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SWEEP TIMING ADJUSTMENT
This
adjustiiiGfit
is
carried.
out
to
proper
radar
performancci
especially on
short
ranfjes.
The radar measures the time required
for
å
transmitted
echo
travel
to
tho
target and
return
to
the
source,
and
the
received echo is displayed on tho C ElT based on this time.
Thus,
at the
tnsiant the iransinllter is lired, the "Sweop" should start from the center of
the CRT (sometimes called sweop origin.)
A
"trigger'' pulse
gonorated in the
Diaplay Unit
is
sent
to
the
Soaruier Unit
through
the interconnection
cable
to
trigger
the
transmitter
(magnetron.)
The
time
taken
by
the
signal
to
travel
up
to
the
Scanner
Unit
varies,
depending
largely
on
the
length
of
interconnection
cable.
During
this
period
the
Display Unit should
wait before starting the sweep.
When
the
Display
Unit
is
not
adjusted
correetly.
the
echoes
from
a
straight
local
object, e.g., a harbor wall,
straight pier, etc. 'will not appear with straight
edges
i.e.,
they
wiu
be
soen
as
"pushed ouf' or "puUed in"
near the
picture
center.
The
range
of
objeets
will
also
be
incorreetly
shown.
Therefore, the foUowing adjustinent should be carried out after installation.
Procedure
1. Set the unit at 0.25 nm range and adjust the GAIN and A/C SHA Controls
properly.
2. Visueily, select a straight object, e.g., a harbor wall, straight pier, etc.
3. Adjust
the
"TIMING"
potentiometer
(VR6.
Fig,19)
so
that
a
straight
object
will
appear
straight
with
no
"pushing"
or
"pulling"
near
the
picture center.
(A) irrproper.
(B) proper
(C) improper.
pulling inivard
pushing uutwBrU
Pig.14 Sweep Timing Adjustinent
PRESET GAIN ADJUSTMENT
Preset gain is preadjusted at the factory.
However if the receiver gain is
loo liigh or low, adjust it agaln.
Procedure
1.
Set the Controls:|giØ.±|: 24 nm;
GAIN:
fully CW (max-); A/C SEA: fully
CCW (min.);
:
off;
:
off;
:
off, and
: on.
2. Set VR4 at the position where a Kttle background
uoise appears oii the
screen.
See Fig.l9 for the location of VH4.
3. Conf^rifi
that
the
noise
inereases
when
the
Ilt
ciruuil
is
nol
aclivated.
(
touchpad:
OFF)
18
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