HP 8756A How To Use

8 . Press (MANUM LOCKJ. The "LO CKED "
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 w eeper . The sweeper
is n ot 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?
Y es .
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 it 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 m ode, the HP 53448
triggers the sweep, but the s weep er
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 w ill
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 m onic/offset locking . We now carr)
our example fUrther to include counted
markers.

HP 8756A Specifications

General

Brand	HP
Model	8756A
Category	Measuring Instruments
Language	English