Transceiver Location; Antenna Considerations; Grounding; Adjusting The Front Feet - Yaesu FT-990 Operating Manual
Yaesu ft-990 transceiver operating manual
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- Service manual (348 pages) ,
- Operating manual (65 pages) ,
- Manual (6 pages)
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Station-Installation
Trattsceiver Location
To assure
long
.life of the c:omponents, a primary
consideration in setting up the Fr-990
is
providing
for adequate ventilation arolll1d
the
cabinet. The
cooling system of the Fr-990 must be free to draw
cool air in
at the bottom rear of the transceiver, and
to
expel warm air
out
of
the upper rear panel. Do
not place the transceiver on top of another heat·
generating
devi~e
suth as
a linear
amplifi-er,
and
do not place equipment, books or papers
on top
of
the ttansceiver. Place the transceiver
on
a
h~rd,
flat
surface. Also
1
provide a few centimeters
of space
on
either
side
of the transceiver, if possible. Avoid
heating vents and wi11dow
locaUons that
could
expose the
transceiver
to excessive direct sunlight,
especially
in hcit climates.
Grounding
For protection from
shock
and proper
perform·
a
nee,
connect
the
GNO
terminal on the rear panel
to
a good earth ground, using a heavy
braiM.
d cable
of the shortest length possible.
All
other station
equipment
should
be.
connected to
the same
grounding cable, as close together as practical.
1f
you use
a
computer
with or
near
the
t-r-990, you
may
need
to
experiment with grounding of both
the lranscei"ver
and
the computer to
suppress
com-
puter
noise
in
the receiver.
Adjustittg the Front
Feet
The two
front
feet of
the
flr:990
can be
set in
eiU1erof
two positions. By turning
the-knurled
ring
around
a
(retr~cted)
.foot clockwise, the middle of
the foot will extend about one centimettY.
'TUrn the
ring as far
115
it will
gd
(abOut
1
1.1-turn) to lock the
extended
foot
in place.
To
retract an
extende.
d foot,
tum the knurled
ring
courtterclockw~e ~-tum
while pressing on the center of
the
.foot.
Adjusting
the Front
Feet
Anten11a Considerations
Any
antennas.connected to
the Ff-99.0
should
have
coaxial
feedlines
with
50-0
impedance,
rurd
include well,grounded lightning arrestors. for the
antenna at
the-main
ANT
ja·
c k, the
antenna tuner in
the
fT-990
is capable of matching aJltennas with an
SWR of
up
ro
3:1
or more on the amateur bands to
the
transmill'er.
Nevertheless, optimum perform-
.
ance for
both
reception
and
transmission will
gen-
erally
result with an antenna designed to provide
a
50-12
unbal;1nced
resistive
load at U1e
operating
frequency.
An anteM.a
that
is
not rE!Sonant
at
the
oper.aling frequency may present too high an
SWR
for proper
matching
with the built-in
antenna
tuner,
in
which
ca~e
·
the
antem1a
itself s hould
be
readjusted, or
an
outboard antenna tuner used. If
the
tuner
is
unable to
bring the
SWR
down
to
an
acc;eptable leVel, attempting
to
tra·nsmitwill
result
in
a.n
automatic reduction in power ou"tput
and
increased losses in the feedJine. Opera.tion lll1der
s
uch
conditions is
not recommended:
it
is better
to
install
another antenna designed
for·
that
band.
Also,
ifyour
;lritenna has
a
balanced feedpoint
and
vou ltse a balanced
feedline;
install
a
balun be-
tween
the feed
line
and
the.
transceiver's
.
A NT
jack.
The same
precau
tions.
apply to any
additional
(receive-only)
antenna
connected to U.1e.
RX
ANT
IN
jack,
except
that this
ru1t·
e nna
will
not have
the
bei)_efit
of
the
built-in antenna
tu~.
Therefore,
lm\ess
.such
a
receive-onJy ·antenna
has an
imped-
·ance near
50
n
a
t
the
operating frequency,
you
may need \11\.extt>mal tu.ner
for
good performance.
Interco.nttecfion
of
Acces~>ories
The
diag.rams
on
the·
following pages show in·
tercrimiediqllS
of
external
accessor!es. li you have
any questions on
tbe$e
accessories or connecting
devices nol shown, contact your dealer for advice:
Memory Backup
The lithium memory
BACKUP
switch
inside the
top
access
panel
Js
turiled on at the factory, allow-
ing
vfo and memory data
to
be retained while
power
is off.
Backup current
Js
miniscule,_
so it
is
not
necessary to tum
the
BACKUP
switch off
unless
U1e transceiver is to
be
s tored for
·
a
long.
time.
After
about five years
the transceiver
may fail
to
retain
memories (although
operation
will be other-
wiSe
unaffecte<l), and
the
lithium
battery
should
be
replaced. Ask your deal.er for replacement of the
battery,
or for
instructions
on
how
to
do so your-
self.
page6
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