MFJ-939 Plug&Play IntelliTuner Automatic Antenna Tuner
Instruction Manual
2006-2015 MFJ Enterprises, Inc.
4
Front Panel
MODEL
MFJ-939
AUTOMATIC ANTENNA TUNER
200 Watts SSB / CW
MFJ Plug&Play IntelliTuner
TM
POWER
ALT
TUNE
SWR TUNE
Figure 2 MFJ-939 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 [TUNE] for 0.5 to 2 seconds to start the automatic tuning process. Tuning starts when
[TUNE] is released after the 0.5-2 second hold-time. 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. 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.
Note:
You can reverse the two functions above by pressing and holding the [TUNE] button for
approximately 10 seconds. I.e., when the [TUNE] button is pressed and held for 10 seconds.
You will hear two beeps. Now pressing [TUNE] momentarily starts the tuning process, and
pressing and holding the [TUNE] button for 0.5-2 seconds puts the tuner into the bypass mode.
“
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 unless a transceiver interface cable is installed. When
StickyTune
is 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. 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. Default is off.
Note:
StickyTune resets to OFF when the power is cycled or after tuning.
