MFJ-993BRT 300 Watt IntelliTuner
TM
Automatic Remote Antenna Tuner Instruction Manual
© 2011 MFJ Enterprises, Inc
MFJ-993BRT Version 1A
5
Operation
1. Turn on the MFJ-993BRT power via the MFJ-4117 Bias TEE. With power off the Tuner is in
Bypass mode. With power on the MFJ-998 wakes up in bypass mode until RF is supplied to the
tuner.
2. Initial Tuneup:
a. Transmit a low power signal (5 to 20 watts). Any amplifier must be OFF LINE! Wait while
the tuner finds a tuning solution for that frequency. Verify that the SWR is below the
target SWR (default 1.5:1) with an in-shack SWR meter.
b. Once the tuner has found a tuning solution you are ready to operate at high power.
c. You can repeat the initial tune up on other frequencies and bands so the tuner will
memorize the settings for those frequencies and bands.
d. If the tuned SWR is higher than you prefer (though it will be within the SWR window of
the retune function) turn off the MFJ-993BRT for 2-seconds. Then turn it back on and
tune again.
3. Normal Tuneup
a. Transmit a low power signal (5 to 20 watts).
b. The tuner will check the frequency and set the tuner for the settings for that frequency if
memorized and quickly tune to those settings.
c. If the frequency is not memorized or the SWR is outside the tuning window then the tuner
will retune as in the initial tuneup.
Note: The MFJ-993BRT will sometimes not tune when changing bands. This can occur if the MFJ-
993BRT tuning solution for the previous band results in a very high SWR on the new band. This very
high SWR can reflect all input power from your transceiver. The solution is to simply cycle power to the
MFJ-993BRT when changing bands. This drops the MFJ-993BRT to bypass prior to tuning so some
forward power is sensed thus permitting a tune to occur.
4. Once the MFJ-993BRT completes tuning, you can increase power up to 300 watts PEP or 150
watts CW.
Note: When attempting to tune, the MFJ-993BRT will not tune and will bypass itself when the forward
power exceeds 75 watts and the SWR is greater than 3.0, or when the forward power exceeds 125 watts
while tuning regardless of the SWR.
WARNING
Never tune with high power.
Always use low power (5 to 20 watts) when tuning. Tuning with high power will cause voltages and
currents that may exceed the component ratings or present antenna loads that can damage an amplifier
or radio during the tuning process.
WARNING:
Do not turn the power on and off rapidly, otherwise the tuner setting memory can be corrupted and the
unit will have to be reset to factory defaults. Leave the tuner off for 1 to 2 seconds before turning it back
on.
Note: During the tuning process, the tuner will make noise as the relays switch at a very high rate. This is
normal. Do not be alarmed.
