MFJ-998 Legal Limit IntelliTuner Automatic Antenna Tuner
Instruction Manual
©
2007-2010 MFJ Enterprises, Inc.
1
The Basics
Introduction
The MFJ-998
IntelliTuner
TM
is a comprehensive
Full Legal Limit
automatic antenna tuning center with
an internal SWR/wattmeter and an antenna switch for two antennas. The MFJ-998 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-998 antenna output.
The MFJ-998 includes MFJ’s
Amplifier Bypass Control
TM
. This exclusive MFJ antenna tuner feature
fully protects your amplifier during tuning, and will even take your amplifier off-line should the SWR
increase above a user-defined pre-set limit.
MFJ's exclusive
InstantRecall
TM
,
IntelliTune
TM
and
AdaptiveSearch
TM
algorithms give you fast automatic
tuning with more than 20,000 non-volatile
VirtualAntenna
TM
memories. Each of the two antenna outputs
has four banks of memory; and each memory bank has over 2500 non-volatile memories for tuner
settings.
The MFJ-998
IntelliTuner
TM
includes a highly efficient switched-L network with wide matching
capability, 1.8 to 30 MHz coverage, cross-needle power meters, backlit LCD display, a radio interface
port, 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 81,664 L/C tuning combinations. The nominal tuning
ranges are 0 to 24
μ
H and 0 to 3900 pF (input) or 0 to 970 pF (output). And once a match is found, the
matching network values can be displayed so you may design your own fixed matching network if
desired.
The MFJ-998
IntelliTuner
TM
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, the tuner settings are instantly
restored and you’re ready to operate in milliseconds. Each of the two switched antenna outputs has 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
InstantRecall
TM
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
TM
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 – typically in a fraction of a
second.
If the antenna impedance is not within the tuner’s measurement range, MFJ’s
AdaptiveSearch
TM
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 tuned SWR can be set to 1.0 to 2.0. The minimum power to tune is approximately five watts,
with maximum SWR tuning accuracy occurring at tuning power levels of 10-30 watts. Manual tuning is
also available for “touching up” the tuning if desired.
