MFJ -928 Instruction Manual
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MFJ -928 Instruction Manual

Automatic antenna tuner
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Compact IntelliTuner
TM
Automatic Antenna Tuner
Model MFJ-928
INSTRUCTION MANUAL
CAUTION: 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
5
VERSION 0A
C
COPYRIGHT
200
MFJ ENTERPRISES, INC.

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  • Page 1 Compact IntelliTuner Automatic Antenna Tuner Model MFJ-928 INSTRUCTION MANUAL CAUTION: 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 VERSION 0A COPYRIGHT MFJ ENTERPRISES, INC.

  • Page 3: Table Of Contents

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Contents THE BASICS Introduction............................1 Features............................2 Specifications........................... 2 Fast Start ............................3 Front Panel............................4 SWR LED ........................... 4 TUNE LED ......................... 4 TUNE Button........................4 Automatic/Semi-Automatic Tuning Mode ............4 ANT Button ........................
  • Page 4 Figure 1. Installation Block Diagram....................3 Figure 2. MFJ-928 Front Panel....................... 4 Figure 3. Button Action ........................5 Figure 4. MFJ-928 Back Panel ....................... 6 Figure 5. Rado Interface Connector....................6 Figure 6. Alinco Interface Cable..................... 7 Figure 7. Icom Interface Cable ....................... 8 Figure 8.

  • Page 5: The Basics

    When you key your transmitter, MFJ’s InstantRecall checks its memory to see if you have operated that frequency before. If so, tuning is instantaneous and you’re ready to operate. If not, MFJ’s algorithm (based on MFJ’s famous SWR Analyzer technology) kicks in. It measures the IntelliTune complex impedance of your antenna.

  • Page 6: Features

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Features • Automatically matches antennas from 6 to 1600 ohms impedance (SWR up to 32:1) • Handles 200 watts SSB/CW • Tune in less than 15 seconds, usually less than 5 seconds •...

  • Page 7: Fast Start

    7. Key your transmitter to output a carrier of 10 watts CW, FM or AM. 8. Press and hold the [TUNE] button on the MFJ-928 for one second to start the automatic tuning process. When completed, check to ensure an SWR of 2.0 or less before increasing RF power.

  • Page 8: Front Panel

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Front Panel Figure 2. MFJ-928 Front Panel. • SWR LED: A green LED that illuminates when the SWR is 1.5 or less. • TUNE LED: A red LED that illuminates when the automatic tuning is in progress.

  • Page 9: Ant Button

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Note: During the tuning process, the tuner will make some noise. These are the relays switching at a very fast pace and it is normal operation. Do not be alarmed. • ANT Button: Has two different functions based on the length of time you press and hold it before releasing.

  • Page 10: Back Panel

    The tuner requires 12 volts DC at up to 750 milli-amps. The use of a regulated supply is not mandatory but is recommended for best performance. An optional 12 volts DC 1.5 amp power supply, the MFJ-1316, is available from MFJ Enterprises, Inc. WARNING: Do not apply voltages greater than 18 volts to this unit, or permanent damage to the unit may result.

  • Page 11: Figure 6. Alinco Interface Cable

    WARNING: Make sure the +13.8 volts connection on the radio’s tuner port is capable of supplying at least 750 mA of current, since the MFJ-928 uses up to 750 mA. Jumper JP2, located behind the front panel circuit board, selects the radio to be connected to the Radio Interface connector.

  • Page 12: Figure 7. Icom Interface Cable

    Pin 6 (+13.8V) connects to pins 2 and 3 of Radio Interface Plug. Figure 8. Kenwood Interface Cable. The MFJ-5114Y interface provides power and control between a Yaesu radio and the MFJ automatic tuner. Supported Yaesu radios are FT-100, FT-817, FT-857, FT-897, and any Yaesu radio with compatible CAT system.

