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MFJ-935C

High-Efficiency Magnetic Loop Tuner

Instruction & Technical Manual

Step 8

You can now enjoy operating in your favorite mode. However, if you change frequency

more than about 5 kHz, you may find you will need to re-adjust the TUNING controls for
minimum SWR. Rotate the TUNING control clockwise for higher frequencies and counter
clockwise for lower frequencies. Larger fequency changes can cause the MATCHING control to also
require adjustment. This concludes the MFJ–935C

High-Efficiency Magnetic Loop Tuner/Antenna

Current Meter

™

operating instructions.

5.2

QUICK-START INSTRUCTIONS

Although careful and complete reading of the technical manual is certainly important when
receiving new equipment, successful operation of MFJ-935C

High-Efficiency Magnetic Loop

Tuner/Antenna Current Meter

™

can be achieved with minimum time and effort as long as certain

and specific instructions are followed. Strict adherence to any WARNINGS and CAUTIONS
associated with personal safety, coupled with following specific procedural steps can lead to a
unique operating experience in a very short time.

WARNING

DO NOT touch or come into contact with Loop Connectors or Loop

Antenna while transmitting

YOU CAN BE SERIOUSLY INJURED

Step 1

Place the MFJ-935C

High-Efficiency Magnetic Loop Tuner/Antenna Current Meter

™

at

the chosen place of operation, and connect either the wire loop to the wing nut terminals on the
rear panel or the coax loop to the SO-239 connectors on the side.

Step 2

Setup the MFJ-935C

High-Efficiency Magnetic Loop Tuner/Antenna Current Meter

™

as

illustrated in Figure 6.

Step 3

Set the MFJ–935C controls to the following positions for the 14.2 MHz operation

(settings are approximate, but should be close):

•

TUNING control to Position 3.0.

•

MATCHING control to Position 9.0.

•

METER SENSITIVITY control to the fully clockwise position.

Step 4

Tune the transceiver or receiver to the 20 meter band and frequency of interest and

adjust the MFJ-935C

High-Efficiency Magnetic Loop Tuner/Antenna Current Meter

™

controls for

maximum noise and 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

-13-

Содержание MFJ-935C

Страница 1: ...High Efficiency Magnetic Loop Tuner Antenna Current Meter MFJ 935C INSTRUCTION MANUAL 2020 MFJ Enterprises Inc 300 Industrial Park Rd Starkville MS 39759 P 662 323 5869 F 662 323 6551 ...

Страница 2: ...onal 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 00 AM 4 30 PM CST CDT ...

Страница 3: ...TEM SETUP 10 4 1 CONFIGURATION 10 4 2 LOOP CONSTRUCTION 10 5 SYSTEM OPERATION 11 5 1 DETAILED OPERATION INSTRUCTIONS 11 5 2 QUICK START INSTRUCTIONS 13 5 3 MFJ 935C ACCESSORIES 14 6 TECHNICAL ASSISTANCE 15 List of Figures 1 An Electromagnetic Plane Wave 2 2 The Electromagnetic Spectrum 3 3 The MFJ 935C 6 4 Front Panel 8 5 Rear Panel 8 6 Typical MFJ 935C Configuration 10 List of Tables 1 100W Indoo...

Страница 4: ...o 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 or radiating through space The movement of electrical charges generates these waves For example the movement of charge in a radio station anten...

Страница 5: ... are usually characterized by their approximate corresponding wavelengths such as 12 15 17 20 meters et cetera The electromagnetic spectrum Figure 2 includes all of the various energies of electromagnetic radiation ranging from extremely low frequency ELF ranges with very long wavelengths to all the way up to x rays and γ rays which have very high frequencies and correspondingly short wavelengths ...

Страница 6: ...ines 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 Def initions 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 website at https www fcc gov general...

Страница 7: ...ers 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 1 6 OPERATING ENVIRONMENTS GUIDELINES Tables 1 and 2 list MFJ 935C High Efficiency Magnetic Loop Tuner An...

