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Figure 6-4. Audio frequency test.
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TM-11-5895-1012-10 Technical Control Facility (General) Manual
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Figure 6-5. Longitudinal balance input test.
TM 11-5895-1012-10
testing except the local station acts as both trans-
(c) Remove the input signal by disconnecting
mitter and receiver in both input and output tests.
Transmission Test Set No. 1 and observe Transmission
Test Set NO. 2 voltmeter. If the voltage measured by
6-9. Single Tone Interference Test
Transmission Test Set NO. 2 does not drop in value
a. Purpose. This test will measure maximum single
when the input signal is disconnected, then the line
tone interference of circuits between stations or
noise is probably mashing the reading Of V2. This con-
within a station and determine circuit compliance with
&ion must be corrected before the test can be com-
the standard operating requirements. These inter-
pleted.
ferring tones may come from carrier leak or from
(d) If the voltage measured by Transmission
nearby equipment or systems.
Test Set NO. 2 (V2) did drop in value when the input
b. Test Equipment. Test equipment required to per-
signal was disconnected then calculate the Longi-
form this test consists of a Frequency Selective Volt
tudinal Balance using the following formula:
meter and terminating plugs (600 ohms) and patch
Longitudinal Balance (db) = 20 Log10V1/V2.
cords.
(4) Performance Standard. Minimum Longitu-
c. Station-to-Station Test. Contact the distant sta-
dinal Balance is 40 db.
tion and arrange for one station to act as transmitter
d. Station-to-Station Output Test. Contact distant
and one as receiver. Perform the procedure below and
station and arrange for one station to act as trans-
then reverse roles and repeat the procedure.
mitter and one as receiver. Perform the procedure
(1) Transmitting Circuit. If the local station is to
below and then reverse roles and repeat the procedure.
act as transmitter, prepare the transmitting circuit
(1) Transmitting Circuit. If the local station is to
shown in figure 6-7.
act as transmitter, prepare the transmitting circuit
(2) Receiving Circuit. If the local station is to act
shown in figure 6-6 and set the equipment as follows:
as receiver, prepare the receiving circuit shown in
(a) Transmission test set jumpered as shown in
figure 6-7 and set the frequency selective voltmeter as
figure 6-6 with voltmeter function switch to on.
follows:
(b) Patch panel impedance selectors at 600
(a) Input impedance set for 600 ohms.
ohms.
(b) Input attenuator set so that the maximum
(c) Patch panel frequency selector at less than 5
level of the single tone interference is included in the
KHz.
measuring range of the voltmeter.
(2) Receiving Circuit. If the local station is to act
(3) Procedure.
as receiver, prepare the receiving circuit shown in
(a) Slowly sweep the frequency control of the
figure 6-6 and set the equipment as follows:
frequency selective voltmeter through the frequency
(a) Transmission test sets jumpered as shown in
range of the channel under test.
figure 6-6 with voltmeter function switches to on.
(b) Record the power level (in dbm) of the peaks
(b) Patch panel impedance selectors at 600
indicated by the frequency selective voltmeter. Con-
ohms.
vert this measurement to dbm0 by allowing for the
(c) Patch panel frequency selectors at less than
relative level of the transmission level point at which
5 KHz.
the measurement was made.
(3) Procedure.
(c) Convert this level from dbm0 to dbm0 us-
(a) At the transmitting station, set the fre-
ing the conversion chart in figure 6-8. Read the fre-
quency of Transmission Test Set No. 1 to a value near
quency of the interferring tone from the frequency
the top of the audio bandwidth (approximately 2700
selective voltmeter and then find the conversion factor
Hz). Adjust transmission Test Set No. 1 for a level of
for the frequency in figure 6-8. Then, dbrnc0 = dbm0
- 10 dbm0 as read at the receiving station on Trans-
+ conversion factor.
mission Test Set No. 3 voltmeter. Note this level and
(4) Performance Standard. Refer to the Technical
label it V1.
Services Schedules (table 4-2) for the maximum allow-
(b) Adjust the range control of Transmission
able noise for the channel being tested. The maximum
Test Set No. 2 for a suitable sensitivity and measure
single tone interference (measured in dbrnc0) will not
the voltage displayed on Transmission Test Set No. 2
exceed the level specified by the Technical Services
voltmeter. Note this voltage and label it V2.
Schedule.
(c) Calculate the longitudinal balance of the out-
d. In-Station Test. In-station testing is accom-
put circuit using the following formula:
plished in the same manner as station to station test-
Longitudinal Balance (db) = 20 Log10V1/V2.
ing except the local station acts as both transmitter
(4) Performance Standard. The permissable mini-
and receiver.
mum longitudinal balance is 40 db.
6-10. Impulse Noise Test
e In-Station Testing, In-station testing is ac-
a. Purpose. This test will measure impulse noise on
complished in the same manner as station to station

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