LDG AT-897 User Manual

FR
FR
SWR
/1
/1
−
+
=
SWR is measured using a device called an “SWR bridge”, inserted in the transmission line between the
transmitter and antenna. This circuit measures forward and reverse power from which SWR may be
calculated (some meters calculate SWR for you). More advanced units can measure forward and reverse
power simultaneously, and show these values and SWR at the same time.
An antenna tuner is a device used to cancel out the effects of antenna reactance. Tuners add capacitance to
cancel out inductive reactance in the antenna, and vice versa. Simple tuners use variable capacitors and
inductors. The operator adjusts them by hand while observing reflected power on the SWR meter until a
minimum SWR is reached. Your LDG AT-897 automates this process.
No tuner will fix a bad antenna. If your antenna is far from resonance, the inefficiencies inherent in such
operation are inescapable; it’s simple physics. Much of your transmitted power may be dissipated as heat in
the tuner, never reaching the antenna at all. A tuner simply “fools” your transmitter into behaving as though
the antenna were resonant, avoiding any damage that might otherwise be caused by high-reflected power.
Your antenna should always be as close to resonance as practical; this is especially important for low-
power operation.
where F = Forward power (watts), R = Reflected power (watts)
Forward Power (Watts)
20 30 40 50 60 70 80 90 100
2 1.92 1.70 1.58 1.50 1.45 1.41 1.38 1.35 1.33
4 2.62 2.15 1.92 1.79 1.70 1.63 1.58 1.53 1.50
6 3.42 2.62 2.26 2.06 1.92 1.83 1.75 1.70 1.65
8 4.44 3.14 2.62 2.33 2.15 2.02 1.92 1.85 1.79
10 5.83 3.73 3.00 2.62 2.38 2.22 2.09 2.00 1.92
12 7.87 4.44 3.42 2.92 2.62 2.41 2.26 2.15 2.06
14 11.24 5.31 3.90 3.25 2.87 2.62 2.44 2.30 2.20
16 17.94 6.42 4.44 3.60 3.14 2.83 2.62 2.46 2.33
18 37.97 7.87 5.08 4.00 3.42 3.06 2.80 2.62 2.47
20 - 9.90 5.83 4.44 3.73 3.30 3.00 2.78 2.62
22 - 12.92 6.74 4.94 4.07 3.55 3.21 2.96 2.77
24 - 17.94 7.87 5.51 4.44 3.83 3.42 3.14 2.92
26 - 27.96 9.32 6.17 4.85 4.12 3.65 3.32 3.08
28 - 57.98 11.24 6.95 5.31 4.44 3.90 3.52 3.25
30 - - 13.93 7.87 5.83 4.79 4.16 3.73 3.42
32 - - 17.94 9.00 6.42 5.18 4.44 3.95 3.60
34 - - 24.63 10.40 7.09 5.60 4.75 4.19 3.80
36 - - 37.97 12.20 7.87 6.07 5.08 4.44 4.00
38 - - 77.99 14.60 8.80 6.60 5.44 4.71 4.21
40 - - - 17.94 9.90 7.19 5.83 5.00 4.44
42 - - - 22.96 11.24 7.87 6.26 5.31 4.68
44 - - - 31.30 12.92 8.65 6.74 5.65 4.94
46 - - - 47.98 15.08 9.56 7.27 6.02 5.22
48 - - - 97.99 17.94 10.63 7.87 6.42 5.51
50 - - - - 21.95 11.92 8.55 6.85 5.83
Reflected Power (Watts)
SWR Lookup Table
Find SWR at intersection of
forward power column and
reflected power row
.
11

LDG AT-897 Specifications

General

Brand	LDG
Model	AT-897
Category	Tuner
Language	English