DRS WJ-8611, Инструкция по установке, эксплуатации и обслуживанию

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WJ-8611 DIGITAL VHF/UHF RECEIVER
CIRCUIT DESCRIPTIONS 5-7
Table 5-2. 1st LO Synthesizer Tuning Bands
Band Tuned Frequency Range 1st LO Frequency Range
Switching Test
Point
1 20.0000 - 192.5000 MHz 1370.0 - 1542.5 MHz TP 13
2 195.0000 - 400.0000 MHz 1545.0 - 1750.0 MHz TP 12
3 402.5000 - 610.0000 MHz 1752.5 - 1960.0 MHz TP 11
4 Not Used TP 14
5 612.5000 - 822.5000 MHz 1962.5 - 2172.5 MHz TP 16
6 825.0000 - 1000.0000 MHz 2175.0 - 2350.0 MHz TP 15
The frequency of the 1st LO synthesizer is controlled by a tuning voltage
produced by the synthesizer’s phase detector. It is the result of comparing
a frequency divided sample of the VCO output frequency with a fixed
reference. The 10 MHz reference signal entering the assembly at terminal
E2 is divided by a factor of eight to produce a 1.25 MHz square wave at
the phase detector reference input (TP23). When the synthesizer is locked
on frequency, the
÷
N and
÷
A counters divide the VCO frequency sample
down to equal the reference frequency. This is visible at TP4 as a series of
voltage spikes at a 1.25 MHz rate. The results of this frequency
comparison produce the tuning voltage. At TP24, the tuning voltage will
range from approxi1.5 to +16 V, depending on where in the active
VCO band the oscillator is tuned. If the synthesizer fails to lock on
frequency, this voltage will swing to its minimum or maximum extreme
(0 V or +22V).
The operating power for the 1st LO/1st Converter PC Assembly (A3A1) is
supplied through connector P1 from the 2nd LO/2nd Converter PC
Assembly (A3A2). The input voltages are +5.5 Vdc at pins 2 and 3,
+24 Vdc at pin 4, +13 Vdc at pin 6, and -13 Vdc at pin 7. These voltages
are routed through regulation circuitry in the assembly and are distributed
to the various circuits in the assembly.
5.2.2 PART 482903-1 2ND LO/2ND CONVERTER PC ASSEMBLY (A3A2)
The functional block diagram of the 2nd LO /2nd Converter PC Assembly
(A3A2) is illustrated in
Foldout FO-5 . Refer to this illustration for the
following module description.
The 2nd LO/2nd Converter PC Assembly (A3A2) accepts the 1350 MHz
IF from the 1st LO/1st Converter PC Assembly (A3A1) and performs the
2nd and 3rd stages of signal conversion to produce two IF outputs. The
wideband 21.4 MHz Signal Monitor Output (J2) supplies a 50-ohm output
to the rear panel for use with an external signal monitor or spectrum
display unit. Its level is approximately 14 dB greater than the receiver’s
RF input level. The 250 kHz IF output (P1) provides a 200 kHz wide IF
signal to the Digital Control PC Assembly (A2) to be digitized prior to
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