Specifications

AE/LZB 119 1641 R1B
16
the proper device. The main synthesizer can be
programmed in 12.5 kHz steps. These inputs can be
metered at TP205 (CLOCK), TP206 (DATA) and TP207
(STROBE 1).
Bilateral Switch (N201)
Bilateral Switch N201 selects the loop filter required
for programming the main VCO in 12.5 kHz steps. A +5
Volt signal (LOOP_SEL) from HILLARY connects to
N201, Pin 5 (2_C
Control
) causing N201 to switch in the
required resistor-capacitor combinations. The selected loop
connects to the VCO at U200, Pin 2 (Vcont).
Main Voltage Controlled Oscillator (U200)
A signal from HILLARY (VCO_BAND_1) turns
transistor V201 on or off to select the band over which the
VCO will operate. The collector output of V201 connects to
U200, Pin 10 (SW). The output of U200 on Pin 8 (Output)
connects through buffer transistor V200 to the RX_ LO
through coupling capacitor C208. The TX_LO is taken
from the voltage divider consisting of resistors R203 and
R205. The feedback for the synthesizer circuit is taken from
the voltage divider consisting of resistors R202 and R204
and can be metered at test point TP202. The level of this
signal is typically 25 mV RMS. This feedback signal
connects through coupling capacitor C207 to N203, Pin 5
(INM1). The voltage level at this point is typically 4.5 V.
Main Synthesizer (N203)
In synthesizer N203 the feedback signal from the VCO
is input to a prescaler where it is divided down to produce a
19.2 MHz signal. This signal is compared with the 19.2
MHz reference frequency generated by reference oscillator
U201. When these two signals are equal, a lock voltage is
connected through N203, Pin 13 (PHI) or Pin 14 (PHP) to
the selected loop filter, locking the circuit to the output
frequency.
Auxiliary Synthesizer (N203)
The VCO in DIANE oscillates at the 2nd LO frequency
of 88.95 MHz. A +12 dB (100 mV RMS) feedback signal is
returned to N203, Pin 10 (INA). This signal can be metered
at test point TP208. A prescaler circuit divides this signal
down to 19.2 MHz. This signal is compared to the 19.2
MHz reference frequency generated by U201. When these
two signals are equal, a lock voltage is connected through
N203, Pin 11 (PHA) to DIANE through a filter circuit
consisting of resistors R225 and R226 and capacitors C217
through C219. This voltage can be metered at test point
TP209 and is typically 1-4 volts. This lock voltage locks the
2nd LO on frequency.
Reference Oscillator (U201)
Reference Oscillator U201 provides a reference
frequency of 19.2 MHz at 1.5 PPM for the Phase-Lock-
Loop circuit in the JACQUI module (the main synthesizer
for the receiver 1st LO, HILLARY and ATTIE). The output
level of this module is +16 dBM and can be metered at test
point TP204. The output of U201, Pin 3 (Output) connects
through a band-pass filter consisting of capacitor C235,
inductor L202 and capacitor C236. This output then
connects to the JACQUI circuit through the REF_OSC line
and to Frequency Synthesizer N203, Pin 8 (INR) through
coupling capacitor C223. The voltage level on Pin 8 is
typically 330 mV. A buffered output from JACQUI on Pin
19, drives the clock input of HILLARY and ATTIE. An
Automatic Frequency Control (AFC) line from ATTIE
(DAC03) provides a control voltage ranging typically from
0.5 volts to 4.5 volts to maintain oscillator integrity. This
DC level adjusts the reference oscillator frequency and is set
by tracking data. Filtering of this line is provided by
capacitors C222 and C234. Supply voltage for U201 is
supplied by synthesizer regulator N290 through the VSYN
line. This voltage connects through resistor R218 to U201,
Pin 4 (Vcc) and is filtered by capacitors C220 and C221.
DC POWER DISTRIBUTION
Battery voltage (7.2 Volts) connects to battery
connector X101, the positive terminal (BATT +) Pin 1 and
the negative terminal (BATT -) Pin 3. Fuse F190 and diode
V190 provide short circuit and reverse polarity protection.
If the battery terminals were connected incorrectly (positive
to negative and negative to positive), V190 would conduct
and fuse F190 would blow.
Synthesizer Regulator (N290)
Battery voltage connects through a decoupling circuit
consisting of inductor L290 and capacitor C290 to voltage
regulator N290, Pin 6 (Vin). A PWR ENABLE_B line,
originating from Power Switch V905, connects to N290, Pin
1 (Cntrl). When the Cntrl input is low, N290 is enabled and
a regulated 5.5 Volts is on N290, Pin 4 (Vout). Filtering for
this line is provided by capacitor C291. This voltage can be
metered at test point TP290 and becomes the VSYN line
going to the synthesizer circuit.
Receiver Regulator (N490)
Battery voltage connects through a decoupling circuit
consisting of inductor L490 and capacitor C490 to receiver
voltage regulator N490, Pin 6 (Vin). A RX_ON signal,
generated by D701, connects through enabling switch
transistor V490 to N490, Pin 1 (Cntrl). Resistor R290
connected to the base of transistor V490 is the pull-up