Direct Digital Synthesis - Codan NGT 2010 RF Technical & Service Manual

NGT—Technical description (2010)

Direct digital synthesis

Local oscillator for upper sideband and lower sideband
Drawing
ALTERNATIVE TEXT
IC404 divides the reference oscillator frequency of 44.545 MHz down to the required
456.5 kHz for USB and 453.5 kHz for LSB. These frequencies may vary when different
optional filters are used.
The frequency information is programmed serially from the on-board microprocessor
IC405.
Drawing
ALTERNATIVE TEXT
NOTE
IC405 and IC407 divide the reference oscillator frequency of 14.848333 MHz down to
the required 456.5 kHz for USB and 453.5 kHz for LSB. These frequencies may vary
when different optional filters are used.
The frequency information is programmed serially from the on-board microprocessor
IC408.
Phase lock loop reference
Drawing
ALTERNATIVE TEXT
IC403 divides the reference oscillator down to approximately 5 MHz. The signal is
buffered by V411 and is then fed as the reference frequency to IC401.
The reference frequency is varied in small step sizes to produce the 10 Hz steps at the
output of the phase lock loop.
The frequency information is programmed serially from the microprocessor IC405,
based on the channel information.
Drawing
ALTERNATIVE TEXT
NOTE
IC403 divides the reference oscillator down to approximately 5 MHz. The signal is
buffered by V411 and is then fed as the reference frequency to IC401.
The reference frequency is varied in small step sizes to produce the 10 Hz steps at the
output of the phase lock loop.
The frequency information is programmed serially from the microprocessor IC408,
based on the channel information.
94
04-03106 (sheet 3)
04-03378 (sheet 3)
If the PCB issue status is -06 or earlier, see drawing
04-03106 (sheet 3)
04-03378 (sheet 3)
If the PCB issue status is -06 or earlier, see drawing
04-03378 (sheet
04-03378 (sheet
NGT Transceiver System Technical Service Manual
3).
3).