Страница 8: ...0 93 4 06 1 23 1 3 07 0 93 4 95 1 50 3 24 0 3 23 0 98 5 48 1 66 1 3 37 1 02 5 51 1 67 3 28 0 3 47 1 05 6 04 1 83 1 3 47 1 05 6 04 1 83 3 Table 2 150W Indoor and Outdoor Operating Environment Frequency MHz Controlled Population Exposure ft m Uncontrolled Population Exposure ft m Height m 7 0 1 45 0 44 2 05 0 62 1 1 52 0 46 3 00 0 91 3 10 0 2 28 0 69 3 00 0 91 1 2 77 0 84 3 66 1 11 3 14 0 2 87 0 87 ...

Страница 9: ...wo functions First it uses various lengths of wire to create a very high Q tuned circuit that is used as a transmitting loop antenna An MFJ 19 low loss Butterfly capacitor with no rotating contacts available separately for your own homebrew projects is the heart of this circuit The second function is as a matching network that matches the high Q transmitting loop circuit to your 50Ω coaxial cable ...

Страница 10: ...ics and reduces overloading Indoor Use Perfect for apartments hotel rooms antenna restricted and portable locations 2 3 CONTROLS CONNECTIONS The MFJ 935C High Efficiency Magnetic Loop Tuner Antenna Current Meter front panel controls and indicators Figure 4 function to permit resonating the wire loop at the output and matching the coaxial line impedance at the input of the tuner 1 TUNING This adjus...

Страница 11: ...ls 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 8 ...

Страница 12: ...iciency of the MFJ 935C High Efficiency Magnetic Loop Tuner Antenna Current Meter increases with its height above ground When traveling a room above the ground floor makes for a better portable operation experience with the MFJ 935C At very low heights close coupling to the ground causes detuning and losses due to the twin factors of current induced into a mirror image of the loop below the surfac...

Страница 13: ... Exact frequency coverage depends on each individual installation configuration involving choice of wire loop length loop shape height above ground and operating environment The loop can be constructed from wire tubing sheet metal or coaxial cable An especially good material is one inch wide PCB board However finding a piece of PCB board long enough to form into a circular loop for 7 175 MHz may p...

Страница 14: ...ps in a specific order Moreover you must have first consulted Section 1 of this manual to ensure compliance with established standards for MPE to certain levels of RF radiation WARNING DO NOT touch or come into contact with Loop Connectors or Loop Antenna while transmitting YOU CAN BE SERIOUSLY INJURED Step 1 Place the MFJ 935C High Efficiency Magnetic Loop Tuner Antenna Current Meter at the chose...

Страница 15: ...ound the loop length is incorrect for the frequency of interest At this point refer to Tables 3a and 3b for the most efficient loop lengths 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 exte...

Страница 16: ...g experience in a very short time WARNING DO NOT touch or come into contact with Loop Connectors or Loop Antenna while transmitting YOU CAN BE SERIOUSLY INJURED Step 1 Place the MFJ 935C High Efficiency Magnetic Loop Tuner Antenna Current Meter at the chosen place of operation and connect either the wire loop to the wing nut terminals on the rear panel or the coax loop to the SO 239 connectors on ...

Страница 17: ...ence between 50 and 100 watts is less than half of an S unit and is not noticeable on the receiving end Step 7 You can now enjoy operating in your favorite mode However if you change frequency more than about 5 kHz you may find you will need to re adjust the TUNING controls for minimum SWR Rotate the TUNING control clockwise for higher frequencies and counter clockwise for lower frequencies Even g...

Страница 18: ...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 You can also send questions by mail to MFJ Enterprises Inc 300 Industrial Park Road Starkville MS 39759 by Facsimile FAX to 662 323 6551 or by email to techinfo mfjenterprises com Send a thorough descr...

Страница 19: ...USER NOTES ...

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