MFJ Box Fan -1780 Instruction Manual
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MFJ Box Fan -1780 Instruction Manual

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MFJ-1780 Box Fan    Loop Antenna
Instruction Manual
WARNINGS ................................................................................................................... 2
THEORY OF OPERATION........................................................................................... 3
PATTERNS, POLARIZATION AND LOCATION....................................................... 3
NULLLING UNWANTED SIGNALS:.......................................................................... 4
Vertical Polarization: ...................................................................................................... 4
Horizontal Polarization: .................................................................................................. 5
OUTDOOR USE............................................................................................................. 5
INDOOR USE................................................................................................................. 6
CONTROLLER BOX INSTALLATION ....................................................................... 7
CONTROLLER BOX OPERATION ............................................................................. 7
TESTING AND OPERATION....................................................................................... 9
GENERAL OPERATION AND TROUBLESHOOTING ............................................. 11
TROUBLE SHOOTING ................................................................................................. 12
TECHNICAL ASSISTANCE ......................................................................................... 13
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Summary of Contents for MFJ Box Fan MFJ-1780

  • Page 1: Table Of Contents

    MFJ-1780 Box Fan    Loop Antenna Instruction Manual MFJ-1780 Box Fan    Portable loop Antenna WARNINGS ........................2 THEORY OF OPERATION................... 3 PATTERNS, POLARIZATION AND LOCATION............3 NULLLING UNWANTED SIGNALS:................4 Vertical Polarization: ...................... 4 Horizontal Polarization: ....................5 OUTDOOR USE......................

  • Page 2: Mfj-1780 Box Fan    Portable Loop Antenna

    The MFJ Box Fan Loop is the best performing portable small space antenna available to amateurs today. This antenna has the same size and shape as a 2x2 foot box fan. It has a carrying handle and features an indoor tuning unit.

  • Page 3: Theory Of Operation

    When resistive losses in a small loop antenna are kept low, a small loop antenna will transmit nearly as well as a full size dipole. MFJ was able to make this small loop antenna radiate nearly as well as a full size dipole by paying special attention to the electrical and mechanical construction of this antenna.

  • Page 4: Nullling Unwanted Signals

    MFJ-1780 Box Fan    Loop Antenna Instruction Manual loop as a wheel, the nulls are in the same directions that the wheel's axle would run. Signals will be attenuated more than 10 dB if they arrive within 15 degrees of the axis of the loop.

  • Page 5: Horizontal Polarization

    MFJ-1780 Box Fan    Loop Antenna Instruction Manual either too far away or is not a good enough RF reflector to cancel the horizontal radiation component of the vertical loop. HORIZONTAL POLARIZATION: Horizontal mounting of the loop antenna results in...

  • Page 6: Indoor Use

    The MFJ-1780 is a portable antenna with an easy carrying handle , you can take it with you anywhere, hotel, camp sites, traveling etc.. You can place the antenna on a picnic table, wooden table or any other non-metallic convenient place;...

  • Page 7: Controller Box Installation

    The controller box of the MFJ Box Fan Loop can be installed at any position that allows easy access to the controls of the unit and the transceiver. The coax lines should be good quality 50 ohm lines and be kept reasonably short to reduce losses.
  • Page 8 The MFJ-1782 controller box requires a 9-15 VDC, ungrounded power supply. The power jack accepts a 2.1 mm coaxial plug with the center conductor positive. The MFJ-1312B power supply will supply the correct power to the controller box.. There is also an internal battery connection that uses two 9 volt batteries for portable operation.

  • Page 9: Testing And Operation

    MFJ-1780 Box Fan    Loop Antenna Instruction Manual - Always ground the controller box to the station ground buss. - Never transmit with more than 150 watts through the controller box. - Always ground the shield of the feed line to a good earth ground for lightning and RF protection.

  • Page 10: General Operation And Troubleshooting

    Note: The tuning of this antenna is very sharp due its high Q and narrow bandwidth (few KHz). Watch you meter carefully while tuning Now you have successfully tested and operated your MFJ Box Fan Loop installation. You should now be familiar enough with the controller box and its controls buttons.

  • Page 11: Tuning When You Do Not Know The Last Operating Frequency

    MFJ-1780 Box Fan    Loop Antenna Instruction Manual After you have tested the loop as described in the TESTING AND OPERATION section you are ready to learn the short-cuts necessary for easy, day to day, use of this antenna. The following section will help you learn these short-cuts, as well as locate any problems that may occur with your new antenna system.

  • Page 12: Trouble Shooting

    MFJ-1780 Box Fan    Loop Antenna Instruction Manual 1 - Adjust the transmitter to the new frequency and transmit a steady, unmodulated carrier (1-15w is ideal). 2 - Press the appropriate Fast Tune button in and observe the SWR or the reflected power meter. The LED should light while searching for the new tuning position at this frequency.

  • Page 13: Technical Assistance

    MFJ Enterprises, Inc. warrants to the original owner of this product, if manufactured by MFJ Enterprises, Inc. and purchased from an authorized dealer or directly from MFJ Enterprises, Inc. to be free from defects in material and workmanship for a period of 12 months from date of purchase provided the following terms of this...
  • Page 14 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, jacks, or cables, etc. sent to MFJ Enterprises, Inc. will be returned at the owner's expense unrepaired.

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