Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 92

WJ-8718-19/FE HF RECEIVER
3.3.
3.3.1
Main Chassis Regulator Outputs:
Ul:
+15 Vdc
U2: -15 Vdc
U3: +5 Vdc
Main Chassis Motherboard Outputs:
Ul:
+5 Vdc
U2: +5 Vdc
U3: +12 Vdc
FUNCTIONAL THEORY OF OPERATION
INPUT RF SWITCHING SECTION
CIRCUIT DESCRIPTION
Figure 3-2 is a block diagram of the Input RF Switching Section. As
shown in Figure 3-2, it consists of two major assemblies: Input Switch FE-A2, and RF
Filter, A2.
3.3.1.1
Input Switch FE-A2 (794276)
Input RF signals from 0-100 MHz enter the switch via Jl. When the
Switch Control line from Digital Control is low (receiver tuning from 0 to 29.9999
MHz), the signals pass through FE-A2 to J2; from J2 to J4; through FE-A2 to J5; from
J5 to RF Filter, A2. When the Switch control line from Digital Control is high
(receiver tuning from 30 to 99.99999 MHz), the signals pass through FE-A2 to J3; from
J3 to A1A1 of the Input Converter/2nd LO, FE-A1A1.
3.3.1.2
RF Filter (A2) (791616)
The RF Filter (A2) is a 15-pole low pass filter with a 50 ohm
characteristic impedance and a 3 dB nominal loss. RF input signals from the Input RF
Switching Section are band-limited to 5 kHz to 30 MHz by the RF Filter and are
applied to the Input Converter (A3).
3-9