Daniels Electronics OSR-3H061, Инструкция по эксплуатации

Страница: 45 / 94

IM10-OS3AH
128-174 MHz - Synthesizer Alignment
41
Synthesizer Removal and Installation
Note: Complete synthesizer alignment
can be performed without removing the
synthesizer
The synthesizer module is secured to the main
board (MT-3 Receiver IF/Audio Board or MT-3
Transmitter Main board) with a single counter
sunk Phillips machine screw accessible from
the top cover. Remove this screw to remove
the synthesizer module. Using a plastic coated
lifting tool, such as a small screwdriver with the
tip covered in heat shrink material, gently lift the
synthesizer module from the main circuit board
by applying pressure in a rotating fashion about
the four corners of the synthesizer module. It
is important to gently remove the synthesizer
module “straight out” in order to prevent
damage to the connector pins. Installation
of the synthesizer is performed in a reverse
fashion. It is important to ensure complete
connector pin alignment prior to any application
of reinsertion force. Four corner locating pins
on the synthesizer housing assist in connector
pin alignment during installation and removal.
Circuit Board Removal
Note: Circuit board removal is not required
for tuning purposes.
Using a vacuum de-soldering station, de-
solder connections P1, P2 and P3. Remove
SMB connectors J1 and J2 by de-soldering
the center pins and removing four M2 machine
screws. These connection points are shown
in the Analog Board Component Layout
diagrams. Remove seven M2 machine screws
and carefully remove the analog circuit board.
Removal of the analog circuit board will expose
three inter-board wire connections. Carefully
remove three ferrite beads and six Tefl on
washers from the inter-board connection
wires. Attempt to maintain the position of the
three inter-board wires in order to simplify
re-assembly. The digital board may now be
extracted by removing four M2 machine screws.
Follow a reverse procedure to re-assemble.
Frequency Adjustment and Channel
Selection
Connect a radio communications test set
through a short section of low loss 50Ω coaxial
cable to the synthesizer module SMB RF
output jack (J2). Select the desired channel
code number via the BCD frequency selection
switches on the MT-3 Transmitter Main board or
the MT-3 Receiver IF/Audio board (or through
.the Frequency Programming Module). Turn the
power off and back on and wait a few minutes
for the oscillator to completely stabilize. It should
be noted that the internal synthesizer TCXO, if
installed, operates continuously (regardless of
the TX PTT state) when installed in a transmitter.
The measured RF output signal should be within
±1.0 ppm of the specifi ed oscillator frequency
at an output level of +5dBm ±2dBm at 25°C.
Note that unlocked synthesizer operation will be
indicated by an unstable or spurious RF output
signal. The “Unlocked” red LED will also be
illuminated when the PLL is unlocked. Check
that the requested channel number is within the
frequency range of the particular synthesizer
model. An unlocked condition may be rectifi ed
by adjusting the VCO tuning elements as
described in the following procedures.
VCO Alignment
Refer to the ‘Analog Board Component
Layout’ diagrams and the ‘Analog Board
Schematic Diagram’ in this section.
1) Measure the PLL DC control voltage at TP4
located on the synthesizer module analog
board (top) using a high impedence (10MΩ)
voltmeter (access to TP4 is available through
the synthesizer top cover).
2) Carefully adjust the VCO fi ne frequency
“TUNE” trimmer capacitor C24, using a
small standard blade screwdriver, until a
test point (TP4) voltage of approximately
+2.3VDC is obtained. PLL loop control
voltages below approxi0.5VDC and
above approximately +4.5VDC will indicate
an “out of lock” synthesizer condition.