MFJ MFJ-994BRT MFJ-

INSTRUCTION MANUAL

COPYRIGHT 2010 MFJ ENTERPRISES, INC.

Model MFJ-994BRT

CAUTION: Read All Instructions Before Operating Equipment

MFJ ENTERPRISES, INC.

VERSION 1A

 2011 MFJ Enterprises, Inc. i

300 Industrial Park Road

Starkville, MS 39759 USA

Tel: [phone] Fax: [phone]

C

MFJ-994BRT HF Automatic Remote Antenna Tuner Instruction Manual

Contents

THE BASICS

Introduction ......................................................................................................................................1

Features...........................................................................................................................................2

Specifications...................................................................................................................................2

Fast Start..........................................................................................................................................3

Internal components.........................................................................................................................4

C-UP and C-DN Buttons .....................................................................................................4

L-UP and L-DN Buttons ......................................................................................................4

AUTO Button.......................................................................................................................4

TUNE Button.......................................................................................................................4

POWER Button ...................................................................................................................4

Connections .....................................................................................................................................5

Transmitter..........................................................................................................................5

Ground ................................................................................................................................5

Wire.....................................................................................................................................5

Antenna...............................................................................................................................5

Installation........................................................................................................................................6

MISCELLANEOUS

Antenna Memory..............................................................................................................................7

Intellitune Algorithym........................................................................................................................7

LC Limits ..........................................................................................................................................7

Tuner Status Indicators....................................................................................................................8

Foldback Circuit ...............................................................................................................................8

Grounding Hints ...............................................................................................................................9

Antenna System Hints......................................................................................................................9

Location...............................................................................................................................9

Matching Problems .............................................................................................................9

APPENDICES

Firmware Version Number.............................................................................................................11

Resetting the Tuner........................................................................................................................11

Factory Defaults............................................................................................................... 11

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

Total Reset........................................................................................................................12

Self Test.........................................................................................................................................12

Power Down Circuit Test................................................................................................................13

Relay Test......................................................................................................................................13

Frequency Counter Calibration......................................................................................................14

SWR Bridge Calibration .................................................................................................................15

In Case of Difficulty ........................................................................................................................15

Technical Assistance .....................................................................................................................16

List of Accessories .........................................................................................................................16

Block Diagram................................................................................................................................17

 2011 MFJ Enterprises, Inc. ii

MFJ-994BRT HF Automatic Remote Antenna Tuner Instruction Manual

The Basics

Introduction

The MFJ-994B IntelliTunerTM lets you rapidly tune unbalanced, single-wire, or balanced (with external
balun) antennas automatically.

MFJ's exclusive InstantRecallTM, IntelliTuneTM and AdaptiveSearchTM algorithms give you fast automatic
tuning with more than 10,000 non-volatile VirtualAntennaTM memories. There are four banks of memory,
and each memory bank has over 2500 non-volatile memories for tuner settings.

The MFJ-994B IntelliTunerTM includes a highly efficient switching L-network with wide matching
capability, 1.8 to 30 MHz coverage, cross-needle power meters, an accessory remote control port, a radio
interface port, and heavy-duty 16 amp/1000 volt relays. It is rated at 600 watts PEP SSB, 600 watts CW,
and 500 watts continuous carrier modes. This makes the MFJ-994B perfect for use with modern high
power output transceivers and Ameritron AL-811/ALS-600/ALS-500 amplifiers, as well as other popular
HF power amplifiers limited to no more than 600 watts output power.

A maximum of 192 values of capacitance and 192 values of inductance are available. With the
inductance switched between the input and output side, this provides a total of 73,728 L/C tuning
combinations. The nominal tuning ranges are 0 to 2950 pF and 0 to 17 µH.

The MFJ-994B IntelliTuner
minimum SWR and remembers the frequency and tuner settings, safely stored in non-volatile memory.
The next time you operate on that frequency (or close to it), the tuner settings are instantly restored and
you’re ready to operate in milliseconds. There are four banks of memory, which can learn and remember
more than 2500 frequencies and tuner settings per bank.

When you key your transmitter, MFJ’s InstantRecallTM checks its memory to see if you have operated on
that frequency before. If so, tuning is instantaneous and you’re ready to operate. If not, MFJ’s

IntelliTuneTM 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 – typically in a fraction of a
second.

If the antenna impedance is not within the tuner’s measurement range, MFJ’s AdaptiveSearchTM
algorithm goes into action. Frequency is measured and relevant component 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.

The target tuned SWR can be set to 1.5 or 2.0. The minimum power to tune is approximately two watts,
with maximum SWR tuning accuracy occurring at tuning power levels of 10-20 watts. Manual tuning is
also available for “touching up” the tuning if desired.

The MFJ-994B tuner enters a “sleep” mode when idle and when no transmit signal is present, turning off
the microprocessor clock to avoid the generation of spurious signals.

TM

learns and remembers. When you transmit, it automatically adjusts for

 2011 MFJ Enterprises, Inc. i

MFJ-994BRT HF Automatic Remote Antenna Tuner Instruction Manual

Features

• Automatically matches antennas from 12 to 800 ohms impedance

• Handles 600 watts PEP SSB/600 watts CW/500 watts constant carrier

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

• Over 10,000 non-volatile memories for tuner settings

• Four memory banks with over 2500 memories per bank

• Highly efficient switching L-network matching circuit

• 1.8 to 30 MHz continuous frequency coverage

• Selectable target SWR 1.5 or 2.0 (default is 1.5)

• Selectable SWR threshold 0.5, 1.0 or 1.5 (default is 0.5 above target SWR)

