MFJ-939 Plug&Play IntelliTuner Automatic Antenna Tuner
Instruction Manual
2006-2015 MFJ Enterprises, Inc.
1
THE BASICS
Introduction
The MFJ-939
Plug&Play Intellituner
TM
a simple to install and convenient antenna tuner for use with Icom,
Alinco, Kenwood, or Yaesu radios. The MFJ-939 comes complete with interface cable and programmed
for your particular radio.
The MFJ-939
Plug&Play IntelliTuner
TM
lets you rapidly tune any unbalanced or single-wire antenna
automatically. 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. The antenna has
eight banks of 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.
The MFJ-939
Plug&Play 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. The antenna has two sets of four banks of
memory, which can learn and remember more than 2500 frequencies and tuner settings. A total of 20000
settings.
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 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
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 minimum power to tune is approximately two watts, with maximum SWR tuning accuracy occurring
at tuning power levels of 10-20 watts.
Like all MFJ’s
IntelliTuners
TM
, the MFJ-939 supports radio tuner interfaces that are compatible with
Alinco EDX-2 tuner, Icom AH-3 and AH-4 tuners, Kenwood AT-300 tuner, Yaesu FC-30 tuner, and
Yaesu FH-1 and FH-2 remote controls.
When your station radio is upgraded or changed the MFJ-939 can be changed from one radio model to
another with the optional interface cables MFJ-5114A (for Alinco), MFJ-5114I (for Icom), MFJ-5114K
(for Kenwood); and MFJ-5114Y/Y3/Y4 (for Yaesu) that are available from MFJ Enterprises, Inc. So as
the station changes the tuner can change with the station.
The MFJ-939 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.
