HP 8340b User Manual

When
a
bandcrossing
or
end
of
sweep
is
reached,
LBX
(low
bandcross)
and
HSP (high
sweep)
are
pulled
low
by
the
A57
marker/bandcross assembly.
This
causes
VSWP to
pause
(stop
ramping).
The
instrument
processor
pulls
LRSP
(low
reset
sweep)
low,
resetting
VSWP
to
zero
volts.
To
eliminate
unwanted
magnetic hysteresis,
the
instrument
processor
initiates
a
retrace
kick
via
the
YO
retrace
kick
pulse
generator
in
the
A54
YO
pretune/delay
compensation
assembly.
This
pulse
is
sent
to
the
ASS
YO
driver
where
it is
converted
to
a
60
ma
current
drain
on
the
YO
drive
current.
This
temporarily offsets
the
YO
frequency
by
approximately
—2.5
GHz,
eliminating
the
magnetic hys¬
teresis
in
the
YO.
Finally,
the
instrument
processor
sets
PRETUNE
to
a
value
proportional to
the
next
lock
frequency.
When
the
loop
is
locked,
the
sweep
sequence
is
repeated.
In
sweeps
where
the
YO
is
to
sweep
5
MHz
or
less,
the
20-30
loop
is
swept
and
the
YO
loop
remains
phase-locked.
Since
the
YO
loop
is
phase-locked
to the 20-30
loop
output,
the
YO
frequency
will
follow that
of
the
20-30
loop.
The 20-30
loop
is
swept
by
a
voltage
ramp,
20-30
SWP,
generated
by
the
ASS
sweep
generator
assembly.
For
YO
sweeps
<500
kHz,
the
sweep
width
range
attenuator
on
the
ASS
sweep
generator
assembly
is
open-circuited
so
that
VSWP
remains
at
zero
volts.
START/STOP
Sweep
Operation.
Starting
and
stopping
the
sweep
ramp
is
controlled primarily
by
high
sweep
(HSP),
which
is
generated on
A57
marker/bandcross assembly
(located
in
the
controller
section).
When
HSP
is high,
the
ASS
sweep
generator
is
free to
sweep.
When
HSP
is
low,
the
ASS
sweep
generator
stops,
but
does
not
reset
sweep voltage,
VSWP.
The
AS7
marker/bandcross
assembly
pulls
HSP
low,
stopping
the
sweep whenever
any
one
of
the
following
three events takes
place.
•
LBX
(low
bandcross)
goes
low.
The
AS7
marker/bandcross
assembly
pulls
LBX
and
HSP
low
at
bandcrossings
and
at
the
end
of
the
sweep.
The
ASS
sweep
generator
pulls
LBX
low
if
there is an
instrument
malfunction
that
allows
VSWP
to
go
beyond
its
normal
limits.
•
LSSP
(low
stop
sweep) on
the
rear
panel
is
pulled
low.
Note:
this
line
is
meant
for
special,
dedicated
applications
and
is
not designed
to be
a
general
purpose
stop
sweep
input.
•
The
instrument
microprocessor
issues
a
STOP
SWEEP.
The
AS7
marker/bandcross assembly
drives
HSP
high,
starting a
sweep whenever
any
one
of
the
following
three events
takes
place.
•
A
line
trigger
input
is
received
after
line
trigger mode
has
been
selected.
•
An
external
trigger
input
is
received after
external trigger
mode
has been
selected.
•
The instrument
processor
issues
GO
SWEEP
IMMEDIATE.
•
LSSP
on
the
rear
panel
goes
high
after
the
instrument
processor
has
completed
its
tasks and
is
waiting for
the
input.
The
AS7
marker/bandcross assembly controls
the timing
of
the
various
sweep events
(marker on/off,
bandcross,
and
end
of
sweep)
by
monitoring
MKR
RMP.
This
is
a
zero
to
ten
volt
ramp generated
by
the
ASS
sweep generator assembly.
A
buffered
version
of
this,
SWEEP
OUTPUT,
is
available
on
the
front and
rear panels.
MKR
RMP
pauses
for
bandcrossings.
It
starts at
zero
volts
at
the beginning
of
each
sweep.
It
reaches
five
volts at
the
center
frequency
of
the
sweep
and
goes
to ten
volts
at
the
end
of
the
sweep.
D-8 Sweep
Generator
-
YO
Loop
Theory
of
Operation
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English