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Model 423A/8470A
20. Original Packaging. Containers and materials
identical to those used in factory packaging are
available through Hewlett-Packard offices. If the
instrument is being returned to Hewlett-Packard
for servicing, attach a tag indicating the type of
service required, return address, model number,
and serial number. Also, mark the container FRA¬
GILE to assure careful handling. In any corres¬
pondence, refer to the instrument by model num¬
ber and serial number.
21. OPERATION
CAUTION
Static discharge can damage the detector
element. A 100 pF capacitor (1.2 m[4
ft.] of coax cable) charged to 14 volts
stores 0.1 erg, the maximum pulse rating
of the detector element. Connect cables
to test equipment and discharge the cen¬
ter conductor, before connecting to the
detector.
DO NOT NEEDLESSL Y HANDLE DE¬
TECTOR ELEMENT USED IN CR YS-
TAL DETECTOR. Static electricity
which builds up on a person, especial¬
ly on a cold dry day, must never be
allowed to discharge through the crys¬
tal detector. Avoid exposed leads to or
from the crystal detector, since these
are often touched accidentally.
22. Operating Information
23. The crystal detector can be used as a demodu¬
lator to obtain a pulse envelope which can then be
observed on an oscilloscope. It can also be used as
a general purpose detector.
24. When using the crystal detector with an oscil¬
loscope, and the waveshapes to be observed have
rise times of less than 5 ps, the coaxial cable con¬
necting oscilloscope and detector should be as
short as possible and shunted with a resistor. Ideal¬
ly, this resistor should be 50S2 to terminate the
coaxial cable properly. However, with 5012 resis¬
tance, the output video pulse may be too small to
drive some oscilloscopes. Therefore, the cable
should be shunted with the smallest value of resis¬
tance that will obtain suitable deflection on the
oscilloscope; typically the value will lie between
5012 and 2 k!2. The larger the resistance the more
degradation of rise time.
25. The power applied to the detector can be either
modulated or continuous wave (CW). If modulated
at a 1000 Hz rate, an SWR meter can be used as an
indicator. For CW detection, a dc milliammeter or
millivoltmeter can be used as the indicator.
26. Operator's Checks
27. Peak Power Measurement. The arrangement
of equipment for peak power measurement is shown
in Figure 1. The procedure involves calibration of
an oscilloscope which, in turn, is used to calibrate a
CW generator. The output of the calibrated CW
generator is measure with a power meter; the peak
power of a pulse is thereby measured. The proce¬
dure is as follows:
a.
Connect equipment as shown in Figure 1,
step a. Observe pulse on a dc-coupled oscilloscope.
Using a marking pencil, mark on the graticule the
base-to-peak amplitude of the pulse envelope.
b.
Replace the pulse source with a CW gen¬
erator. While observing the oscilloscope trace, ad¬
just amplitude of CW generator output to make de¬
tector's output equal to that of pulse generator,
as indicated by markings on graticule (step a).
c.
Leave CW generator at setting obtained
in step b. Disconnect detector from CW generator.
STEP (a)
Figure 1. Peak Power Measurement
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