TB 9-6625-1356-24
(7) Adjust attenuator to 50 dB. Record true rms voltmeter indication.
(8) Set OUTPUT ATTENUATOR switch to 0 DBM.
(9) Adjust attenuator to 40 dB. Record true rms voltmeter indication.
(10) Repeat technique of (6) through (9) above for each OUTPUT ATTENUATOR
switch setting from -10 through -40 DBM.
(11) Compute voltage difference between reference value recorded in (5) above and
voltage value recorded for each OUTPUT ATTENUATOR switch setting checked.
Example:
Voltage obtained in (5) above = 1.0050 mV
Voltage obtained at OUTPUT ATTENUATOR -30 DBM switch setting = 1.0095 mV
Voltage difference = 1.0050 - 1.0095 = -4.5 V
Voltage difference of -4.5 V yields 0.04 dB change as obtained from table 8
(12) Refer to table 8 and record attenuation change. Designate attenuation change
as +c if true rms voltmeter indicates a decrease from reference, and as -c if true rms
voltmeter indicates an increase from reference.
Table 8. Voltage Change vs. Attenuation Change
Voltage difference (V)
Equivalent attenuation change in dB(c)
0
to 1.7
0.01
1.7
to 2.8
0.02
2.8
to 4.0
0.03
4.0
to 5.1
0.04
5.1
to 6.4
0.05
6.4
to 7.5
0.06
7.5
to 8.7
0.07
8.7
to 9.8
0.08
9.8
to 11.0
0.09
11.0
to 12.2
0.10
12.2
to 13.3
0.11
13.3
to 14.5
0.12
14.5
to 15.7
0.13
15.7
to 16.8
0.14
16.8
to 18.0
0.15
18.0
to 19.2
0.16
19.2
to 20.4
0.17
20.4
to 21.5
0.18
21.5
to 22.7
0.19
22.7
to 23.3
0.20
(13) Refer to test report for attenuator and record the corrected attenuation value for
60 dB. Designate this value as a.
(14) Repeat (3) above for 50 dB. Designate this value as b.
(15) Using formula: Attenuation (a - b) c, determine attenuation value. This value
will be within limits for the OUTPUT ATTENUATOR switch settings listed in table 9.