User`s guide

19
In addition to the above
manuals, the command preview
and key-logging capability of
IBASIC allow you to see on the
screen or insert in the program
the remote command
equivalents of front-panel key
presses. This greatly reduces
the need for the instrument
programming manual. These
features are accessed under the
IBASIC Miscel menu,
followed by key log. Select
PREVIEW for screen display, or
ON for inserting lines into the
program. Press OFF to
terminate the key-logging mode.
Changing Defaults
The program can be modified so
that it comes up with the all of
the variables preset to your
measurement needs, with the
exception of the source HP-IB
addresses and types. To change
the defaults, make sure the
program is not running and the
USER keys are selected, and
type:
edit “default_values”
After you have changed the
appropriate values, be sure to
re-save the program onto a
memory card or floppy disk. If
you get an error indicating that
the card or disk does not have
enough room to hold the
program, it may be necessary to
delete the old file first, and then
save the current program with
the same name as before.
Modifying the
Program
The group delay personality for
the HP 71500A may be modified
as necessary to tailor it to your
particular measurement needs.
Manuals
The following manuals will be
helpful for modifying the code:
HP 71500A IBASIC User’s Guide:
70820-90055
HP 71500A Programming
Manual:
70820-90053
HP IBASIC User’s Handbook:
E2083-90005
HP BASIC Condensed
Reference:
98616-90005
All of the commands in the
condensed reference which are
compatible with IBASIC are
indicated by IN. An asterisk *
following the IN indicates that
some restrictions or extensions
may apply.
When using the FFT zoom
mode, the highest peak function
of the markers can be used to
track an LO that is drifting
slightly during the measurement.
Larger zoom factors result in
less tolerance to LO drift during
the measurement, since the
frequency span becomes
smaller. If the sidebands drift
out of the displayed frequency
span, then obviously the
measurement will be invalid.
The direct demodulation mode
has the most tolerance to LO
drift and residual-FM. Even if
the LO drift is small enough to
allow the measurement to be
done, it can cause degradation
of the group delay accuracy.
Adding Sources
To add support for a different
synthesizer, the following
routines in the program must
be modified:
Easy_read
Reset_source
Set_freq
Set_mod_freq
Set_power
Set_output
Set_modulator
Set_mod_pct
Set_mod_dev
Check_assign
Source_menu
Where needed, add the
appropriate output commands
that are consistent with the
programming syntax for the
new synthesizer.