HP 8340b User Manual

3.
Use
the
step keys to set
the
90
dB
attenuator,
and
the
data
entry
keyboard,
or
the
front
panel
knob,
set
the
MOD
(linear
modulator):
a.
Set
MOD
entry
at
0
dBm.
b.
Increment
the
ATN
until
the
POWER
dBm
display
shows
a
level
of
5
to
15
dB
higher
than
the
desired
output
power.
c.
Reduce
the
power
to
the
desired
level
by
changing
the
MOD
value.
Because
the
actual
power
changes
very
little
as
the
pulse
width
is
narrowed, even
though the
POWER
dBm
reading
drops,
at
very narrow
pulse
widths
ignore
this
reading.
The
ATN
and
MOD
values
in
the
ENTRY
DISPLAY
also have
a
limitation:
Although
the
ATN
displayed
value
is
always
accurate,
MOD
becomes
saturated
in
the
top
10
dB
(approximately)
of
its
range.
At this
point no change
occurs
in
the
true
power.
Because
of this,
rely
on
the
POWER
dBm
display for
the
true
power
level
instead
of the
MOD
value.
SHIFT METER
can
also
be
used
as
a
diagnostic function
of
the
ALC
circuits.
SHIFT
PEAK
(HP-IB:
SHRP)
This is
a
more
extensive version
of
peaking.
PEAK,
which
requires
a
fraction
of
a
second
to
imple¬
ment,
aligns
the
output
filter with
a
single
CW
frequency;
SHIFT
PEAK
aligns
all
of
the YTM
tracking
calibration
constants
and
requires
5
to
10
seconds
to
implement.
Use
SHIFT PEAK
to
enhance
the
power
output
and
spectral
purity
of
swept modes,
and to
improve
tracking
performance
(especially
in
harsh environments
having
wide
temperature variations).
1.
Press
[SHIFT]
[PEAK].
AUTO TRACKING
appears
in
the
ENTRY
DISPLAY
for
5
to
10
seconds.
When
the
message
disappears,
the
instrument
has
completed
the
power
peaking
function
and updated
working
calibration
constants.
SHIFT PWR SWEEP
(HP-IB:
SHPS)
This
function
decouples
the
90 dB
step
attenuator
(ATN)
from
the
automatic
leveling
control
(ALC).
To
recouple
the
attenuator and
ALC
loop,
press
[POWER
LEVEL].
SHIFT SLOPE
(HP-IB:
SHSL)
This
function allows front
panel control
of the
90 dB
step
attenuator
(ATN).
1.
Press
[SHIFT]
[SLOPE].
ATN: xdB
appears
in
the
ENTRY
DISPLAY
(x is
the
last
entered
value).
2.
Use
the
[STEP]
keys
or
the
data
entry
keyboard with
any
termination key
to
change
the
ATN
value
within the
range
0
dB
to
—90
dB in
10
dB
steps.
Keyboard
entries
are
rounded
to
the
nearest
10
dB.
The
clicking
sound heard
after each
attenuator
change
is
the
attenuator
pad
mechanically switching
into
the
RP
output
path.
A-30 Assembly-Level
Service
Front
Panel
Diagnostics
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English