Information in this manual is designed for user purposes only and is not
intended to supersede information contained in customer regulations, technical
manuals/documents, positional handbooks, or other official publications. The
copy of this manual provided to the customer will not be updated to reflect
current data.
Customers using this manual should report errors or omissions,
recommendations for improvements, or other comments to MFJ Enterprises, 300
Industrial Park Road, Starkville, MS 39759. Phone: (662) 323-5869; FAX: (662)
323-6551. Business hours: M-F 8-4:30 CST.
The following WARNING is labeled on the MFJ-933 LOOP TUNERTM Rear
Panel:
TM
Instruction & Technical Manual
RF HAZARD PRECAUTIONS
WARNING
DO NOT touch or come into contact with Loop
Connectors or Loop Antenna while transmitting
YOU CAN BE SERIOUSLY INJURED
Using the MFJ-933 Loop Tuner
voltages and HIGH CURRENTS during normal operation. The Hi-Q circuit
produced by resonating the wire loop connected to the tuner, and matching it to
the 50-Ohm coax supplying power creates this unique operating environment.
TM
can, and in fact does, produce LETHAL
!!!
NOTICE
It is imperative that the operator specifically follows operating instructions and
complies with all CAUTIONS, WARNINGS, and FCC Guidelinesfor Human
Exposure to Radio frequency (RF) Electromagnetic Fields
Radio frequency (RF) Radiation
Radio frequency (RF) energy is one type of electromagnetic energy.
Electromagnetic waves and associated phenomena can be discussed in terms of
energy, radiation or fields. Electromagnetic "radiation" is defined as waves of
electric and magnetic energy moving together (i.e., radiating) through space.
The movement of electrical charges generates these waves. For example, the
movement of charge in a radio station antenna (the alternating current) creates
electromagnetic waves radiating away from the antenna and intercepted by
receiving antennas. Electromagnetic "field" refers to the electric and magnetic
environment existing at some location due to a radiating source such as an
antenna.
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MFJ-933 Loop Tuner
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Instruction & Technical Manual
RF HAZARD PRECAUTIONS
An electromagnetic wave is characterized by its wavelength and frequency. The
wavelength is the distance covered by one complete wave cycle. The frequency
is the number of waves passing a point in a second. For example, a typical radio
wave transmitted by a 2-meter VHF station has a wavelength of about 2 meters
and a frequency of about 145 million cycles per second (145 million Hertz): one
cycle/second = one Hertz, abbreviated Hz.
Electromagnetic waves travel through space at the speed of light. Wavelength
and frequency are inversely related by a simple equation: (frequency) times
(wavelength) = the speed of light. Since the speed of light is a constant quantity,
High Frequency (HF) electromagnetic waves have short wavelengths, and LowFrequency (LF) waves have long wavelengths. Frequency bands used for
amateur radio transmissions are usually characterized by their approximate
corresponding wavelengths, e.g., 12, 15, 17, 20 meters, etc.
The electromagnetic "spectrum" includes all of the various forms of
electromagnetic energy ranging from extremely low frequency (ELF) energy (with
very long wavelengths) to all the way up to X-rays and gamma rays, which have
very high frequencies and correspondingly short wavelengths. In between these
extremes lie radio waves, microwaves, infrared radiation, visible light and
ultraviolet radiation, respectively. The RF part of the electromagnetic spectrum
can generally be defined as that part of the spectrum where electromagnetic
waves have frequencies that range from about 3 kilohertz (kHz) to 300 gigahertz
(GHz). Figure 1 illustrates the electromagnetic spectrum.
Figure 1 The Electromagnetic Spectrum
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MFJ-933 Loop Tuner
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Instruction & Technical Manual
RF HAZARD PRECAUTIONS
FCC OET Bulletin 65, Supplement B, Evaluating Compliance with FCC
Guidelines for Human Exposure to Radio frequency Electromagnetic
Fields.
The FCC Office of Engineering Technology (OET) Bulletin 65, Supplement B,
Evaluating Compliance with FCC Guidelines for Human Exposure to Radio
frequency Electromagnetic Fields impacts directly the use and operation of the
MFJ-933 Loop Tuner
TM
. It establishes safe operating distances from the loop
antenna and associated power levels in order to permit the operator and persons
that may be impacted by operation to exist in a safe, RF radiation hazard-free
environment. Guidelines for Maximum Permissible Exposure (MPE) are defined
in Supplement B of the bulletin.
IMPORTANT NOTE
Use Supplement B in connection with FCC OET Bulletin 65,
Version 97-01. The information in the supplement provides
additional detailed information used for evaluating compliance of
amateur radio stations with FCC guidelines for exposure to radio
frequency electromagnetic fields. However, Supplement B users
should also consult Bulletin 65 for complete information on FCC
policies, guidelines and compliance-related issues. Definitions of
terms used in this supplement appear in Bulletin 65. Bulletin 65
can be viewed and downloaded from the FCC’s Office of
Engineering and Technology’s World Wide Web Internet Site:
http://www.fcc.gov/oet/rfsafety
OPERATING ENVIRONMENTS
Under some circumstances, such as an antenna located unusually near humans,
an indoor antenna in a living space, or a balcony-mounted antenna a foot or so
away from a neighbor’s balcony, the FCC could require a station evaluation or
take other action. Computer models of small HF loops, for example, yield RF
fields very near the antenna that are much higher than the standard amateur
radio station outdoor antenna installation yields. Therefore, when you use the
MFJ-933 Loop Tuner
one such as a hotel/motel room care must be taken not to exceed established
MPE to yourself and others who may encounter the RF field associated with your
operation.
TM
in your Ham Shack, at a portable location (outdoors), or
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MFJ-933 Loop Tuner
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Instruction & Technical Manual
RF HAZARD PRECAUTIONS
RF RADIATION EXPOSURE CONCERNS
Controlled population exposure limits apply to amateur licensees and members
of their immediate household (but not their neighbors - see next paragraph). In
general, a controlled environment is one for which access is controlled or
restricted.
In the case of a fixed or portable amateur station, the licensee or grantee is the
person responsible for controlling access and providing the necessary
information and training as described in FCC OET Bulletin 65, Supplement B.
General population/uncontrolled exposure limits apply to situations in which the
general public may be exposed, or in which persons who are exposed as a
consequence of their employment, such as hotel/motel employees or overnight
residents, may not be made fully aware of the potential for exposure or cannot
exercise control over their exposure. Therefore, members of the general public
always fall under this category when exposure is not employment-related, as in
the case of residents in an area near a broadcast tower. Neighbors of amateurs
and other non-household members would normally be subject to the general
population/uncontrolled exposure limits.
OPERATING ENVIRONMENTS & GUIDELINES
Table 1 and Table 2 lists MFJ-933 Loop Tuner
TM
operating environments,
average power level, and safe distances that should provide compliance with the
FCC’s MPE recommendations/standards for controlled and uncontrolled
populations. Distance data listed is a result of computer-modeling a circular loop,
which is the most efficient radiator configuration. Parameters used include those
listed below:
• Loop perimeter or circumference (75% of a quarter wave loop in length for
each band)