MFJ MFJ-925 User Manual

Super-Compact IntelliTuner

Automatic Antenna Tuner

Model MFJ-925

VERSION 0A

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

MFJ-925 Super-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

ALT Button......................................................................................................................... 5

POWER Button................................................................................................................... 5

Back Panel ....................................................................................................................................... 6

Power .................................................................................................................................. 6

Radio Interface.................................................................................................................... 6

Transmitter.......................................................................................................................... 9

Antenna............................................................................................................................... 9

Ground ................................................................................................................................ 9

Installation ..................................................................................................................................... 10

MISCELLANEOUS

Antenna Memory ........................................................................................................................... 11

IntelliTune

LC Limits....................................................................................................................................... 11

Morse Code and Beeps ..................................................................................................................12

Foldback Circuit ............................................................................................................................ 12

Grounding Hints ............................................................................................................................ 13

Antenna System Hints.................................................................................................................... 13

APPENDICES

Resetting the Tuner........................................................................................................................ 15

Self Test ......................................................................................................................................... 17

Power-Down Circuit Test .............................................................................................................. 18

Relay Test ...................................................................................................................................... 18

Frequency Counter Calibration...................................................................................................... 19

Algorithm ................................................................................................................ 11

Location ............................................................................................................................ 13

Matching Problems ........................................................................................................... 13

Factory Defaults................................................................................................................ 15

Delete Entire Antenna Memory ........................................................................................ 16

Delete Antenna Memory Bank .........................................................................................16

Total Reset ........................................................................................................................ 16

MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner Instruction Manual

SWR Bridge Calibration ................................................................................................................ 19

In Case of Difficulty ......................................................................................................................20

Technical Assistance...................................................................................................................... 21

List of Accessories......................................................................................................................... 21

Circuit Block Diagram................................................................................................................... 22

FIGURES

Figure 1. Installation Block Diagram.............................................................................................. 3

Figure 2. MFJ-925 Front Panel....................................................................................................... 4

Figure 3. Button Action ..................................................................................................................5

Figure 4. MFJ-925 Back Panel .......................................................................................................6

Figure 5. Radio Interface Connector............................................................................................... 6

Figure 6. Alinco Interface Cable..................................................................................................... 7

Figure 7. Icom Interface Cable .......................................................................................................7

Figure 8. Kenwood Interface Cable ................................................................................................ 8

Figure 9. Yaesu Interface Cable (FT-100, FT-817, FT-857, FT-897) ............................................ 8

Figure 10. Yaesu Interface Cable (FT-847) .................................................................................... 9

Figure 11. Power-On Operations .................................................................................................. 15

Figure 12. MFJ-925 Circuit Block Diagram................................................................................. 22

TABLES

Table 1. Jumper JP2 Setting............................................................................................................ 7

Table 2. Memory Resolution ........................................................................................................11

Table 3. Tuner Beeps .................................................................................................................... 12

Table 4. Failure Messages............................................................................................................. 17

MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner Instruction Manual

The Basics

Introduction

The MFJ-925 IntelliTuner MFJ's exclusive InstantRecall tuning with more than 20,000 non-volatile VirtualAntenna

memory; with over 2500 non-volatile memories for tuner settings.

The tuner includes a highly efficient switching L-network with wide matching capability, 1.8 to 30 MHz coverage, a radio interface port, and heavy-duty 10 amp/1000 volt relays. It is rated at 200 watts SSB/CW.

A maximum of 256 values of inductance and 256 values of capacitance are available. With the capacitance switched between the input and output side, this provides a total of 131,072 L/C tuning combinations. The nominal tuning ranges are 0 to 24 μH and 0 to 3900 pF.

All MFJ IntelliTuners

SWR and remember the frequency and tuner settings, safely stored in non-volatile memory. The next time you operate on that frequency (or close to it) and antenna, these tuner settings are instantly restored and you’re ready to operate in milliseconds. The antenna has four banks of memory, which can learn and remember more than 2500 frequencies and tuner settings.

When you key your transmitter, MFJ’s InstantRecall

that frequency before. If so, tuning is instantaneous and you’re ready to operate. If not, MFJ’s

IntelliTune

algorithm (based on MFJ’s famous SWR Analyzer technology) kicks in. It measures the complex impedance of your antenna. Next, it calculates the components it needs and instantly snaps them in. Finally, it fine-tunes to minimize SWR, and you’re ready to operate--all in a fraction of a second.

