HP 8340A Operating Manual page 342

D. If the power will level at some frequencies and not others while the instrument is
sweeping, the SYTM may not be tracking correctly.
feature by pressing
E. If the power will level at some CW frequencies and not at others, press
optimize the SYTM tracking at the frequency of interest.
F. If the power is unleveled in Band 0
in the switching circuits on the A25 ALC Detector board, the A26 Linear Modula­
tor board, the Al2 Band 0 detector, or the associated microcircuits.
G. If the power is unleveled in bands 1-3 (2.3 GHz to 26.5 GHz) only, suspect a prob­
lem in the switching circuits on the A25 ALC Detector boa rd, A26 'Linear
Modulator board, the All Band 1-4 Detector, or the associated microcircuits.
Refel' to the ALC Loop Ovel'view in Section III of this
volume.
9. OVERMOD ANNUNCIATOR
Overmod indicates that the RF power is turned completely off and a signal (AM or,
if instrument is so equipped, Pulse Modulation) is attempting to shut it off even
further. Make sure an external AM signal is not exceeding specified voltage limits
(the AM input allows a 0 to +-1 volt signal).
10. SRQ ANNUNCIATOR
To understand the
necessary. The way the SRQ works is described below:
SRQ is only used when the instrument is connected to an external controller (via
IB). The controller picks one or more conditions under which the HP 8340A will
send out a service request (SRQ).
send an SRQ when one of these conditions occurs.
When one of the programmed conditions occurs, the HP 8340A sends out an SRQ
signal and activates the
When the controller responds to the SRQ (by doing a serial poll command) the
8340A turns the
SRQ
second, so the time the
SRQ Annunciato1· Stays On
If the annunciator goes on and stays on it usually indicates that one of the
SRQ
following conditions exists:
A. IF THE HP 8340A IS CONNECTED TO AN EXTERNAL CONTROLLER:
·computer controller is not able to service the SRQ interrupt. This problem is
usually caused by the controller being stuck in a loop, etc, and not by a fault in
the instrument.
HP 8340A - Appendix A
[SHIFT] [PEAK).
(JO
NOTE
annunciator, a brief description of SRQ (Service Request) is
SRQ
The controller then programs the instrument to
annunciator.
SRQ
annunciator off. This entire process takes but a fraction of a
annunciator stays on is normally very brief.
SRQ
- 8 -
Scans by HB9HCA and HB9FSX
Try the AUTO TRACKING
MHz to 2.3 GHz) only, suspect a problem
to
[PEAK]
HP­
HP
the