Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 111

CIRCUIT DESCRIPTION
WJ-8718-19/FE HF RECEIVER
3.4.6
2ND CONVERTER (FE-A1A2A2) (270907)
The 2nd Converter mounts on the Frequency Extender, FE-Al, Assemblv
(see paragraph 3.3.2). Figure 3-13 is a detailed block diagram of the 2nd Converter
which should be referred to in the following circuit description. Figure 6-9 2nd
Converter Schematic Diagram, may be referred to for greater component level detail if
d esir ed. '
The 159.5 MHz 1st IF signal from the 1st Converter is applied through an
impedance matching network to the input of mixer U3. The 189 MHz LO signal from
the 2nd LO Synthesizer is amplified to a level of +15 dBm by buffer U2 and applied to
mixer U3. U3 mixes these two signals to give a 2nd IF output of 29.5 MHz U2
output is amplified by 15 dB by buffer Ul and is sent as the FE IF output to RF
switch FE-A2.
3-28
MIXER,
U3
L
IF IN
»6
f
IF AMP
Ul
y;
•
{
LO AMP
U2
Figure 3-13. 2nd Converter, FE-A1A2A2, Block Diagram