If the antenna impedance is not within the tuner’s measurement range, MFJ’s AdaptiveSearch

algorithm goes into action. Frequency is measured and relevant components values are determined. Only those values are searched for fast tuning. If it still cannot find a match, the search is performed again using a different search pattern.

All MFJ’s IntelliTuners

Icom AH-3 and AH-4 tuners, Kenwood AT-300 tuner, and certain Yaesu radios with CAT system. Optional interface cables MFJ-5114A (for Alinco), MFJ-5114I (for Icom), MFJ-5114K (for Kenwood), MFJ-5114Y and MFJ-5114Y2 (for Yaesu) are available from MFJ Enterprises, Inc.

The tuners enter a “sleep” mode when idle and when no transmit signal is present, turning off the microprocessor clock to avoid the generation of spurious signals.

lets you rapidly tune any unbalanced or single-wire antenna automatically.

, IntelliTuneTM and AdaptiveSearch

learn and remember. When you transmit, they automatically adjust for minimum

support radio tuner interfaces that are compatible with Alinco EDX-2 tuner,

checks its memory to see if you have operated

algorithms give you fast automatic

memories. The antenna has eight banks of

MFJ-925 Super-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

• Tunes in less than 15 seconds, usually less than 5 seconds

• Over 20,000 non-volatile memories for tuner settings

• Eight memory banks with over 2500 memories per bank

• Highly efficient switching L-network matching circuit

• 1.8 to 30 MHz continuous frequency coverage

• Audio SWR meter

• Built-in frequency counter

• Built-in radio interface circuitry for compatible radios

• Built-in bias tee

• SO-239 coax fed antenna connector

• SO-239 coax to single wire adaptor

Specifications

• Impedance matching range: 6 to 1600 ohms

• SWR matching range: up to 8:1 for < 50 ohms and up to 32:1 for > 50 ohms

• Minimum power for tuning: 2 watts

• Maximum power while tuning: 100 watts with foldback, 20 watts without foldback

• RF power limit: 200 watts SSB/CW

• Frequency range: 1.8 to 30 MHz continuous coverage

• Frequency counter accuracy: ±1 kHz across HF bands

• Capacitance range: 0 to 3961 pF nominal (256 values)

• Inductance range: 0 to 24.86 μH nominal (256 values)

• Relay rating: 10 amp 1000 volts

• Relay electrical life: 100,000 operations

• Relay mechanical life: 10 million operations

• Memory endurance: 1 million erase/write cycles

• Memory data retention: > 200 years

• Power requirements: 12 - 15 volts DC, 2.1 × 5.5 mm coaxial plug, center pin positive

• Current consumption: 750 milli-amp or less

• Dimensions (approx.): 6 1/2 × 2 1/8 × 8 1/4 in. (165 × 54 × 210 mm) (width/height/depth)

• Weight (approx.): 2.3 lb. (1.04 kg)

† Specifications and design are subject to change without notice.

MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner Instruction Manual

Fast Start

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.

● Disconnect all antennas from the tuner during lightning storms.

● Always tune with low power (about 10 watts). Apply maximum power only after tuning up.

● Never exceed tuner specifications.

● Do not transmit with a high SWR for extended periods of time.

1. Connect the MFJ-925 to a 12-15 VDC voltage source capable of supplying at least 750 milli-amps.

2. Connect your transmitter to the TRANSMITTER connector using a 50-ohm coaxial cable.

3. Connect your coax-fed antenna to the ANTENNA connector using a 50-ohm coaxial cable, or connect your random wire to the ANTENNA connector through the supplied adaptor.

4. Connect your ground connection to the GROUND post.

5. Press the [POWER] button to turn on the MFJ-925 tuner.

6. Press the [ALT] button momentarily until there is one beep. One beep indicates that memory 1 is selected.

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-925 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.

9. You are ready to transmit.

Note: During the automatic 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.

Note: When the tuner power is OFF, the tuner is in bypass mode and RF from the transmitter goes

directly to the ANTENNA with no matching. When the tuner power is ON, pressing [TUNE] quickly places the tuner in bypass mode (zero inductance and zero capacitance) and indicates by one beep.

