HP HP 8753E, User Manual, Page: 289 / 699

Active Channel Keys
The analyzer has four channels for making measurements. Channels 1 and 2 are the primary
channels and channels 3 and 4 are the channels. The primary channels can have
different stimulus values (see “Uncoupling Stimulus Values Between Primary Channels,” below)
but the auxiliary channels always have the same stimulus values as their primary channels.
That is, if channel 1 is set for a center frequency of 200 MHz and a span of 50 MHz, channel 3
will have the same stimulus values. This permanent stimulus coupling between primary and
auxiliary channels is:
Channel 1 = channel 3 (by stimulus)
Channel 2 = channel 4 (by stimulus)
This stimulus coupling between a primary channel and its auxiliary is reciprocal; if you change
a stimulus variable in an auxiliary channel, it immediately applies to its primary channel as
well.
Figure 6-3. Active Channel Keys
The and shown in Figure 6-3 allow you to make a channel “active.
Once active, a channel can be configured independently of the other channels (except the
stimulus values of an auxiliary channel, see above). The front panel and are
used to configure a channel while it is active. All of the channel-specific functions that you
select apply to the active channel.
Primary channels 1 and 2 can be made active anytime by pressing
or
respectively. However, before you can activate channel 3 or 4 through these keys,
you must do two things:
1. Perform or a full two-port calibration.
2. Enable the auxiliary channel through the menu.
Note The and keys retain a history of the last active channel . F FF or
example, if channel 2 has been enabled after channel 3, you can go back to
channel 3 without pressing twice.
Auxiliary Channels and Two-Port Calibration
A full two-port calibration must be active before an auxiliary channel can be enabled. The
calibration may be from a previously saved instrument state or performed before
enabling an auxiliary channel. If recalled, you may need to modify some of the parameters
from the instrument state in order to apply it to your particular device. The recalled
calibration must cover the range of the device to be tested.
If a calibration is performed while one or both auxiliary channels are enabled, the auxiliaryy
channels will be disabled, then enabled when the calibration is complete.
6-6 Application and Operation Concepts