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8
.
Press
(MANUM
LOCKJ.
The
"LOCKED
"
light wi l1 appear on the right, and
the
counter
should
display
the
start
frequency.
QUEST
IONS
/
ANSWERS
Q,
A,
Q:
A,
Q,
II,
Q,
11m doing
narrowband
sweeps with the
system interface bus connected.
What
will
happen
to
the
frequency
annotation
information
of
the
HP
8756A?
The
HP 8756A obtains
the
O-lOV
sweep
ramp from the
HP
5344S
but
gets
its
frequency
information
from
the
HP
83509
,
which
is
in
cw
mode.
It will
display the sweeper's CW frequency,
not
the HP 53445 sweep frequencies.
IMPORTANT NOTE,
Frequency ad
j
ustments
shoulrl always be
made
on
the HP
5344A until lock is lo'St
.
Then
the sweeper
must
be
readjusted
to
within
25
MHz
of
the
desired
lock
frequency.
I'm
using a narrowband sweep in CF
/
6.F
mode.
When
I reduced
6.F
to zero, the
sweep stopped on
the
HP 8756A.
Why?
The
HP
53445 treats
this
case
as if
it
were
in
CW
mode.
In
cw
mode the
HP
5344S
does not generate
its own sweep
signal
,
but will pass
the sweep signals
through
from
the
s weeper
.
The sweeper
is
not
generati
ng
any sweep in
regular
CW
.
You need swept cw.
Press
(SHIFTJ
[ewJ
to
enter the
HP
83508 swept CW
mode, and the sweep continues.
will this
also happen in
STRT/S
TOP with
the start frequency the same as the stop
frequency?
Yes
.
Can
I use
the
HP
5344S
markers
to make it
more
convenient
to analyze
the trace?
No,
not
when
the 8756 System
Interface
is
operating
.
These markers
can be
used
without
the
System Interface, as
descr
ibed
in
the
section
"Ques-
tions
/
Answers
Regarding Markers"
at
the
end of
this paper.
LOCK AND ROLL SWEEPS
The
HP 53445 can be used
to improve
the
accuracy
of
wideband sweeps in
lock and
roll
(LK/R)
mode.
The HP
5344S inhibits
the HP 83508
sweep
until i t
phase
locks to
the
start
frequency,
and then releases
the
HP 8350B to sweep
on
its
own
.
The start
frequency
error
is
essentially
removed,
and
frequency
error
is
thereby
reduced
to
the
linearity of
the
sweeper.
In
this
mode,
the sweeper
generates
the display
signals, and the
HP 5344S passes
Z
AXIS IN
to Z AXIS
OUT
and
SWEEP IN to SWEEP
OUT. It
also uses
these
sig
nals
to hold the sweep
until
it
locks
the
HP
83508
start
frequency,
and
then triggers
the sweeper
externally
using
the
HP
5344S
sweep
trigger
signal.
In LK
/R
mode,
HP
83508
6
markers can
be counted
by the HP
5343A
counter using the special
sweeper interface
of
the
HP
5343A.
This
function
is
detailed later.
The example shows a lock and roll
swee
from
I
GHz to
20
GHz wi th a sweep
time
of
20Lr
ms
.
1. Using the
(MODEJ
key
on
the HP
5344A,
scroll to the LK/R mode.
2
.
Enter
t~e
desi ren lock frequency
on
the HP 5344A which should be the same
as the sweeper's start frequency
.
This
is the
FI
function in this mode
.
Press (FlJ
[lJ
[GHzJ
.
3
.
Set the
start
frequency
o
n
the
HP
83508.
Press
(STARTJ
(lJ
[GHzJ.
This puts
the sweeper
in
start/stop
mode.
4.
Then
set the stop frequency on
the HP
83508
.
Press (STOPJ (2J (OJ
[GH
zJ.
5.
Set
the sweep time on the
HP 83508
.
Remember, in
LK/R
mode, the HP
53448
triggers the sweep,
but
the s weeper
generates
it
.
Therefore,
the
sweeper
controls
the
sweep
time.
Press
[TIMEJ
[2J
[OJ
(OJ
(msJ.
6.
Disable the
RF
plug-in
'
s
CW
filter.
On
HP
83500
series
plug
-in
s
press
[ew
FILTERJ.
For
86200
ser
ie
plug-ins,
set
the
rear
pant
FM
/
NORM
/P
L
switch
to
PL
(phase
lock).
"Err
05"
will
be displayed
on the HP 5344A if
you
try to lock
the
source while
the
CW
filter
is on.
7
.
Set
the
HP
83508 SWEEP
external.
Press
[EXT]
SWEEP
TRIGGER
heading
.
TRIGGER to
under
the
8.
Press
(MANUAL
LOCKJ.
The
"
LOCKED"
annunciator should
light
and the
counter should display
the
start
frequency.
The
HP
8756A
will
display the measurement
data on
the
CRT.
COUNTING SWEEPER MARKERS
IN
LOCK AND ROLL
In
LK
/R
mode
with
the
HP 5344S
o
pt. 43
(HP
5343Acounter) the sweeper markers can be
counted very
accurately
using the sweeper
interface
function
of
the HP
5343A
.
Note
the sweeper interface cables A and B shown in
figure
4.
These outputs are
available
only
from
the
HP
5343A counter and enable the
marker
count
function.
They
are
not
necessary
for
normal
operation.
This
function
can be used
whether
or not the
8756
System
Interface
is
operating
,
ar
can
operate
in
either
normal
subhar monic/offset
locking
.
We now carr)
our
example
fUrther
to
include
counted
markers.
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