Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
1I.B.1516A Page 28
Mar 30/01
23-12-01
Synchronous demodulator, with which the frequency of the signal is converted
in such a way that the carrier obtains a frequency of zero. A digital phase-locked
loop (DPLL) ensures that the phase of the demodulated signal also remains
constant within a channel width.
A squelch function can also be connected as an option. If the level of the carrier
exceeds the set 16-stage threshold, the demodulated AM signal is connected
through to the audio output.
The squelch function is not available in the DATA mode.
5
SELCAL Reception
SELCAL output is effected by means of D/A converter, D8, LF amplifiers, N4-A,
and D and anti-aliasing filter N4-B, and C. This filter suppresses higher spectral
elements arising as a result of the scanning frequency of 12.5kHz. SELCAL re-
ceive mode corresponds to AM reception as described above with 2 exceptions:
a. The demodulated AM signal appears at a separate output.
b. A squelch function cannot be activated, with the result that a signal is always
present at the SRA output.
(c)
Transmission Section
The modulation signals for Receiver/Exciter, A1, can be applied at either the DATA
or microphone input. They are digitized and processed in the signal processor.
There, the signal is output as the 1st IF of 25kHz, before subsequent conversion to
40.025MHz.
After the second conversion stage, a –7dBm RF signal in the range from
2.0000MHz to 29.9999MHz is present at the output of Receiver/Exciter, A1, either
as AME or USB/LSB.
In this connection, see the block diagrams Figs. 15 and 16.
1
IF Processor, A12
In the VOICE mode, the LF signals pass through symmetrical amplifier N5-D,
whose input impedance is determined by R293. This stage is used to amplify
the microphone voltage and to suppress common-mode interference (e.g. hum
voltages). The data input (DATIN) is an unsymmetrical 600
Ω
input (R294).
The level at both inputs can vary between –10 and +16dBm. The signal paths
are combined via switch S5-B and amplified in LF amplifier, N3-B. Switch, V710,
supplies the signal obtained in this way to amplifier stage N3-A and then to A/D
converter, D9, where it is digitized before finally being supplied to signal proces-
sor A12D1 (Ref. paragraph 4C(1)(b)2).
2
Functional Description SSB Transmission Mode
Selection stage with 2 different bandwidths, depending upon the operating
mode (DATA/VOICE). The linear phase (FIR) filters are without delay distortion.
Automatic gain control (AGC) stage, composed of a level range of 22dB. The
dynamic behavior of the control (hold, up, and down times) does not vary in the
DATA and VOICE modes and corresponds to the VOICE times for reception.
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