TM 11-492-292-15
b. Align the compass transmitter magneti-
(j) P O W E R O N - P O W E R O F F :
cally as follows:
POWER ON.
(1) Set the MODE SELECTOR switch to
(2) Adjust the VOLTS ADJUST control
CAL.
until the EXC VOLTS meter indicates 23.5
volts. Check to see that the FREQUENCY
(2) Rotate the turntable assembly until the
meter indicates 400 5 cycles per second (cps).
HEADING and ERROR readout indicates 0
DEGREES 10 MINUTES. Set the turntable
(3) Rotate the monitor assembly to sight
assembly azimuth scale to 0o.
the compass swing target established during the
area magnetic survey (line 8-4 on area mag-
(3) Rotate the turntable assembly to head-
ings of 0, 90, 180, and 270o, tapping the com-
netic survey data sheet (fig. 4-4) ). The target
bearing should be permanently marked at the
pass transmitter lightly at each heading. Record
monitor location. Set the azimuth scale to target
the ERROR readout indication at each heading
bearing. Record the bearing on line A-1 of
in table B of the swing data sheet,
compass swing data sheet (fig. 9-5).
(4) Algebraically add the four errors and
(4) Rotate the monitor assembly to head-
divide the sum by 4. If the resultant index error
ings (azimuth scale settings ) of 0, 90, 180, and
exceeds 10 minutes, change the azimuth scale
270. Record the control console ERROR read-
setting by the amount and in the direction of
out indications at each heading in table A of
the index error.
the swing data sheet.
(5) Rotate the turntable assembly to head-
ing of 0. Record the ERROR readout indication
NOTE
three times, tapping the compass transmitter
Errors are positive when white divi-
lightly before each reading. Algebraically add
sions appear in the ERROR readout,
the three errors and divide the sum by 3. Re-
and negative when red divisions ap-
cord the resultant average error in table B of
pear.
the swing data sheet.
(5) Algebraically add the four errors and
(6) Repeat the procedure given in (5)
divide the sum by 4. Record the resultant moni-
above for headings of 90, 180, and 270.
tor index error on line A-2 of swing data sheet.
Make recordings in appropriate columns of
(6) Record the turntable location correc-
table B of the swing data sheet.
tion (from line 10B of area magnetic survey
(7) Algebraically add the four average
data sheet (fig. 4-4) on line A-3 of the swing
errors and divide the sum by 4. Record the
data sheet.
resultant compass transmitter index error on
(7) Algebraically add values recorded on
line B-1 of the swing data sheet. If the index
lines A-2 and A-3 of swing data sheet. Record
error exceeds 15 minutes, repeat the proce-
the resultant corrected monitor index on line
dure given in (2) above.
A4 of swing data sheet. This value represents
(8) Algebraically subtract the compass
initial magnetic bearing of north-south line.
transmitter index error (line B-1) from each
(8) Rotate monitor assembly to heading
average error (table B) and record as corrected
of 0. Record the ERROR readout indication
manual swing error in table B of the swing
as a monitor zero error on line A-5 of swing
data sheet.
data sheet. This value serves as a reference to
(9) Set the MODE SELECTOR switch to
determine subsequent shifts in the direction of
MON. Record the ERROR readout indication
the earth's magnetic field.
as monitor zero error on line B-2 of the swing
(9) Set the control console AREA COMP
data sheet.
control dial to the area compensation value
NOTE
established during the area magnetic survey
If the compass transmitter has been
(line 10D of area magnetic survey data sheet)
previously calibrated with an AN/
and record the value on line A-6 of the swing
ASM-339(V)1, the values of E1
data sheet.
9-6
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