Honeywell XK516D1 Maintenance Manual page 63

protection for the gate of V4. The operating point of transistor, V4, is set to permit a
drain current of ID = 100mA to flow.
Amplified by about 16dB, the RF signal is supplied via the series resistor R50 to the
voltage-controlled attenuator. The RF output level changes in relation to ALC volt-
age (X2.32) in such a way that the RF amplifier operates with constant output power
according to the set power level. The ALC control voltage is supplied via RC section
R65, C46 and resistor network R57, R66 to operational amplifier, N70-C. This am-
plifier has the task of coupling the control voltage to emitter follower V13, V28. The
emitter follower represents a low-resistance voltage source, which can be used to
obtain high control rates. PIN diodes, V3, V26, and V2, V27, are driven via resis-
tance branches, R58, R13, R12, R17, R18, which regulate the transmission signal.
Initially, PIN diodes, V2, V27, are active; with higher attenuation, control with PIN
diodes, V3, V26, takes effect. This offset of the initiation points improves the inter-
modulation behaviour.
Diodes, V14, V18, and V20 to V22, linearize the characteristic curves of the PIN di-
odes. L2, L5 and C13, L6, and C53, as well as L210, C200, C210, and C220 serve
as filter sections. C7, C45, L4, and C11, C54, L1 operate as equalizing low-pass fi
lters. To save leakage power when receiving, or to avoid flow through the PIN di-
odes, the + input is connected from operational amplifier, N70-C, to frame potential
via transistor, V23, depending upon the RCV 5.3V logic signal (X2.43).
The output signal of the PIN diode actuator is supplied via the matching network
composed of R69, C104, L12 to transformer, T1, and to the 2nd amplifier stage,
which has a similar setup to the 1st amplifier stage with transistor, V4. The RF signal
passes via series resistor, R70, and coupling capacitor, C102, to transistor, V9,
which is reverse coupled with C103, R75 in order to optimize the frequency re-
sponse. The drain/source voltage is supplied to transistor, V9, via filter section, L73,
C106. The gate/source voltage is set with potentiometer, R73, via voltage divider,
R103, R71, series choke, L206, and diode, V7.
Zener diode, V8, provides overvoltage protection for the gate of V9. The operating
point of transistor, V9, is set to permit a drain current of ID = 100mA to flow. The
amplification of the 2nd amplifier stage is also 36dB.
The RF signal passes via coupling capacitor C201 to parallel resistor R133 and fi-
nally to transformer, T6. The signal arrives at transistor, V39, which forms the
preamplifier, via coupling capacitor C79.
The transistor is reverse coupled with L10, R131 in order to optimize the frequency
response and for reasons of stability; C75 is used for direct voltage isolation. The
drain/source voltage of +28V is supplied via filter section, L11, C80, to transistor,
V39. The +28V supply voltage is also filtered by electrolytic capacitor C111.
The gate/source voltage is set with potentiometer R130 via voltage divider, R122,
R121, and series resistor, R132, or diode, V43. Zener diode V10 provides voltage
protection for the gate of V39. The gate/source voltage is derived from the +15V
supply voltage, as is the case with the first 2 amplifier stages. The operating point
of transistors, V39, is set to permit a drain current of ID = 1.0A to flow. The pream-
plifier has an amplification of about 22dB, whereby the ballast resistance formed by
the final stage amounts to about 5
1I.B.1516A
Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
Ω
23-12-01
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Page 54 Page 34
Mar 30/01