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Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
I.B.1516A
Mar 30/01
23-12-01
Along with the reference signal, the phase comparator of the PLL is also supplied
with the down-converted frequency of VCO3. The mixing frequency for this down
conversion is obtained from a second PLL. The reference frequency of the 2nd PLL
is derived from a crystal oscillator (10Mhz), which is scaled down by a factor of 100.
The 1st IF of 40.025MHz is supplied to the 2nd mixer via a variable amplifier and
converted to the 2nd IF of 25kHz. The mixing frequency for this mixer (40MHz) is
also generated with the aid of a PLL, whose reference frequency (1MHz) is derived
from a crystal oscillator.
The 2nd IF signal (25kHz) is digitized by a 16-bit A/D converter and supplied to the
signal processor. The demodulation and conversion of the signal to an audio fre-
quency (AF) signal is executed in the signal processor.
The principal functions performed in the signal processor are:
• Demodulation (SSB, AM)
• IF filtering for audio, SELCAL, and AM
• Automatic gain control (90dB dynamic range)
• Squelch
• The audio signal is applied via D/A converter (sampling rate 12.5kHz)
to the audio, SELCAL, and data outputs
(b)
Transmit Mode
The audio signal (voice or data) is digitized by the 16-bit A/D converter (100kHz
sampling rate) and read into the signal processor.
The functions that are performed in the signal processor by means of software are:
• Filtering of the audio signal
• Voice compression
• Automatic level control
• Conversion to 25kHz IF frequency
• Conversion of SSB or AM(E) signal
• Mixing to 25kHz
The 25kHz IF signal thus created undergoes analog conversion in a D/A converter
(sampling rate 100kHz). The signal is finally converted to the frequency in the 2.0
to 29.9999MHz range.
The conversion oscillators are generated in the same way as for receive operation.
The output signal of Receiver/Exciter, A1, is a –7dBm (nominal) signal, which is
supplied to the Power Amplifier, A3.
The Receiver/Exciter module is connected to the Controller module, A8, via the
module bus, where all settings are made; e.g., frequency, operating mode, trans-
mission mode, BIT functions.
BIT results and the signal level can be determined via the module bus.
(2) Power Amplifier, A3
Power Amplifier, A3, is composed of Amplifier Board, A31, Harmonic Filter, A32, and Am-
plifier Control, A33. Refer to Fig. 8 for block diagram.
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