• Lighted cross-needle SWR/wattmeter with high, low and auto range options

• Built-in frequency counter for remembering frequency-specific matching values

• SO-239 coax fed antenna connector

• Connector for random wire or single wire antennas

• Optional remote control

• Optional radio interface cables for compatible radios

Specifications

• Impedance matching range : 12 to 800 ohms

• SWR matching range : Up to 4:1 for < 50 ohms and up to 16:1 for > 50 ohms

• Minimum power for tuning : 2 watts (optimum SWR tuning accuracy occurs at 10-20 watts)

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

• RF power limit : 600 watts PEP SSB/600 watts CW/500 watts constant carrier

• Frequency range : 1.8 to 30 MHz continuous coverage

• Frequency counter accuracy : ±1 kHz across HF bands

• Capacitance range : 0 to 2950 pF (192 values)

• Inductance range : 0 to 17 µH (192 values)

• Relay rating : 16 amp 1000 volts

• Relay electrical life : 100,000 operations

• Relay mechanical life : 10 million operations

• Memory endurance : 1 million write cycles

• Memory data retention : > 200 years

• Power requirements : 12 - 15 volts DC

• Current consumption : 850 mA or less

• Dimensions (connectors not incl.) : 10.1 × 2.8 × 9.2 in; 257 × 71 × 234 mm (w × h × d)

• Weight : Approx. 3.7 lb; 1.68 kg

† Specifications and design are subject to change without notice.

 2011 MFJ Enterprises, Inc. 2

MFJ-994BRT HF Automatic Remote Antenna Tuner Instruction Manual

DC / RF

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 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 (2-10 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 transmitter to the “RF IN/OUT” coaxial connector on the MFJ-4117 Bias-Tee using
a 50-ohm coaxial cable. (See Figure 1) This is the RF signal input connector.

2. Connect a 12-15 VDC voltage source capable of supplying at least 850 milli-amps to the “DC
IN\OUT” jack on the MFJ-4117 Bias-Tee. This is your DC voltage input connector.

3. Connect the “RF/DC OUT/IN” coaxial connector on the MFJ-4117 Bias-Tee to the

TRANSMITTER connector on the MFJ-994BRT Intellituner using 50-ohm coaxial cable. The
MFJ-994BRT Intellituner will recover the RF and DC signals.

4. Connect your coax-fed antenna to the ANTENNA connector using a 50-ohm coaxial cable, or
connect your random wire to the WIRE binding post.

5. Connect your ground connection to the GROUND post.

6. Key your transmitter to output a carrier of 2-20 watts CW, FM or AM. The SWR should be auto­tuned to less than 1.5:1. This can be verified with an external SWR meter if desired.

Note: If an amplifier is in-line, it should always be bypassed prior to tuning.

7. You are now ready to transmit at full power.

Note: During the automatic tuning process, the tuner will make some noise. These are the relays

switching at a very high rate and is normal. Do not be alarmed.

12-15

VDC
input

1.8-30 MHz
RF

input

MFJ-4117

Bias Tee

Figure 1: MFJ-994BRT and MFJ-4117 Installation Block Diagram

MFJ-994BRT

Intellituner

ANTENNA
OR

RANDOM
WIRE

 2011 MFJ Enterprises, Inc. 3

MFJ-994BRT HF Automatic Remote Antenna Tuner Instruction Manual

Note: To use the Random WIRE binding post, make sure to remove the antenna, if any, from

the ANTENNA connector.

Internal Components

The MFJ-994BRT was designed for remote operation with no manual operation required. The tuning
process starts automatically when the transmitter is keyed with at least two watts of power when the SWR
is greater than 2:1. The MFJ-994BRT has been pre-set with default settings at the MFJ Factory.
However, if you remove the unit from the box, you can change the default settings as well as verify proper
operation of the unit. The following will guide you through the process. The control board is mounted
upside down so will have to be unmounted before any changes are to be made.

• C-UP and C-DN Buttons: Used to manually increase or decrease the capacitance of the L-network

matching circuit. The capacitance range is 0 to 2950 pF. The upper limit of capacitance, dependent
on frequency, is restricted to limit the maximum voltage and current across the tuner’s components.

Note: Pressing [C-UP] and [C-DN] simultaneously toggles the capacitor between the input

and output sides of the L-network. Forward needle bounces to the 30-watt mark when
the capacitor is on the transmitter side. Reflected needle bounces to the 5-watt mark
when the capacitor is on the antenna side.

• L-UP and L-DN Buttons: Used to manually increase or decrease the inductance of the L-network

matching circuit. The inductance range is 0 to 17 µH. The upper limit of inductance, dependent on
frequency, is restricted to limit the maximum voltage and current across the tuner’s components.

Note: Pressing [C-DN] and [L-DN] simultaneously places the tuner in bypass mode. The

reflected meter needle momentarily bounces to the 20-watt mark to indicate this. RF
from the transmitter goes directly to the antenna with no matching.

• AUTO Button: Used to select automatic or semi-automatic tuning mode. Button out selects

automatic mode – the tuning routine is automatically started when 2-20 watts of power is applied and
the SWR is a preset amount above the preset target SWR.

Note: If an amplifier is in-line, it should always be bypassed prior to tuning.

• 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. RF from the transmitter
goes directly to the antenna with no matching.

Press and hold [TUNE] for 0.5-2 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,
pressing [TUNE] will fine-tune the match for a lower SWR if possible. This function is not used in
remote operation.

• POWER Button: Used to turn the power on and off. Note that during power-on the analog meter

bounces four times to indicate the model 994. When the power is off, the tuner is bypassed (straight
through from TRANSMITTER to ANTENNA and WIRE). When power is turned on, the tuner
powers-up bypassed, but will revert to the last stored matching values or begin tuning on application
of RF power when the TUNE button is pressed – or if Automatic or Sticky-Tune is enabled.

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.

 2011 MFJ Enterprises, Inc. 4