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MFJ-9234 Mini Loop Tuner 

 

 

Instruction & Technical Manual 

 

- 8 - 

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. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Summary of Contents for MFJ-9234

Page 1: ...Read All Instructions Before Operating Equipment MFJ ENTERPRISES INC 300 Industrial Park Road Starkville MS 39759 USA Tel 662 323 5869 Fax 662 323 6551 COPYRIGHT 2016 MFJ ENTERPRISES INC Model MFJ 9234 VERSION 1A Mini Loop Tuner ...

Page 2: ...hnical 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 ...

Page 3: ...iciency device that turns any wire loop into a high efficiency multi band transmitting antenna system Designed to mount directly to your radio it is perfect for on the go operation It is designed for 50 ohm use at QRP power input on all modes Two items are required MFJ 9234 Mini Loop Tuner TM Shown in Figure 1 Wire Loop s 55 ft of wire included Figure 1 MFJ 9234 Mini Loop Tuner ...

Page 4: ... 9234 Mini Loop Tuner TM uses fixed wire lengths to cover roughly a 1 5 1 frequency ratio 28 18 MHz 10 7 MHz etc Exact frequency coverage depends on each individual installation and involves your choice of wire length loop diameter loop shape height above ground level plus other stray factors in the immediate operating environment MFJ 9234 MINI LOOP TUNERTM FEATURES Passive Network No power supply...

Page 5: ...power limitation 25W RF burns can be exceptionally painful and slow to heal EXCESSIVE RF EXPOSURE NOTICE You must follow all PRECAUTIONS WARNINGS and FCC Guidelines for Human Exposure to Radio frequency RF Electromagnetic Fields What Is Radio Frequency RF Radiation Radio frequency RF energy is one form of electromagnetic energy Electromagnetic waves and associated phenomena can be discussed in ter...

Page 6: ...y HF electromagnetic waves have short wavelengths and Low Frequency 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 l...

Page 7: ...r 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...

Page 8: ...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 expos...

Page 9: ...cordingly When traveling a room at some elevation above ground level makes for a better portable operation experience At very low heights close coupling to the ground causes detuning and losses due to current induced into a mirror image of the loop below the surface with resistance of the image loop proportional to soil resistance Another loss component is caused by current flowing in the soil via...

Page 10: ...er or transceiver 5 Watts minimum with built in SWR Wattmeter MFJ 9234 Mini Loop Tuner TM Coaxial cable s Wire cut to approximately 75 of a wavelength at the chosen resonant frequency Figure 3 is a block diagram of the typical MFJ 9234 Mini Loop Tuner TM setup configuration Figure 3 Typical MFJ 9234 Mini Loop Tuner TM Configuration Transmitter Transceiver With SWR Wattmeter Matching Network Loop M...

Page 11: ...8 53 30 M 20 0 6 96 20 M 13 0 3 96 17 M 9 0 2 75 15 M 7 0 2 13 12 M 5 5 1 68 10 M 4 0 1 22 MFJ 9234 Multi Band Loop Wire Lengths Bands Length feet Length meters 40 30 M 20 0 6 96 30 20 M 13 0 3 96 30 20 17 M 9 0 2 75 20 15 M 7 0 2 13 17 15 10 M 4 0 1 22 The applications and parameters can be adjusted easily with the help of the Freeware programs previously mentioned and you may choose to design a ...

Page 12: ...compliance with established standards for Minimum Permissible Exposure 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 9234 Mini Loop Tuner TM at the chosen place of operation typically directly to the back of your radio and connect the loop antenna to the bindi...

Page 13: ...iver or receiver to the band and frequency of interest and Ear ball tune the MFJ 9234 Mini Loop Tuner controls for maximum noise and S Meter reading Ear balling like Ball parking is a term often used to describe the listening process as used to hear a peak in reception before actually applying a transmit signal to the tuner The tuner will produce a peak when the proper positions for the controls a...

Page 14: ...d Step 6 Apply no more than 5 10 Watts of power to the MFJ 9234 Mini Loop Tuner and adjust the TUNING and MATCHING controls for minimum SWR on your external WR Wattmeter Readjust the controls until you see no further improvement in minimum SWR Then apply more power if required to maintain communication do not exceed 25 Watts Step 7 Be sure that MPE distance standard as defined in Supplement B of t...

Page 15: ...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 complete descr...

Page 16: ...s available by calling the Service Department at 662 323 0549 or the MFJ Factory at 662 323 5869 4 This warranty does not apply to kits sold by or manufactured by MFJ Enterprises Inc 5 Wired and tested PC board products are covered by this warranty provided only the wired and tested PC board product is returned Wired and tested PC boards installed in the owner s cabinet or connected to switches ja...

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