MFJ-993B IntelliTuner Automatic Antenna Tuner
Instruction Manual
2005-2012 MFJ Enterprises, Inc.
12
•
Random wire to the WIRE binding post on the back of the tuner (and remove the jumper wire).
Note the back panel warning:
Do not connect WIRE and ANTENNA 1 at same time!
When a
single wire antenna is connected it “becomes” ANTENNA 1.
Note:
Route all random wire antennas safely to prevent RF burn hazard.
•
For a balanced feedline (open wire, twinlead, or twin-axial lines), place a jumper wire as
indicated on the back panel and connect the balanced feedline to the BALANCED LINE binding
posts. This antenna becomes ANTENNA 1. See “Antenna System Hints” on page 24.
4.
A GROUND post is provided for an RF ground connection. See “Grounding Hints” on page 23.
5.
Connect a 12 to 15 VDC power source to the input jack labeled POWER.
SWR/Wattmeter
The backlit cross-needle meter measures forward power,
reflected power, and SWR, and operates whenever the tuner is
powered on. Forward power up to 300 watts is displayed on the
left-hand FORWARD meter scale. Reflected power up to 60
watts is read on the right-hand REFLECTED meter scale. For
low-power tuning, meter ranges of 30 watts forward and 6 watts
reflected are available. Divide the readings on these scales by
ten when in the low power meter range.
The meter can be set to low, high, or auto range. Auto range
automatically sets the meter scales according to the input RF power to the tuner. Forward power greater
than 30 watts or reflected power greater than six watts automatically sets the meter to the high power
range. Forward power less than 25 watts and reflected power less than four watts automatically set the
meter to the low power range. To cycle the meter range among low, high, and auto range, press the
[TUNE] and [L-DN] buttons simultaneously. The forward needle will read “300” for high range, “30” for
low range, and “100” for auto range until the buttons are released. When auto range is enabled, a two-dot
vertical segment (low range) or a three-dot vertical segment (high range) appears in the lower right corner
of the Range indicator on the main LCD screen. One beep indicates high range is selected; two beeps
indicate low range; three beeps indicate auto range. Refer to Figures 13 and 14 for the on-screen Range
indicator.
SWR is calculated from the forward and reflected power
measurements as shown by the equation at the right. The SWR is
read from the eight red SWR curves, ranging from 1.0 to infinity,
by observing the point where the forward and reflected power
needles cross on the red curved scales across the center of the
meter. No cumbersome or time-consuming SWR sensitivity
adjustments are required with this meter. Figure 9 shows an SWR
of approximately 2.0.
The meter also indicates various operational states of the tuner. Refer to “Meter Codes and Audible
Beeps” on page 21 for more details.
The MFJ-993B also includes an SWR bar meter and an audio SWR indicator, selectable by pressing [L-
UP] and [L-DN] buttons simultaneously. It also has bar meters for forward and reflected power.
0
1
0
30
50
100
200 30
0
0
5
20
40
60
8
5.0
3.0 2.0
1.5 1
.2
Hi x1
Lo x.1
400-3083
1
10
Figure 9. SWR/Wattmeter.
reflected power
1
forward power
reflected power
1
forward power
SWR
+
=
−
