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HEWLETT-PACKARD


JOURNAL
TECHNICAL INFORMATION FROM THE -hp- LABORATORIES Vol. 6 No. 6

ISHED BY THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA FEBRUARY, 1955




A New 10 MC to 12 KMC
Coaxial Crystal Detector Mount
ANEW general-purpose coaxial crystal de from the mount is provided at a negative polarity.
tector mount has been developed to operate Either of the physically- identical 1N26A or
over the entire range from 10 megacycles to 12.5 1N76 silicon crystals can be used in the mount,
kilomegacycles. Since this range is essentially but it is supplied with a type 1N76 and this type
the complete range practical is available for replacement purposes. To assist
SEE ALSO: for coaxial systems, this one in obtaining the wide frequency range that the
"New Decade
Counters," p. 2 mount can be used for all or mount has, the crystals are modified by removing
"New Matching
Transformers," p. 4 dinary coaxial-system detec part of the outer shell. Crystals on which this
tor applications. A feature of modification has been made are available for
the mount is that it has been designed to have replacement purposes, although the modifica
reduced sensitivity to variations in crystal char tion can also be made by the user.
acteristics. Crystal detector mounts of this type are gen
The new mount has a rated sensitivity of ap erally used in one of two applications: as de
proximately 0.1 volt per milliwatt and a maxi modulators for pulse-modulated power where
mum input power rating of 1 milliwatt. Its it is desired to view the pulse shape on an oscil
frequency characteristic is such that its output is loscope, or as simple detectors of r-f power. In
constant within approximately 4 db over the simple detector applications, the power can be
rated frequency range for a constant applied either modulated or c-w. With modulated power
power. Its VSWR does not exceed 3:1. Output the mount can be combined with a suitable a-c
indicator such as a standing-wave indicator or
high-gain voltmeter. With c-w power the mount
can be used with a d-c microammeter.
As is customary with detector mounts, no
video load resistor is included in the mount,
since the value of the load resistance usually
must be chosen to suit the application. When
using detector mounts for viewing pulses on an
oscilloscope, the load resistance should be se
lected commensurate with the required pulse
rise time and oscilloscope sensitivity. The mount
has an output capacity of approximately 30 mi-
cromicrofarads. Typically, therefore, rise times
in the order of 0.1 microsecond can be obtained
with load resistances of a few hundred ohms in
Fig. 1. New -hp- Model 420 A Crystal Detector Mount operates
orer 10 me to 12 kmc range. the usual set-up. If the applied r-f level is ap-

P R I N T E D I N U . S . A . C O P Y R I G H T 1 9 5 5 H E W L E T T - P A C K A R D C O .