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Chapter 6 Specifications

Footnotes

Operating and Programming Manual

115

Footnotes:

Accuracy:

The degree to which the 5071A output

frequency differs from that of the accepted
definition.  The currently-accepted definition is that
of the 13th General Conference of Weights and
Measures and is based on Cesium (The hyperfine
resonance of the Cesium 133 atom in zero magnetic
field is 9.192631770 GHz.).  In practice, this
involves comparison with some generally-accepted
physical embodiment of this definition such as one
of the time standards in the international time scale
(TIA) monitored by the BIH (Bureau International
L'Heure) in Paris, France.  The specified accuracy
of the 5071A is intrinsic and is maintained without
calibration.

Flicker Floor:

The level at which the Allan

variance time domain stability measurement
remains constant with increased averaging time.
The Allan Variance statistical method for
measuring time domain stability responds in
several ways to various noise processes in a cesium
standard.  Many of these noise processes produce
contributions which average out or decrease as the
averaging time increases.  Flicker noise, on the
other hand, gives rise to an Allan variance
independent of averaging time.  Thus, the Allan
variance of a typical frequency standard will
decrease with increasing time, until a relatively
constant value is reached.  This value is known as
the

flicker floor.

Flicker Floor Value, Typical:

Typical flicker floor

performance measure is based on long-term
measurements made by NIST.

Frequency Domain Stability:

(also called single-

sideband phase noise or additive noise). Describes
the spectral noise in the specified output signal
caused by phase modulation from internal noise
sources.  The measurement is normalized by
expressing the ratio of noise power (in a 1-Hz
bandwidth) to the signal power, then measured as a
function of offset from that signal.  For more
information see NIST Technical Note 1337,
Characterization of Clocks and Oscillators
available from the Superintendent of documents,
U.S. Government Printing Office, Washington DC
20402-9325.

Frequency Settability:

The degree to which the

frequency of the 5071A may be adjusted to
correspond with a reference without loss of
stability.

Isolation:

The degree to which one output of the

5071A is affected by changes in loading on another
output of the same standard.  In practice, this
represents a change in amplitude, frequency, or
phase as seen at one terminal due to the effect of
placing a short, open, or reactance on another
terminal.  In the 5071A, both Port 1 and Port 2 high
isolation output frequencies are derived from the
same source; there is no measurable change in
frequency.  The change in amplitude or phase is
measured as the level of the sideband at one port,
which results from applying and removing the load
at a low frequency rate at the other port.  The
measurement is the level of the resulting sideband
compared to the nominal output level, expressed in
decibels.

Reproducibility:

The degree to which the 5071A

will reproduce the same frequency from one
occasion to another after an interruption in
operation. This does not include any calibration
procedure but may require degaussing.

Supplemental Characteristics:

Specifications

refer to the instrument‘s warranted performance.
Supplemental characteristics are typical or nominal
values intended to provide information useful in
applying the instrument.