MFJ MFJ-935B User Manual

DISCLAIMER

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.

MFJ-935B Loop Tuner

Instruction & Technical Manual

TABLE OF CONTENTS

TOPIC

PAGE

TABLE OF CONTENTS ii

LIST OF FIGURES ii

LIST OF TABLES ii

RF HAZARD PRECAUTIONS 1

INTRODUCTION & SYSTEM FEATURES 7

SYSTEM DESCRIPTION 10

LOOP THEORY 12

SYSTEM SETUP 14

LOOP CONSTRUCTION 15

SYSTEM OPERATION 17

FAST START INSTRUCTIONS 20

TECHNICAL ASSISTANCE 23

LIST OF FIGURES

Figure 1 The Electromagnetic Spectrum 2

Figure 2 MFJ-935B Loop Tuner

Figure 3 MFJ-935B Loop Tuner

Figure 4 MFJ-935B Loop Tuner

Figure 5 MFJ-935B Loop Tuner

Figure 6 Typical MFJ-935B Loop Tuner

w/ MFJ-57B PVC Cross Loop Kit Installed 9

Front Panel Controls & Indicators 10

Rear Panel Connectors 11

Setup Configuration 14

LIST OF TABLES

Table 1 Indoor & Outdoor Operating Environments at 100 Watts 5

Table 2 Indoor & Outdoor Operating Environments at 150 Watts 6

Table 3 MFJ-935B Most Efficient Single-band Loop Lengths 15

Table 4 MFJ-935B Convenient Multi-band Loop Lengths 15

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MFJ-935B Loop Tuner

RF HAZARD BACKGROUND INFORMATION

The following WARNING is labeled on the MFJ-935B LOOP TUNERTM Rear Panel:

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-935B 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.

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 Guidelines for 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-935B Loop Tuner

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-935B Loop Tuner

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-935B Loop Tuner

. 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-935B 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.

in your Ham Shack, at a portable location (outdoors), or

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MFJ-935B Loop Tuner

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-935B Loop Tuner

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)

• Diameter of loop conductor (approximately 4mm/10 gauge)

• Height of lowest section of loop above ground (1 and 3 meters feed-point

heights)

• Operating frequencies (7.175, 10.1, 14.2, 18.1, 21.2, 24.95, & 28.5 MHz)

• Output power in watts (100 Watts average for Table 1 and 150 Watts

average for Table 2)

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MFJ-935B Loop Tuner

Table 1 Indoor & Outdoor Operating Environments at 100 Watts

Instruction & Technical Manual

RF HAZARD PRECAUTIONS

Freq

(MHz)

7.0

Controlled Population

Exposure

(Distance in feet/meters)

1.2 0.36 2.0 0.51 100

Uncontrolled Population

Exposure

(Distance in feet/meters)

Output

Power

(Watts)

7.02 1.2 0.38 2.1 0.75 100

10.01 1.9 0.57 3. 0 0.75 100

10.02 2.3 0.69 3.6 0.92 100

14.01 2.4 0.72 3.8 0.96 100

14.02 2.5 0.77 4.6 0.96 100

18.01 2.8 0.85 5.1 1.06 100

18.02 2.9 0.87 5.2 1.08 100

21.01 3.0 0.92 5.9 1.23 100

21.02 3.1 0.93 6.0 1.50 100

24.01 3.2 0.98 6.6 1.66 100

24.02 3.3 1.02 6.6 1.67 100

28.01 3.4 1.05 7.2 1.83 100

28.02 3.4 1.05 7.3 1.83 100

MFJ-935B Loop Tuner

located at one meter in height above ground level.

MFJ-935B Loop Tuner

located at three meters in height above ground level.

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MFJ-935B Loop Tuner

Table 2 Indoor & Outdoor Operating Environments at 150 Watts

Instruction & Technical Manual

RF HAZARD PRECAUTIONS

Freq

(MHz)

7.0

Controlled Population

Exposure

(Distance in feet/meters)

1.4 0.44 2.0 0.62 150

Uncontrolled Population

Exposure

(Distance in feet/meters)

Output

Power

(Watts)

7.02 1.5 0.46 2.1 0.91 150

10.01 2.3 0.69 3. 0 0.91 150

10.02 2.7 0.84 3.6 1.11 150

14.01 2.8 0.87 3.8 1.16 150

14.02 3.0 0.93 4.6 1.40 150

18.01 3.4 1.03 5.1 1.56 150

18.02 3.4 1.05 5.2 1.59 150

21.01 3.7 1.12 5.9 1.80 150

21.02 3.7 1.13 6.0 1.82 150

24.01 3.9 1.19 6.6 2.01 150

24.02 4.1 1.24 6.6 2.02 150

28.01 4.2 1.27 7.2 2.22 150

28.02 4.2 1.27 7.3 2.22 150

MFJ-935B Loop Tuner

located at one meter in height above ground level.

MFJ-935B Loop Tuner

located at three meters in height above ground level.

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