Codan Radio Communications VT-4-150 User Manual
DE
DANIELS
ELECTRONICS
3-4
VT-4R150 VHF Project 25 Digital Transmitter Instruction Manual
the transmitter should be connected to a service monitor set to monitor the deviation of the carrier
signal generated by the transmitter. Key the transmitter by moving the front panel power switch to
the “KEY” position and adjust pot R11 to achieve a deviation of 3 kHz (for a 25 kHz wide
channel) or 1.5 kHz (for a 12.5 kHz wide channel).
Next, de-key the transmitter and remove the audio signal generator. Connect the signal generator
to microphone connector MIC1-2. Key the transmitter by moving the front panel power switch to
the “KEY” position. Adjust pot R9 to achieve a deviation of 3 kHz kHz (for a 25 kHz wide
channel) or 1.5 kHz (for a 12.5 kHz wide channel). This completes the audio level alignment
procedure.
signal generated by the transmitter. Key the transmitter by moving the front panel power switch to
the “KEY” position and adjust pot R11 to achieve a deviation of 3 kHz (for a 25 kHz wide
channel) or 1.5 kHz (for a 12.5 kHz wide channel).
Next, de-key the transmitter and remove the audio signal generator. Connect the signal generator
to microphone connector MIC1-2. Key the transmitter by moving the front panel power switch to
the “KEY” position. Adjust pot R9 to achieve a deviation of 3 kHz kHz (for a 25 kHz wide
channel) or 1.5 kHz (for a 12.5 kHz wide channel). This completes the audio level alignment
procedure.
3.4.7
Amplifier Alignment
The RF power output of the amplifier is set to its rated value of 2.0 Watts or 8.0 Watts at the
factory. This should not require adjustment under normal circumstances. However, should it be
necessary to correct the output power, the 'Output Power Adjustment’, which is described in the
Amplifier Manual, can be adjusted accordingly. Power adjustment may also be required when the
transmitter's operating frequency is changed. When a large frequency change has been
programmed into the transmitter, the amplifier should be aligned at the new frequency according to
the Amplifier Manual.
factory. This should not require adjustment under normal circumstances. However, should it be
necessary to correct the output power, the 'Output Power Adjustment’, which is described in the
Amplifier Manual, can be adjusted accordingly. Power adjustment may also be required when the
transmitter's operating frequency is changed. When a large frequency change has been
programmed into the transmitter, the amplifier should be aligned at the new frequency according to
the Amplifier Manual.
3.5
Recommended Test Equipment List
Alignment of the transmitter requires the following test equipment or its equivalent.
Dual Power Supply:
Regulated +9.5 Vdc at 2 A.
Regulated +13.8 Vdc at 2 A - Topward TPS-4000
Regulated +13.8 Vdc at 2 A - Topward TPS-4000
Oscilloscope / Multimeter:
Fluke 97 Scopemeter
Current Meter:
Fluke 75 multimeter
Radio communications test set:
Marconi Instruments 2955R (analog only)
Motorola R2670 with Project 25 option
Motorola R2670 with Project 25 option
Alignment Tool:
Johanson 4192
It is recommended that the radio communications test set be frequency locked to an external
reference (WWVH, GPS, Loran C) so that the high stability oscillator may be accurately set to
within its ±1 ppm frequency tolerance.
reference (WWVH, GPS, Loran C) so that the high stability oscillator may be accurately set to
within its ±1 ppm frequency tolerance.
3.6
Repair Note
The transmitter is mainly made up of surface mount devices, which should not be removed or
replaced using an ordinary soldering iron. Removal and replacement of surface mount
components should be performed only with specifically designed surface mount rework and repair
stations complete with ElectroStatic Discharge (ESD) protection.
replaced using an ordinary soldering iron. Removal and replacement of surface mount
components should be performed only with specifically designed surface mount rework and repair
stations complete with ElectroStatic Discharge (ESD) protection.
When removing Surface Mount Solder Jumpers, it is recommended to use solder braid in place of
manual vacuum type desoldering tools when removing jumpers. This will help prevent damage to
the circuit boards.
manual vacuum type desoldering tools when removing jumpers. This will help prevent damage to
the circuit boards.