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Summary of Contents for MFJ MFJ-935C
- Page 1 High-Efficiency Magnetic Loop Tuner/Antenna Current Meter MFJ-935C INSTRUCTION MANUAL ©2020 300 Industrial Park Rd. Starkville, MS 39759 P: (662) 323-5869 F: (662) 323-6551...
- Page 2 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 8:00 AM - 4:30 PM CST/CDT.
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Page 3: Table Of Contents
The MFJ-935C ........ -
Page 4: Radio Frequency Hazards
MFJ-935C High-Efficiency Magnetic Loop Tuner Instruction & Technical Manual RADIO FREQUENCY HAZARDS BACKGROUND INFORMATION The following warning is printed on the back of the MFJ-935C High-Efficiency Magnetic Loop Tuner/Antenna Current Meter ™. WARNING DO NOT touch or come into contact with Loop Connectors or... -
Page 5: An Electromagnetic Plane Wave
MFJ-935C High-Efficiency Magnetic Loop Tuner Instruction & Technical Manual Figure 1: An Electromagnetic Plane Wave Electromagnetic waves travel through space at the speed of light. Wavelength and frequency are inversely related by a simple equation: frequency wavelength = the speed of light, or Since the speed of light is a fundamental constant, High Frequency (HF) electromagnetic waves have short wavelengths, and Low-Frequency (LF) waves have long wavelengths. -
Page 6: Rf Precautions
HF loops, for example, yield RF fields very near the antenna that are much higher than the standard amateur radio station outdoor antenna installation fields. Therefore, when you use the MFJ-935C High-Efficiency Magnetic Loop Tuner/Antenna Current Meter ™ in your shack, at a portable location, or in a hotel room, care must be taken to exceed established MPE to yourself and others who may encounter the RF field associated with your operation. -
Page 7: Rf Radiation Exposure Concerns
OPERATING ENVIRONMENTS & GUIDELINES Tables 1 and 2 list MFJ-935C High-Efficiency Magnetic Loop Tuner/Antenna Current Meter ™ operating environments, average power level, and safe distances that should provide compliance with the FCC’s MPE recommendations and standards for controlled and uncontrolled populations. -
Page 8: 100W Indoor And Outdoor Operating Environment
MFJ-935C High-Efficiency Magnetic Loop Tuner Instruction & Technical Manual Table 1: 100W Indoor and Outdoor Operating Environment Frequency (MHz) Controlled Population Uncontrolled Population Height (m) Exposure (ft m) Exposure (ft m) 1.18 0.36 1.68 0.51 1.25 0.38 2.48 0.75 1.88 0.57... -
Page 9: The Mfj-935C
THE MFJ-935C INTRODUCTION The MFJ-935C High-Efficiency Magnetic Loop Tuner ™ is a small, versatile, high-efficiency device that turns any wire or coax loop into a high-efficiency multi-band transmitting loop antenna system designed for 50-ohm use at 150 Watts maximum input and all modes. It consists of two primary components: •... -
Page 10: Features
The MFJ-935C High-Efficiency Magnetic Loop Tuner/Antenna Current Meter ™ has a mount for either an MFJ-57B or MFJ-58B PVC Cross assembly or your own homebrewed assembly. The assembly is inserted into the three-quarter-inch PVC receptacle mounted on the top of the unit’s... -
Page 11: Front Panel
MFJ-935C High-Efficiency Magnetic Loop Tuner Instruction & Technical Manual Figure 4: Front-panel Controls: 1.) Tuning Control, 2.) Matching Control, 3.) Meter Sensitivity, 4.) Coax Output, 5.) Antenna Current Meter, 6.) PVC Mount Figure 5: Rear-panel Connections: 1.) Wire loop connectors, 2.) Coax input This unit is not intended for outdoor installation except during portable operation and must be protected from the elements. -
Page 12: Loop Theory
Another loss component is due to current flowing in the soil via capacitance between the loop and soil surface. These are all reduced by increasing the height of the MFJ-935C above the ground as measured from the tuner box. An operational height equal to... -
Page 13: System Setup
Designing an outdoor loop for a band such as 7 MHz could be a challenge yet result in a very good radiator and especially good receiving antenna for DX-ing and rag-chewing. We at MFJ think the experimental aspects of the MFJ-935C are exciting, and can provide hours of quality operating, even at QRP levels. -
Page 14: System Operation
If the loop antenna is rigid, then place it in a position to accommodate its particular shape and size. The MFJ-57B or MFJ-58B make this simple by providing a precut PVC frame and wire lengths. - Page 15 • Once a peak is found, alternately adjust the TUNING and MATCHING controls until the peak is maximized. Step 6 Apply 10 to 20 Watts of power to the MFJ–935C and adjust the TUNING control for maximum RF current and the MATCHING control for minimum SWR on your external SWR/Wattmeter.
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Page 16: Quick-Start Instructions
S-Meter reading. The tuner will produce a peak when the exact position for the controls and switches is found. Step 5 Apply 10 to 20 Watts of power to the MFJ–935C and adjust the TUNING control for maximum RF current and the MATCHING control for minimum SWR on your external... -
Page 17: Mfj-935C Accessories
These kits are: • the MFJ-57B, which contains a PVC Cross device for mounting a precut and lugged wire loop to the top cover of the tuner. This flexible 10-gauge wire loop covers 20 and 30 meters, and the ends have low-resistance lugs. -
Page 18: Technical Assistance
MFJ Technical Service at (662) 323-0549 or the MFJ Factory at (662) 323-5869. You will be best helped if you have your unit, manual and all information on your station handy so you can answer any questions the technicians may ask. - Page 19 USER NOTES...
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