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Model 5065A
Circuit Diagrams, Theory, and Maintenance
S E C T I O N I
GENERAL I N F O R M A T I O N
1-1. INTRODUCTION
1-8. TERMINOLOGY
1-2. Description
1-3.
The Hewlett-Packard Model 5065A Rubidium
Vapor Frequency Standard is a compact, self-contained
secondary frequency standard which uses an optically-
pumped Rubidium vapor cell as the reference element.
A 5 MHz oscillator is stabilized against a natural
atomic
resonance,
the
hyperfine
transition
of
Rubidium
87. This technique produces a long-term
stability of better than 1 x 1 0 - " per month with
excellent short-term stability which is conservatively
rated at less than 5 x 10-
12
rms averaged over a one-
second period. Output frequencies are 5 MHz, 1 MHz,
and 100 kHz.
1-4. Frequency setting for any offset of the UTC time
reference is accomplished by changing the microwave
excitation frequency and the magnetic field applied
to an Rb
67
vapor cell.
Thumbwheel switch control
(of a digital frequency synthesizer) provides approxi
mate step adjustment of the microwave excitation fre
quency with a range of 1000 parts in 10
10
. In addition,
the front-panel MAGNETIC FIELD control
provides
for exact adjustment of the Rb
87
hyperfine transition
with a resolution of 2 parts in 10
12
.
1-5. Options
a. A digital clock, Option 001, provides a clock dis
play and a one pulse per second (1 PPS) electrical output.
The clock pulse may be retarded up to 1-second in incre
ments as small as 1-microsecond and as large as 0.1-
second. In addition, a separate control provides contin
uous adjustment of clock-pulse delay from 0- to 1-
microsecond.
b. Standby battery, Option 002, provides a 10-
minute minimum power source (at 25° C) in the event
of external ac power failure.
A front-panel
lamp
flashes when ac power is interrupted and lights con
tinuously during fast charge.
Charge rate is con
trolled by a 3-position
front-panel
switch;
FAST,
CHARGE-FLOAT, RESET.
1-6. Circuit Checks and Outputs
1-7.
The CIRCUIT CHECK switch and meter provide
continuous monitoring of outputs and other signals.
The CONTINUOUS OPERATION lamp gives an indi
cation of correct operation. The 5 MHz, 1 MHz, and
100 kHz output levels are at least t volt rms when
properly terminated with 50 ohms.
1-9.
The definitions of the following terms apply to
these terms as used throughout this manual.
a. ATOMIC TIME.
Time scale based on the
hyperfine resonance of Cesium 133.
b.
UNIVERSAL TIME (UT2).
Time scale based
on the earth's rotation about its axis with correction
for angular position and seasonal variations; proceeds
at a rate slightly slower than Atomic time.
c.
UNIVERSAL TIME (COORDINATED) (UTC). A
piecewise uniform scale which approximates UT2 to
0.1-second by step adjustments in phase as announced
by the Bureau International de I'Heure in Paris.
d.
HYPERFINE RESONANCE OF Rb
87
.
Hyper
fine resonant frequency arising from the difference
in energy between the upper and lower ground states
of Rb
87
.
e.
RVFR (Rubidium Vapor Frequency Reference).
The assembly which houses the Rb
87
lamp, filter cell,
the Rb
87
absorption cell, and the harmonic generator/
mixer diode.
1-10. SPECIFICATIONS
1-11.
Table 1-3 lists the technical specifications for
the Model 5065A.
1-12.
Table 1-1 lists equipment supplied and Table
1-2 lists accessories available for the Model 5065A.
1-13. INSTRUMENT IDENTIFICATION
1-14.
Hewlett-Packard uses a two-section nine-digit
serial number (0000A00000) mounted on the rear-
panel to identify this instrument.
The first four digits
are the serial prefix and the last five digits refer to the
specific instrument. If the serial prefix on your instru
ment differs from that listed on the title page of this
manual, differences exist between the manual and
your instrument. Lower serial prefixes are documented
in Section VII and higher serial prefixes are covered
by a manual change sheet included with the manual.
If this sheet is missing contact the nearest Hewlett-
Packard Sales and Service office (lists are provided
at the rear of this manual).
1-1
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