Antenna 1

Transmitter MFJ-925

50-ohm Coax

RF Ground 12 VD

Figure 1. Installation Block Diagram.

MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner Instruction Manual

Front Panel

MFJ IntelliTuner

AUTOMATIC ANTENNA TUNER

200 Watts SSB / CW

TUNE

SWR TUNE

MODEL

MFJ-925

POWERALT

Figure 2. MFJ-925 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.

• TUNE Button: Has three different functions based on the length of time you press and hold it before

releasing. Press [TUNE] quickly (less than 0.5 second) to bypass the tuner. One beep indicates bypass mode, where RF from the transmitter goes directly to the antenna with no matching. A second quick press toggles the tuner back to its last L/C setting, and the tuner responds with two beeps.

Press and hold [TUNE] for 0.5 to 2 seconds to start the automatic tuning process. The transmitter must be keyed first with at least two watts of power. When the SWR is already below the target SWR of 1.5, pressing [TUNE] will fine-tune the match for a lower SWR, if possible. When the automatic tuning is completed, a series of beeps indicates the tuned SWR where one beep indicates SWR of 1.5 or less, two beeps indicate SWR of 1.6 to 2.0, three beeps indicate SWR of 2.1 to 2.5, and four beeps indicate SWR of 2.6 to 3.0. For SWR above 3.0, “SWR” (di-di-dit di-dah-dah di-dah-dit) will be sent on CW.

“StickyTune” allows for one-handed tuning operation. Normal tuning requires keying the transmitter

with one hand and using the other hand to push the [TUNE] button to start the tuning process. To

toggle the StickyTune mode on and off, press and hold the [TUNE] button for two seconds. One beep

indicates on and two beeps indicate off. When enabled, the tuning process starts automatically when the transmitter is keyed with at least two watts of power regardless of the SWR. This works in both automatic and semi-automatic modes.

Automatic/Semi-Automatic Tuning Mode

Pressing [TUNE] and [ALT] simultaneously toggles between automatic and semi-automatic tuning mode. One beep indicates automatic mode and two beeps indicate semi-automatic mode. In automatic mode, the tuning routine is automatically started when at least two watts of power is applied and the SWR is greater than 2.5. In semi-automatic mode, the tuning routine starts only when the [TUNE] button is pressed for 0.5 to 2 seconds.

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.

MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner Instruction Manual

• ALT Button: Has two different functions based on the length of time you press and hold it before

releasing. Press [ALT] quickly (less than one second) to select the primary memory bank to use.

Press button to toggle between Memory 1 and Memory 2. One beep indicates Memory 1 and two

beeps indicate Memory 2.

Press and hold [ALT] for one second to cycle among the four secondary memory banks of the current primary memory selected. The selected bank is indicated by a series of short beeps, where one beep indicates bank A, two beeps indicate bank B, three beeps indicate bank C, four beeps indicate bank D, and five beeps indicate antenna memory is OFF. See “Antenna Memory” on page 11.

Pressing the [ALT] button will switch the antenna or bank only when there is no RF power; also, the

tuner setting for the selected antenna and bank, if available, is instantly restored from memory when enabled.

• POWER Button: Used to turn the power on and off. When the power is off, the tuner is placed in

bypass mode. When turning on the power, the tuner automatically restores all previous settings and displays the target SWR on the main screen.

WARNING: Do not turn the power on and off rapidly, otherwise the tuning setting

memory can be corrupted and the unit will have to be reset to factory defaults.

Note: When the tuner power is OFF, the tuner is in bypass mode and RF from the transmitter

goes directly to the antenna with no matching.

BUTTON ACTION

Press in to turn power on, out to turn power off.

Press less t han 0.5 second to toggle bypass mode; press and hold for 0.5 to 2 seconds to start the tuning process; press and hold for more than two seconds to toggle the StickyTune on and off.

Press less than one second to toggle between memory 1 and memory 2; press and hold for more than one second to cycle through the 2 antenna memory banks.

Press + to toggle between automatic and semi-automatic mode.

POWER

TUNE

ALT

TUNE ALT

Figure 3. Button Action.

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