Yaesu FT-902DM, Instruction Manual

Page: 9 / 55

m inimum input level from the microphone to
trigger the m icrophone amplifier. L ow-level back­
gr ound noise w ill n o t activate the transmitter
w ith the AMGC in operation . This circuit m ay be
c onsidered a "microphone squelch " sy stem . The
M
GAIN c ontrol function s normally with the
AMGC sy stem in operation .
W hen the APF/MONI swi tch is in the APF p osi­
tion, the audio peak fil ter (APF ) circuitry
is activated . The exact frequency of the audio
peak i s set by the APF F REQ knob . W hen this
switch is placed in the M ONI p osition , m onitor­
ing of the m icrophone level m ay be accom plished
for op erator convenience or tape recording b oth
sides of a
QSO.
In the CW mode, CW sidetone
w ill be heard regardless o f the position of the
APF/MONI swi tch.
The A GC swit ch controls the length of the re­
c overy time for the re ceiver AGC circuitry . This
swi tch provides sl ow or fast recovery , and will
also turn off the AGC if desired.
The PO/ IC/ ALC switch will h ereafter be re ferred
to as the METER swrf ch . In the PO posi tion,
relative transmitter output power can be observed .
In the IC p osi tion , transmitter final am plifier1
c athode current m ay h e measured. In the A LC
p osition, transmitter A LC voltag e m ay be read.
W hen the F T- 9 02DM is in the receive m ode, the
me ter ftt ncti ons as an
"S"
m eter.
The NB/MARK switch provides for actu ation of
either the N oise Blanker (NB ) or cry stal calibrator
(MARK) . The marker oscillator can produce cali­
brati on sign als at intervals of either 25 kHz or
I
00 kH z by proper p ositi oning of a switch inside
the cab in e t.
( 2 2) POWER
This is the m ain on/off switch for the transceiver.
In the OFF position , the memory circuits are
disab le d , so that wh en the transceiver is turned to
O N again, the memory circuits will have to be
�
reset .
( 23) HEATER
W ith the H EATER swi tch in the down po sition ,
the transmi tter tube heaters are turned o ff. T his
reduces b attery , d rain to
I. I
amp and thus perm it s
long periods of listening with out excessive battery
d rain. Placing this switch in the up position pro­
v ides supply voltage t o the tube heaters, and
after 3 0 se cop ds of warmup t he transm i t ter is
re ady for operation . This swi tch operates in both
the AC and DC m odes.
( 2 4 ) P HONES
This is a s tandard I /
4"
phone j ack
for
accom­
m odation of headphones. The in ternal sp eaker is
disabled when headphones are plugged into this
jack.
( 2 5 )
MIC
This four-conductor j ack accom moda tes the
m icrophone plug for mi crophone input a s well as
for PTT actuation .
MIC
TI
PTT swi tch
2 Ml(
�/
3 PTT
4 N (
Mic
plug
Headphone plug
lJ i
:
i
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