Vertex Standard VX-4000L, Service Manual, Page: 25 / 80

5-4
VX-4000 VHF Low-band Service Manual
Alignment
CTCSS Modulation Level
r
Stay on the band center frequency channel, with
151.4 Hz CTCSS encode, and reduce the AF gen-
erator injection to zero.
r
Key the transmitter and adjust (by control com-
mands from the computer) for CTCSS deviation
of ±0.75 kHz (± 0.1 kHz) as indicated on the de-
viation meter.
DCS Modulation Level
r
Stay on the band center frequency channel, with
DCS 023 enabled, and leave the AF generator in-
jection at zero.
r
Key the transmitter and adjust (by control com-
mands from the computer) for DCS deviation of
±0.75 kHz (± 0.1 kHz) as indicated on the devia-
tion meter.
Receiver
The sensitivity parameters can be adjusted from
the computer by utilizing the Alignment Software.
Refer to the onboard help of the Alignment Software
Manual for details.
r
Set up the test equipment as shown for receiver
alignment, and install the audio test adapter.
r
With the transceiver set to the band center fre-
quency channel, and with the RF signal genera-
tor tuned to the same frequency, set the genera-
tor for ±3.0 kHz deviation (for 25 kHz steps) with
1 kHz tone modulation, and set the output level
for 1µV at the antenna jack.
r
Adjust (by control commands from the computer)
the receiver front-end tuning for optimum
SINAD, reducing signal generator output level
as necessary for proper meter deflection.
r
After the previous step, the final signal genera-
tor level should be less than –6 dBµ for 12dB
SINAD.
Squelch Threshold
The squelch parameters can also be adjusted from
the computer by utilizing the Alignment Software.
Refer to the onboard help of the Alignment Software
Manual for details.
r
Select the band center frequency channel, and
with the RF signal generator turned to the same
frequency, set the generator for ±3.0 kHz devia-
tion with 1 kHz tone modulation, and set the out-
put level for –7dBµ at the antenna jack.
r
Adjust the squelch threshold level (by control
commands from the computer) such that the
squelch just closes at this signal input level (the
BUSY LED will turn off).
50-Ohm
Dummy Load
RF Signal
Generator
Power Supply
13.8V DC
AF Generator
SINAD
Meter
AF Test
Adapter
AC Volt
Meter
Inline
Wattmeter
Deviation
Meter
RF Sampling
Coupler
CT-71
Connection
Cable
Frequency
Counter
Transceiver