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Cold & Calm
30°F
Forecast
Alerts
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Radar
Traffic
Cameras
BLM/Fire
Cameras
Cameras
Roads
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Sun
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Home Of the Elko Nevada Weather Page.
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Amateur Radio RF Safety Calculator
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This is a main beam power density estimation program intended for use as
part of a routine evaluation of RF safety compliance with FCC regulations.
Amateur Radio operators licensed by the Federal
Communications Commission of the United States of America are required
to do a "routine evaluation" of the strength of the RF fields around their
stations, subject to certain
exemptions.
These rules can be found in the FCC's ET Docket No. 93-62. More
information can be found at the ARRLWeb's
RF Safety page.
This program uses the formulas given in FCC
OET Bulletin No. 65 to estimate power density in the
main lobe of an antenna, with use of the EPA-recommended ground reflection
factor as an option. This program is intended for approximate far-field
calculations. It may overestimate the actual field strength of high-gain
antennas in the near field (within several wavelengths of the antenna.)
However, it may also underestimate the strength of fields that may be
encountered in hot spots in the near field. No computer program can
predict where wiring or reflective objects may create hot spots in your
particular installation.
This is a World Wide Web front end for a public domain program written by W4/VP9KF
using PHP.
This program was derived from a public domain
BASIC program written by
Wayne
Overbeck N6NB and published in the January, 1997 issue of
CQ VHF, p. 33. Terms: GNU Licence.
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No Warranties: This information is provided "as is" without any
warranty, condition, or representation of any kind, either express or implied,
including but not limited to, any warranty respecting non-infringement, and the
implied warranties of conditions of merchantability and fitness for a
particular purpose.
In no event shall we be liable for any direct, indirect, special, incidental, consequential
or other damages howsoever caused whether arising in contract, tort, or
otherwise, arising out of or in connection with the use or performance of
the information contained on this web site.
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Frequencies
in MHz |
Peak Envelope
Power in
Watts |
1.800 - 2.000
|
500
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3.500 - 4.000
|
500
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7.000 - 7.300
|
500
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10.100 - 10.150
|
425
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14.000 - 14.350
|
225
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18.068 - 18.168
|
125
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21.000 - 21.450
|
100
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24.890 - 24.990
|
75
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28.000 - 29.700
|
50
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50.000 - 54.000
|
50
|
144.000 - 148.000
|
50
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222.000 - 225.000
|
50
|
420.000 - 450.000
|
70
|
902.000 - 928.000
|
150
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1240.000 - 1300.000
|
200
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2300.000 and higher
|
250
|
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Exemptions
to Routine RF Radiation Evaluations
On 1997-08-27, in the
Second Memorandum and Order, the FCC adopted a sliding scale for
categorical exemption to routine RF radiation compliance testing based on peak
envelope power (PEP) at various Amateur Radio operating frequencies. While the
RF radiation exposure compliance levels are based on
average power, the categorical exemptions from the
requirement for periodic station compliance testing are based upon peak
envelope power (PEP). Stations operating at or below these respective PEP
levels are categorically excluded from having to perform a routine RF
radiation evaluation. However, all stations, regardless of
power level, still must comply with the RF exposure limits.
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Average Power Estimate
Amateurs are required to perform a routine evaluation of the strength of
the RF fields around their stations, subject to certain exemptions based on
peak envelope power (PEP) levels at the various amateur bands. However,
the FCC regulations on permissible RF exposure are not based on peak envelope
power (PEP), but on average power over a 30-minute time period for
uncontrolled environments, or a 6-minute time period for controlled
environments. The part of the regulations that determine whether a station
operator must perform a periodic evaluation, however, is based on PEP.
Operating Mode |
Duty Factor |
Morse code (CW)
|
40%
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SSB phone
|
20%
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FM
|
100%
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RTTY/Digital
|
100%
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AM
|
100%
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To estimate your average power, first start with your Peak Envelope Power
(PEP). Multiply that by the duty factor for the mode you
are using, then by the maximum percentage of time you expect to operate within
the averaging period.
For example, if you operate a 1500 watt PEP SSB phone station that is on
for 10 minutes, off for 10 minutes and on for 10 minutes, you are operating
with 200 watts average power (1500 watts PEP * 20% * 67% = 200 watts average
power) over a 30 minute period. If you operate a 1500 watt Morse Code (CW)
station over the same time period, you have 1500 watts PEP * 40% * 67%, or
400 watts average power.
In most cases for the 6-minute controlled environment
exposure estimate, you should probably assume that it is possible to operate
over the entire 6-minute period, so the 1500 watt PEP SSB phone station would
be 300 watts average power for controlled-exposure calculations. An RTTY or
digital bulletin station, or FM repeater transmitter, would probably be on for
the full 30 minute time period, so the RTTY bulletin station or FM repeater
would be 1500 watts average power. If it operated 10 minutes on, 10 minutes
off and 10 minutes on, it would have 1000 watts average power over 30 minutes.
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Ham Radio
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