TM 11-5840-360-14-1-1
NOTE: The VSWR requirement of 1.5:
5.23.3 Antenna/Waveguide VSWR Measurement
1 or less given in step 11 is based on
a 1.25:1 VSWR for the rotary joint
1. Set (master) Indicator POWER switch to ST BY.
and antenna and a waveguide VSWR
2. Attach 20 dB attenuator (Weinschel Engineering
of 1.2:1 or less.
model 530A-20 or equivalent) at FORWARD port of 20
5.23.4 Transmitter Frequency Measurement
dB Directional Coupler (located in the waveguide run
1. Set (master) Indicator switches as follows:
near the output flange of Receiver Transmitter RT
a. RANGE SELECT: 24 MILES
1240).
b. POWER: ST BY
3. Connect thermistor mount (HP 478 A or
equivalent of power meter (HP 432A or equivalent) ,at
2. Attach 20 dB attenuator (Weinschel Engineering
output port of 20 dB attenuator.
model 530A 20 or equivalent) at FOR WARD port of
directional coupler.
4. At (master) Indicator associated with Receiver
Transmitter RT-1240 under test, set POWER switch to
3. Connect frequency meter (HP X532 B or
TX ON and RANGE SELECT switch to 24 MILES.
equivalent) to attenuator output using RG-214/U coaxial
cable and type N-to waveguide adapter (HP X281A or
5. Measure forward power decibels (dBm); add
equivalent).
20.0 dB power meter reading and record sum as forward
power.
4. Connect power meter (HP 532A or equivalent)
thermistor mount (HP 478A or equivalent) to frequency
6. Set (master) Indicator POWER switch to ST BY.
meter using N to--waveguide adapter.
7. Disconnect thermistor mount from attenuator
5. Set power meter for mid-scale reading. Preset
and reconnect at directional coupler REFLECTED port.
frequency meter to 9420 MHz.
8. Set (master) Indicator POWER switch to TX
6. Adjust frequency meter for maximum dip (not
ON.
less than 1.0 dB); read transmitter frequency from
9. Record power meter reading in dBm as
meter.
reflected power.
10. Calculate return loss by subtracting reflected
5.24 S-BAND RF TEST PROCEDURES
power (recorded in step 9) from forward power (recorded
in step 5).
11. Convert return loss to VSWR using the following
5.24.1 Peak Power Output Measurement
chart, verify VSWR is 1.5 or less.
1. Attach 20 dB attenuator (Weinschel Engineering
model 530A 20 or equivalent) at FORWVARD port of 20
RETURN LOSS
RETURN LOSS
dB Directional Coupler (located in the waveguide run
VSWR
(dB)
VSWR
(dB)
near the output flange of Receiver Transmitter RT
1241).
17.391
1
1.196
21
2. Connect thermistor mount (HP 478A or
8.724
2
1.173
22
equivalent) of power meter (HP 432A or equivalent) at
5.848
3
1.152
23
output port of 20 dB attenuator.
4.419
4
1.135
24
3. At (master) Indicator associated with Receiver
3.570
5
1.119
25
Transmitter RT 1241 under test, set POWER switch to
3.010
6
1.106
26
TX ON and RANGE SELECT switch to 24 MILES.
2.615
7
1.094
27
2.323
8
1.083
28
NOTE:
The
values
given
in
2.100
9
1.074
29
parentheses in the following steps
1.925
10
1.065
30
indicate the nominal values that
1.785
11
1.058
31
should be obtained.
1.671
12
1.052
32
4. After three minute delay, observe power meter
1.577
13
1.046
33
reading (4.5 mW or greater); multiply reading by 104
1 499
14
1.041
34
(attenuation factor) and record result as average power
1 433
15
1.036
35
(45 W) .
1.377
16
1.032
36
1.329
17
1.029
37
5. At Receiver Transmitter RT-1241, connect
1.288
18
1.026
38
oscilloscope to U4 pin 8 on A6 Pulse Logic PCB.
1.253
19
1.023
39
1.222
20
1.020
40
5-120
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