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H 52382-900A
Vol.
1
para.
32
(continued)
Ex
ternal
s
tandard input
I
EXT STD
I
Input
connector
Reference frequency
FULL
SP^
LOG
I
I
ZERO
span]
,
I
'i^terI
&
FM DEMODi
I
sYg track
System will automatically
switch
to
an
external
standard
if a
signal of 1,2,5 or
10
MHz
is
applied
at a
level
of
between
-15 dBm and
+15
dBm.
The
frequency must
be
within
±1
part
in
10^
for the system
to lock.
The annotation EXT
STD
is
shown
on the
display when lock
is
achieved.
50
n BNC female.
A
dashed vertical
line may
be
moved across
the
display
by
operation
of the
keypad, REF FREQ
rotary control
or ++ keys.
The frequency
of
any
signal on
the
display
can
be read to
a
resolution
of
better than
1
MHz.
This facility
permits
signal selection made
in
this
mode
to be
displayed
at
the reference frequency
in
any
subsequent /DIV selection.
Reference frequency can
be
positioned
at
the
centre,
left hand or right hand side
of the
display
by
operation
of the
HORIZ POSN
key, the
appropriate
vertical graticule
line being dashed
to
indicate this state.
The value
of
the
reference frequency
can be read from
the
screen
annotation
to a
resolution
of
t0«2!S:
of
span
and
to
an
accuracy
of
±{(Freq.
std.
error
x
Ref.
freq./lO
MKz)
+2Z
of
selected sweep span
+
oscillator
drift]
Hz.
See ''Stability" for
oscillator drift figures.
This mode
is
also
selected
by
operation
of the
PRESET
key.
The
reference frequency rotary control
is
inoperative
in this mode*
Frequency accuracy
as
for /DIV mode but
no
allow-
ance
is
needed
for
oscillator
drift.
A
signal
at
the
reference frequency
of
the
display
is
tracked.
The tuning
of the
instrument
is
adjusted after every
sweep
to
cancel
out any
drift in the
signal being analyzed.
The only
restrictions
are that the signal must
be
positioned sufficiently
far up the
skirt
of the
response
to
ensure capture
and
that the signal
drift
is
not so fast that the
response drifts
off
the
display
in
one sweep interval.
Operates only
in HORIZ POSN centre mode.
If
the frequency span
is
rapidly reduced
a
single
sweep will
be
taken
at
appropriate Intermediate
values
so as not to lose track of the signal.
Chap.
1
page
10
July
85
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