Service manual

17
Alignment
Using the CN-1N BNC Adapter
Receiver Alignment Points
Washer
P/N : R6148750
PANEL REAR
ASS'Y
Nut
CN-1A
Receiver
Set up the test equipment as shown for receiver align-
ment, and construct the audio test adapter as described
in the box on previous page .
The VX-520U uses a threaded-type antenna jack to
match the supplied helical flex antenna. To connect the
VX-520U to test equipment or an external coaxial-fed an-
tenna, the CN-1A adapter should be used to mate the trans-
ceiver with standard BNC connector.
With the transceiver assembled, the CN-1A adapter can
be installed by simply unscrewing the antenna, and in-
stalling the CN-1A in its place. When performing the align-
ment procedure, first disassemble the transceiver case as
described, then replace the washer and threaded nut re-
moved from antenna jack. Install the CN-1A adapter by
carefully threading the unit on the antenna jack nut, then
rotating the black knurled collar clockwise until it is fin-
ger-tight.
To ensure a sufficient RF ground at the antenna con-
nector during the alignment procedure and when mak-
ing measurements, install the ground plate by sliding it
over the CN-1A connector and then insert and tighten the
supplied M2.6 x 3 screw into the rear case (see illustra-
tion).
Remember to remove the nut and washer again before as-
sembling the transceiver body halves.
CV3201
CV3202
Ë With the transceiver set to band center CH 2, and the
RF signal generator tuned to the same frequency, set
the generator for ± 3.0 kHz deviation with 1 kHz tone
modulation, and set the output level for 40 µV at the
antenna jack.
Ë Adjust CV3201 and CV3202 on the Main Unit for opti-
mum SINAD, reducing the signal generator output level
as necessary for proper meter deflection.
Ë After the previous step, final signal generator level should
be better than –4 dBµ for 12 dB SINAD.
ANT
RF Signal
Generator
AF Test
Adapter
AC Voltmeter
Regulated DC
7.2V PSU
SINAD Meter
Speaker
or 8-ohm load resistor
EAR
Receiver Alignment Setup
Squelch Threshold
Ë Set the transceiver to CH 2, and turn off the RF signal
generator output.
Ë Turn VR4002 on the VR Unit clockwise until the squelch
just closes, and then counter-clockwise very slightly so
that it just opens.