Yaesu FT-902DM, Instruction Manual

Page: 15 / 55

OPERATION
The tuning procedure for this transceiver is not
complicated . However, care should be exercised
when tuning so that peak performanc e of the
equipment is secured . The following paragraphs
describe the procedure for receiver and transmitter
operation .
INITIAL CHECK
Before connecting the transceiver to a power
source, carefully examine the unit for any visib le
damage . Check that all modules are firmly in
place and that the controls a nd switches are op­
erati ng normally. M ake sure that the voltage spe­
cification marked on the rear p anel matches your
su
p
ply voltage, and that the line fuse on the rear
panel matches the supply voltage ; for 1 1 7 VAC ,
use a 5 amp fuse, and for 2 2 0 V AC use a 3 amp
fuse. For D C operation a fuse holder is installed
in the DC cable, and a 2 0 amp fuse should be
installed here.
FREQUENCY SELECTION
Freque ncy readout for the FT-902DM includes
both analog and digital readout. The analog read­
out dial shows calibrati on s at the
I
00 kHz and
I
0 kHz p oints, and is m arked , as well, in
I
kHz
increments for fine tuning. The digital read out
displays all digit s o f the operating frequency , with
resolution d own to 1 00 Hz accuracy.
RECEIVE OPERATION
( 1 ) Pr eset the controls and switches as indicated :
POWER . . . . . . OFF
HEATER . . . . . OFF
VFO . . . . . . . . Switch depressed
VOX GAIN . . . PTT position
RF GAIN . . . . Fully clockwise
AF GAIN . . . . Adjust sub sequently for com-
fortable level
BAN D . . . . . . . Desired b and
MODE . . . . . . . Desired mode
PRESELECT . . Desired ba nd segmen t
( 2 ) Turn the POWER switch t o ON . Th e meter
will light up and the operating frequency
will be displayed on the dial window . Adjust
the AF GAIN control for a com fortable
listening level, and adjust the PRESELECT
contra.I for maximum receiver noise or signal
level. The PRESELECT control may require
repeaking a s t he main tuning dial is tuned
across the b and.
( 3 ) The RX CLARI FIER may be utilize d if the
received signal is drifting. Pushing the RX
button and rotati ng the CLARIFIER control
will provide a means o f o ffsetting the receiver
frequency ±2. 5 kHz without changing the
transmitting frequency. A red LED indicator
will light up when the CLARIFIER is in use .
(4) When pulse-type n oise is encountered, the
NB (Noise Blanker) switch should b e acti­
vated, p roviding effective suppre ssion o f
this type of noise .
( 5 ) Rej ection of adjacent-channel interference
may be accomplished by several means. The
REJ ECT control may b e u tilized to place a
steep-skirt 3 0 dB notch attenuation on any
interfering signal within the IF p assband.
The WI DTH control varies the center fre­
quency o f one of two I F filters (the other
is fixed and presents a b oundary for narrow­
ing the p assband). Varying the WIDTH c on­
trol varies the IF selectivity fr om approxi­
mately 3 00 Hz to 2.4 kHz
· (at 2.4 kHz the
WID TH c ontrol is at
"O"
and the two filters
have the same center frequency) . Clockwise
rotation from the center (" 0"}
·
position
makes the passband n arrow toward the high
frequency side , while counter-clockwise ro­
tation n arrows th e p assband on· the low­
frequency side.
( 6 ) For CW reception , the APF (Audio Peak
Filter) m ay be activated . This fi l ter has a
1 0 0 H z peak b andwidth with very steep
skirts so as to provid e single-signal rec eption
for CW, with insertion loss o f less than
I
dB
when th e APF control is tuned exac tly to
the signal frequency. The APF F REQ control
varies the peak frequency from approximately
400 Hz to 900 Hz. The operator will observ e
that the APF system provides a signifi can t
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