MFJ-993B IntelliTuner Automatic Antenna Tuner
Instruction Manual
2005-2012 MFJ Enterprises, Inc.
31
2.
Remove the cover from the tuner (12 screws) with a Phillips screwdriver.
3.
Connect the 50-ohm dummy load to the ANTENNA 1 connector; connect the wattmeter between the
transmitter and the TRANSMITTER connector on the tuner.
4.
Turn on the power to the transmitter. Using a frequency in the middle of the HF band, such as 7.253
MHz, for calibration is recommended.
5.
Press and hold
both
the [C-UP] and [L-UP] buttons while turning the tuner power on.
6.
A message
CAL CAP AND FWD
will display and both meter needles will bounce. Key the
transmitter to output 100 watts and adjust trimmer capacitor C91 for minimum reflected power.
Notice the reflected meter movement is exaggerated for easier calibration.
7.
Key the transmitter to 100 watts output and adjust the FWD trimpot R72 until the display shows
forward power of
FWD=100
watts. The forward meter also should indicate 100 watts.
8.
Press the [TUNE] button. A message
REVERSE, CAL REF
displays and the reflected meter goes
to full scale.
9.
Turn off the transmitter and reverse the ANTENNA 1 and TRANSMITTER connections; that is,
connect the 50-ohm dummy load to the TRANSMITTER connector and connect the
transmitter/wattmeter to the ANTENNA 1 connector.
10.
Turn on the transmitter’s power.
11.
Key the transmitter to 100 watts output and adjust the REF trimpot R71 until the display shows
reflected power of
REF=100
watts. The forward meter (yes, the forward meter) also should indicate
100 watts; the reflected meter is at full scale.
12.
Press the [TUNE] button to end calibration.
13.
Turn off the power to the tuner and the transmitter.
14.
Remove the transmitter/wattmeter and the 50-ohm dummy load from the tuner.
15.
Secure the cover back onto the tuner.
16.
Connect your transmitter to the TRANSMITTER connector and connect your antenna to the
appropriate antenna connector on the tuner.
Frequency Counter Calibration
To calibrate the frequency counter, you will need a transmitter, a 50-ohm dummy load, two 50-ohm SO-
239 coax cables, a Phillips screwdriver, and a tuning tool or small flat blade screwdriver.
WARNING:
Do not touch anything inside the tuner during operation! Serious, painful RF
burns can result.
WARNING:
Never operate the MFJ-993B with its cover removed; dangerous voltages and
currents can be present during operation. Never exceed tuner specifications.
1.
Turn off the power to the tuner and the transmitter.
2.
Remove the cover from the tuner (12 screws) with a Phillips screwdriver.
3.
Connect the 50-ohm dummy load to the ANTENNA 1 connector; connect the transmitter to the
TRANSMITTER connector on the tuner.
4.
Turn on the power to the transmitter. Set and lock the frequency to
exactly
29.000 MHz.
5.
Press and hold
both
the [C-DN] and [L-DN] buttons while turning the tuner power on. Both meter
needles will go to full scale and a message
CAL FREQ 29.000
will display.
6.
Key the transmitter to output about 10 watts. Adjust trimmer capacitor C118 (located between the
two big integrated circuits) until the tuner displays a frequency of
29.000 MHz
and the meter
needles settle at the 0 watt marks. Notice the meter movement is exaggerated for easier calibration.
Nominal tolerance of the frequency counter is ±1 kHz.
7.
Turn off the power to the tuner and the transmitter.
8.
Secure the cover back onto the tuner.
