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5.7 Transmitter Adjustments
5.7.1 Autoshutdown and Audio Alignment
Introduction : The following procedures should be performed fol-
lowing the alignment procedures. If voice modulation is not used,
skip section "Autoshutdown and Audio Alignment," and go directly
to section "Autoshutdown Adjustment - Nonvoice System."
A. Preliminary:
i.
Place the Autoshutdown ON/OFF switch S1 in the OFF position.
See Autoshutdown PWB Schematic and Assembly in Section 2,
and the "Control and Test Points Positions" in this section.
2.
Measure the audio line level at the input to the transmitter
case using a FLUKE 8020B or equivalent digital multimeter.
The average level should be -28 dBm (0.031VRMs) or greater.
3.
Set switch $1 on the Audio PWB as follows:
a.
For high level audio line inputs (-15 dBm to +7 dBm),
set to C2 position.
b.
For low level audio line inputs (-28 dBm to -15 dBm),
set to Cl position.
c.
Set switch $2 on the Audio PWB to ON to activate the
audio AGC¯
do
Check that R6 on the Audio PWB is fully clock-wise. DO
NOT ADJUST R20 OR R44.
B.
Automatic Shutdown Adjustment:
Place the IDENT/CARRIER/CONT switch S1 on the AM Recycle
PWB in the CARRIER position.
Apply power to the transmitter.
Adjust RF power from the transmitter to the desired shutdown
level using RF Drive Control R39 on the AMOscillator PWB.
Place the transmitter meter function switch in the 25 DC
volts position and connect the test probe furnished with
the transmitter between the Probe Jack terminal next to
the meter and TP2 on the Autoshutdown PWB. See figure,
"Control and Testpoints Positions."
Rotate R6 and R22 located on the Autoshutdown PWB fully
CCW.
Rotate R6 CW until a downward deflection of the meter is
observed.
SS-800AVS
Southern Avionics
Company
105
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