See the Non-Volatile Memory discussion in Section 2.17 for more information on
the PPM memory capabilities.
13
Spin Knob The spin knob changes the value of selected parameters. The usability of the knob is
indicated in the display by the appearance of a delta symbol (∆) next to the name of
the parameter of interest. For instance, when in the Peak mode, a Cursor Delay entry
will cause the delta symbol to appear next to DLY in the power reading display.
This means that the spin knob can be used to change the Cursor Delay setting.
14
Detector Select
A or B
(8502A only)
These keys select which channel should display data on the Model 8502A display.
They also tell the instrument which channel a trigger level entry is intended for. In
the CW and Peak Modes it is possible to display measurements for either channel A
or B, or both at the same time. In the Graph Mode, only one channel at a time can
be viewed.
15
Peak, CW,
Graph
These mode keys select whether the PPM will be used for CW or Peak power
measurements. GRAPH is used when making Peak power measurements to allow the
graphic display of the detected pulse and easy determination of pulse timing factors.
In addition to the readout display indications, the selected mode is identified by
which LED in the center of the PEAK, GRAPH, and CW keys is lit. If the Model
8502A is being used for dual channel operation and all of the mode LED’s are out,
then it is in the Ratio Mode (see the Power Ratio Measurement Procedures in
Section 2.10.5).
When the 8502A Ratio Mode is in use, the A and B keys call up a menu so that the
type of signal (CW or Peak) can be specified for the selected channel. This is useful
for determining the ratio between a CW and a Peak signal. For example, a radar
TWT might have a pulsed output but its input could be CW. To measure its gain, the
Peak output would have to be divided by the CW input. The 8502A does this
instantly and automatically.
16
Detector Input These receptacles provide the input from the A and B channel detectors in the
Model 8502A. The Model 8501A has a single input.
17
Calibrator The CALIBRATOR connection performs an amplitude response calibration of the
detector from -30 dBm to +20 dBm, as well as standardizing the absolute power
level readings (see the Self-Calibration Procedure in Section 2.7).
Operation
Manual No. 20790, Rev C, November 1998
2-9
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