DE
DANIELS
ELECTRONICS
3-2
VT-4R150 VHF Project 25 Digital Transmitter Instruction Manual
3.3
Major Frequency Change
Changes greater than ± 1 MHz from a previously tuned transmit frequency will require RF
Amplifier alignment as per the UHF Amplifier Instruction Manual. The Digital Transmitter Signal
Processor Board, once programmed for the new frequency, should not require any alignment, as it
is capable of operation over the entire band from 406-470 MHz.
3.4
Digital Signal Processor Board Alignment
If the Digital Signal Processor or Transceiver RF Boards have been replaced, it is necessary to
align the Digital Signal Processor Board. This consists of adjusting the reference oscillator
frequency, aligning the deviation balance at high and low modulation frequencies, and adjusting
the deviation limiting at a number of frequencies over the operational band of the Receiver.
3.4.1
Radio Service Software
The Radio Service Software is an application that runs under Microsoft Windows 3.1, 95, or 98,
and is used to program the radio’s channel frequencies and other operational characteristics. It is
used in conjunction with the Radio Programming Interface Module to read and write information to
the internal memory of the radio. For information about installing and using the Radio Service
Software, see the Radio Service Software Manual, which is available as an Adobe Acrobat file
(.PDF) on the CD-ROM, which contains the Radio Service Software.
3.4.2
Radio Programming Interface Module Interconnection
The Radio Programming Interface Module is used to make a connection between the computer
running the Radio Service Software and the radio module. On the computer side, it connects to an
RS-232 serial port via a standard nine pin serial cable. Another cable connects the Radio
Programming Interface Module to the radio to be programmed. Once the connections are made,
the Radio Service Software may be run on the computer and the radio switched on. The Radio
Service Software must be configured to use the correct serial port on the computer. This is done in
the Preferences menu of the Main screen. When the radio is switched on, the Power LED on the
Radio Programming Interface Module should light. To test the serial connection, open the
Receiver Configuration screen by clicking on the Transmitter button in the Main screen. Click on
the Receiver menu, then on the ID… menu item. Click on the Read ID button. The Data LED on
the Radio Programming Interface Module should light briefly and the serial number, model
number, and last programmed date should appear in the appropriate fields.
3.4.3
Reference Oscillator Adjustment
The reference oscillator provides an accurate frequency standard to which the transmitter's carrier
signal is phase locked. To adjust the reference oscillator frequency, disconnect the Transceiver RF
Board from the amplifier module by separating the SMB connectors. For this test, the Transceiver
RF board will generate a 0 dBm RF signal from its RF output. Connect the RF output cable of the
Transceiver RF board to a frequency counter or communications test set. Connect the transmitter
to an IBM compatible computer using the Programming Cable. Apply power to the transmitter and
run the Radio Programming Software. Navigate to the TRANSMITTER \ SERVICE \
REFERENCE OSCILLATOR menu, where you will see a test frequency displayed and a slider to
adjust the frequency. Click on the "ENABLE TX" button and move the slider until the frequency