  • Page 13: Transmitter

    MFJ automatic tuner. Supported Yaesu radios are FT-857, FT-897, and any Yaesu radio that supports the Yaesu FC-30 tuner. Make sure to set jumper JP2 to the “I” position to use the MFJ-5124Y3. Press and hold in the [A](TUNE) key on the radio for one second to initiate automatic tuning.

  • Page 14: Installation

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Installation WARNING ● Never operate the tuner with its cover removed. Contact with the components inside the tuner while transmitting will result in painful RF burns. ● Locate the tuner so that the rear terminals are not accessible during operation. The single wire connection may have high voltage while transmitting.

  • Page 15: Miscellaneous

    L- network is properly tuned. These limits are built into the MFJ-928 to prevent matching of extreme load impedance outside the tuner’s specification, which may result in excess voltage and/or current across the tuner’s components.

  • Page 16: Morse Code And Beeps

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Morse Code and Beeps If not enough power is applied for tuning (less than two watts), “QRO” (dah-dah-di-dah di-dah-dit dah- dah-dah) will be sent on CW. Increasing the input power above two watts ends this message.

  • Page 17: Grounding Hints

    For operator safety, a good outside earth ground or water pipe ground should always be installed and connected to the case of the MFJ-928. Make certain the safety ground also connects to the transmitter and other station accessories. A wing-nut post marked GROUND is provided for ground connections.
  • Page 18 MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual wavelength feedline converts the low antenna impedance to a very high impedance at the tuner. A similar problem occurs if the antenna has an extremely high impedance and the transmission line is a multiple of a half-wavelength.

  • Page 19: Appendices

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Appendices POWER-ON OPERATIONS (Press and hold buttons while turning on the power.) TUNE POWER Press and hold to start the self test. TUNE POWER Press and hold to delete current antenna memory.

  • Page 20: Delete Entire Antenna Memory

    Within four seconds of releasing [ANT], press the [TUNE] button once. After releasing [TUNE] for four seconds, beep three times and resume normal operation. WARNING: If the MFJ-928 is behaving weirdly or acting erratic, try resetting the tuner to factory defaults. Delete Entire Antenna Memory To delete an entire antenna memory (all four banks), first select the antenna (1 or 2) that you want to delete.

  • Page 21: Self Test

    Instruction Manual Self Test A self-test routine will check the functions of the MFJ-928. This routine checks the LEDs, the front- panel buttons, the internal memory, the audio circuitry, and the power-down circuitry. During the self- test, you may stop the test by turning off the unit; however, this should NOT be done during the memory test or the memory could be corrupted.

  • Page 22: Power-Down Circuit Test

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual Power-Down Circuit Test When the 12 VDC power to the tuner is turned off, the tuner saves all settings to non-volatile memory. The Power-Down Circuit Test checks the power-down detection circuitry. It is recommended that this test be done immediately after the regular self-test described above.

  • Page 23: Frequency Counter Calibration

    50-ohm dummy load, three 50-ohm SO-239 coax cables, a Phillips screwdriver, a tuning tool or small flat blade screwdriver, and a cross-needle wattmeter (available only at MFJ factory). Therefore, this calibration can only be done at MFJ factory.

  • Page 24: In Case Of Difficulty

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual 6. Press and hold only the [ANT] button while turning the power on. Both LEDs will blink until the button is released. 7. Within four seconds of releasing [ANT], press the [TUNE] button seven times.

  • Page 25: Technical Assistance

    If you have any problem with this unit first check the appropriate section of this manual. If the manual does not reference your problem or your problem is not solved by reading the manual, you may call 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 26: Circuit Block Diagram

    MFJ-928 Compact IntelliTuner Automatic Antenna Tuner Instruction Manual © 2005 MFJ Enterprises, Inc.
  • Page 27 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 warranty are satisfied.
  • Page 28 MFJ ENTERPRISES, INC. MFJ-928 Manual 300 Industrial Park Road Version 0A Starkville, MS 39759 Printed In U.S.A. 10/2005...

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