Yaesu FT-901DM Maintenance Service Manual page 170

FILTER UNIT (PB-1995)
The IF signal received at pin 2 of the FILTER
UNIT (PB-1995) is amplified by parallel-connected
Q3o1 and Qjos (both 2SKI9GR), and fed through
a monolithic filter XF39, (8.9M-20A), which h
a +10 kHz bandwidth, providing additional sele
tivity and enough delay time to match the noise
blanker gating pulses. The signal is then fed to the
second IF amplifier, Q3o2 (2SKI9GR).
The noise blanker diode Do, (181007) is placed
between Ty392 and T4393, and it functions as an
ON/OFF switch which is controlled by the noise
blanker driver Q3o3 (2SCI8I5GR). The output
from the source of Qo) is passed through the SSB
filter XF39q (or the optional AM or CW filters).
Selection of the filter to be used is performed by
one of the diode switches D393 - D3os (181007).
depending on the mode of operation. The IF
signal is then transferred to the IF UNIT. In the
FM mode, the IF signal is coupled directly through
D319 (181555) to pin S of the IF UNIT.
Filter unit (PB-1995)
I
!
1
|
! pg-i995
[FILTER UNIT