HP 8756A How To Use

First, determine the frequency band
you will be using, and determine whether your
plug-in is using a frequency multiplier
technique or a heterodyne technique in the
range of interest. When you place the rear
panel mode switch on the HP 5344A to 5UBHMNC,
subharmonic locking will automatically be
enabled. I t is used when the sweeper plug-
in uses a frequency multiplier technique.
Offset locking will also be automatically
enabled, but must be activated by entering
the offset on the counter. Table 1 shows the
plug-ins for which subharmonic/offset
locking is useful. It also shows which
frequency ranges should use subharmonic
locking and which should use offset locking.
In either subharmonic or offset locking , the
AUX OUTPUT of the s wee per should be connected
to the counter's microwave input.
Subharmonic locking
1. Set the rear panel MODE swi tch of the
HP 5344A to SUBHMNC. This is
indicated by a right hand decimal
point on the front panel display of
the HP 5344A .
2. Connect the RF measurement system,
such as the one shown in figure 5.
The counter input should come from
the plug-in's AUX OUTPUT .
3. Make sure no offset is active in the
counter. The (OFS MHz) key on the
counter should be off.
4. Activate the internal square wave
modulation if you are using it.
Press the [..r MODJ key on the 8350B.
5 . Set up the desi red measurement
according to the instructions in
the appropriate section (CW,
CF / .0.. F, STRT/STOP, LK / R) , and lock
the sweeper using either MANUAL or
AUTO lock.
Any frequency multiplier greater than
four must be entered manually on the HP
5344A. This is unnecessary for HP 8350B
plug -in s in normal operation, since the
n,ultipliers are never greater than four, but
ir : structions are included in the HP 534 45
Operating and Service Manual.
Offset locking
To use offset locking, you must enter the
offset on the counter. For all HP 8350B
plug-ins that can use offset locking, this
frequency is 3.8 GHz with an accuracy of
better than 5 MHz. This offset can be
determined more accurately by counting the
main front panel output and the auxiliary
rear panel output separately. The offset
is then the difference between these two
frequencies. We now show how to use a
frequency offset of 3.8 GHz.
9
1. Set the rear panel mode swi tch of the
HP 5344A t o SUBHMNC. The right hand
decimal on the HP 5344A display
should be on .
2 .
Connect the RF measurement system ,
such as the one shown in figure 5.
The counter input should come from
the plug - in 's AUX OUTPUT .
3. Make sure the HP 53445 is not trying
to lock. The (Ml\NUlIL LOCK) and
[AUTO LOCK) keys should be off.
4. Enter the offset on the counter by
pressing [SET) (OFS MHz) (3) [8J
(0) (0) (CBS) (ENTER). The change
sign key [CBS] is needed because we
are adding a negative offset.
5. Activate the internal square wave
modulation if you are using it.
Press the IJ' MOD J key on the HP
83508 .
6. 5et up the desired measurement
according to the instructions in
the appropriate section (eW,
CF/boF, STRT/ STOP, LK /R) , and lock
the sweeper using either MANUAL or
AUTO lock.
QUESTIONS/ANSWER S
Q: Sometimes I want to use an offset, but
not all the time. Do I need to enter
the same 3.8 GH z offset every time I
change configuration?
A: No, only when the HP 534 45 is powered
on . Just be sure the offset key (OFS
MHz] is active when you want it to be .
You can enable it and disable it by just
pushing the (OFS MHz) key. To check
your offset , press [RECALL] and then
hold down the (OFS MHz) key. The
offset will be displayed on the counter
until you release the (OFS MHz) key.
Q:
A:
Q:
A:
The counter's keys are inactive. I
can't enter anything. What's going
on?
That's because you are trying to lock,
and the counter's keys are disabled.
Unlock the source, and the counter's
keys should function again.
I am counting sweeper markers in lock
and roll mode with subharmonic/offset
locking , and am getting strange
readings. Wha tis wrong?
LK/R sweeps can be very wideband. The
plug - ins typically switch over several
frequency bands during a LK/R sweep.
The counter has no way of knowing which
band the sweeper is in, and whether to
apply an offset or a ha rm onic number.
Therefore, it displays the plug - in ' s
fundamental YIG tuned osc illat or
frequency. You will need to apply the
necessary offset or multiplier to the
frequency displayed by the counter.
Table I is a useful reference for this.

HP 8756A Specifications

General

Brand	HP
Model	8756A
Category	Measuring Instruments
Language	English