Quantcast Field Intensity Measurements

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Hero Unsafe. HERO UNSAFE ordnance materials are the most
susceptible to RF radiation and constitute the "worst-case" situation for
shore communication transmitters. An ordnance item is defined as HERO UNSAFE
when any of the following conditions exist:
(a) When its internal wiring is physically exposed.
(b) When additional electrical connections are required for the
item being tested.
(c) When EED's with exposed wire leads are handled or loaded.
(d) When the item is being assembled or disassembled.
(e) When the item remains disassembled.
Exemption.  Ordinance items may be exempted from the HERO UNSAFE
classification as the result of previous HERO tests or analyses which are
recorded for specific equipment in the NAVSEA/NAVAIR directive.
Field Intensity Measurements. Measurements of field intensity will
ascertain the magnitude of an electromagnetic field.  The field intensity of
electromagnetic fields at communication frequencies (100 kHz to 1000 MHz) is
referred to in terms of vertical electric field strength in units of volts per
meter.  A chart in NAVSEA OP3565/NAVAIR 16-1-529/NAVELEX 0967-LP-624-6010
indicates that, for HERO UNSAFE ordnance, the maximum safe field intensity is
0.2 V/m throughout the 2 to 32 MHz frequency range. This criterion could
become a stringent restriction for radiation from communication transmitters
of reasonably high power.
Hero Safe. HERO SAFE ordnance systems are not susceptible to
radiation under any condition.
Hero Susceptible. Many ordnance systems are classified as HERO
SUSCEPTIBLE under most conditions.  The maximum safe field intensity
prescribed for HERO SUSCEPTIBLE ordnance is 2.0 V/m from approximately 3.7 to
10.1 MHz frequency range.
Safe Distances.  Since the maximum safe field intensity varies
widely for the three classifications of ordnance, it is important to ascertain
whether ordnance systems will be handled or stored in the vicinity of a
transmitter site. Refer to NAVSEA OP3565/NAVAIR-16-1-529/ NAVELEX 0967-LP-
624-6010 for safe distances from specific antennas.
If so, the classification of the ordnance most sensitive to RF radiation will
determine the maximum field strength that can be tolerated.
Fuel Hazards.  General guidance to prevent hazards to fueling in an
RF environment are provided in NAVSEA OP3565/NAVAIR 16-1-529/NAVELEX 0967-LP-
624-6010 Volume 1 and is as follows:  Transmitters with 250 watts radiated
output or less should not be installed within 50 feet (15 m) of fuel-handling
or fueling areas.  Transmitters with over 250 watts radiated output should not
be installed within 200 feet (61 m) of fuel-handling or fueling areas.  In no


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