Circuit Description - Yaesu FT-902DM Instruction Manual

CIRCUIT DESCRIPTION
This transceiver utilizes PLL (Phase Locked Loop)
'circuitry. The receiver is a single-conversion type
with a 8.9875 MHz IF. The following circuit des-
cription is tailored to the full-feature FT-902DM,
and some of the features and circuitry described
below are optional on the FT-902D/SD/DE
models.
RECEIVER
The RF input signal from the antenna is fed to pin
3 of the RF UNIT (PB-2154) via antenna relay
RL2, line fuse FH: ; attenuator switch S2103, input
transformer T; , and 9 MHz trap coil T2402.
RO.
12 pe
007 S53
RE UNIT (PB-2154)
The incoming signal is amplified by the RF ampli-
fier Qio1 (3SK51-03), a dual gate MOSFET which
has superior rejection against cross modulation.
The amplified signal is then fed to the first mixer
Qio2 (ND487C2-3R), a Schottky-barrier double-
balanced mixer, for excellent intercept character-
istics. The RF signal is mixed with a local signal
delivered from the LOCAL UNIT, resulting in a
8.9875 MHz first IF. The IF signal is then ampli-
fied by Qio3 (J310) and delivered to the FILTER
UNIT.
The input and output of the RF amplifier are
permeability tuned circuits, resulting in high
sensitivity with excellent rejection of unwanted
out-of-band signals.
|
Q02 ND487C2-3R Qo3 |
|
|
| 3 po,
| s{& x
Ss
| Be sle |
VSISS5X2 2 !
~jd
72 6 af Bes istes OFS |
| S is |
5
| &h Q06
| 8 3SK40M ees - ey oe
28C240 ne 3
| a ' R36 C33 SST oF & Ey |
Na GOS. 330 20487 R26 560 S| £26 120 «TSN aoa |
| ae NS < 138 & l
|
a Els
8
OS
. oy
28C2407
| S28 s 9 &) 407 3e0P RIF 560 |
5J8
S| 2047
e +
My
|.
as Shoe « |S Sa Sa gkG8 er 703
| N a g & 2 N ey | Ss bt 201 LOCAL
|
8
al
8
a s
ce
«
IN
| e 3 8 & ealsl x |
I
Rao 10
is
SSesz * <Q
1
Oo ~ Ki 7 > wt — ee ies © |
YAR oy eis Oy 9, se
3 FS EY 8 VS |
ofs Ste oe Ss]
; : |
mie
| STs |
| |
besa ett ee Dee oe i al oe ee ee