If the New Data light on the front panel of the PPM does not flash, then the instrument is not
triggering. If the trigger level is at -20 dBm and no trigger occurs, there might not be enough
power at the detector input to be able to measure. If this is the case, recheck the calculations that
were made to decide what attenuation levels were required to prevent detector burnout. If
necessary, reduce the attenuation at the detector input by 10 dB to increase the power so that the
PPM will trigger.
☛
NOTE: If a TTL Trigger signal is available from the source being measured, then using the
External Trigger Mode is advisable. If an oscilloscope is available, the PPM’s rear panel
MONITOR OUTPUT(s) can be used to determine the proper timing settings for the
instrument.
11.
Once the PPM is reading power as desired, press [FREQ] and enter the frequency of operation
(or Cal Factor).
12.
To obtain the absolute power output of the RF source being measured, use the PPM’s Offset
feature to offset the displayed values by the combined attenuation values of the coupler and/or
attenuators being used in series with the detectors. Most couplers and attenuators have
attenuation versus frequency response curves supplied that can be used for exact entry of the
required offset. To enter the Offset, press [MENU] (3) [F1] [nn.nn] [dBm].
Where nn.nn is the Offset desired. For channel B offset on the 8502A, use F2 instead of F1. When the
Offset feature is in use, this will be shown on the display by an asterisk (*) next to the FREQ or CF
indication.
2.12.1
High Power Relative Measurements (8502A only)
The procedure for making a gain or loss measurement is the same as for absolute power, but requires
activating the Ratio Display function of the 8502A. The Offset feature compensates for external devices
before entering the Ratio Mode (see Power Ratio Measurement Procedures in Section 2.12 for more
information on ratio’ing).
Operation
Manual No. 20790, Rev C, November 1998
2-39
Summary of Contents for 8501A
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