Instruction manual

MFJ-998RT Legal Limit IntelliTuner

Automatic Remote Antenna Tuner Instruction Manual

MFJ-998RT Version 1A

The Basics

Introduction

The MFJ-998RT IntelliTuner

is a comprehensive Full Legal Limit remote automatic antenna tuning unit .

The MFJ-998RT lets you rapidly tune almost any unbalanced or single-wire antenna automatically.

Balanced feedlines may be used with an MFJ-912 1.5 kW 4:1 balun connected to the MFJ-998RT

antenna output.

MFJ's exclusive InstantRecall

, IntelliTune

and AdaptiveSearch

algorithms give you fast automatic

tuning with more than 20,000 non-volatile VirtualAntenna

memories. Each of the two antenna banks has

four banks of memory; and each memory bank has over 2500 non-volatile memories for tuner settings.

The banks allow you to save settings for several antennas giving you the flexibility to move the a tuner

between antennas or move to different locations without loosing the old settings.

The tuner includes a highly efficient switched-L network with wide matching capability, 1.8 to 30 MHz

coverage, backlit LCD display, and heavy-duty 16 amp/1000 volt relays. It is rated at 1500 watts SSB/CW

and will match impedances from 12 to 1600 ohms (SWR up to 32:1).

A maximum of 256 values of inductance and 256 values of input capacitance or 64 values of output

capacitance are available. This provides a total of 81,920 L/C tuning combinations. The nominal tuning

ranges are 0 to 24 µH and 0 to 3900 pF. And once a match is found, the matching network values can be

displayed so you may design your own fixed matching network if desired.

Like all MFJ IntelliTuners

, the MFJ-998RT learns and remembers. When you transmit, it automatically

adjusts for 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) and antenna, these tuner settings

are instantly restored and you’re ready to operate in milliseconds.

When you key your transmitter, MFJ’s InstantRecall

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 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 needed 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. The target SWR can be set at 1.0 through 2.0. The minimum power to tune is

approximately five watts. 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.