO1
10*
10'
10'
10'
to"
------- |