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HEWLETT-PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S
Vol. 10 No. 3-4
PUBLISHED BY THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA NOV. -DEC., 1958
5 x 10'VWeek Time Base Accuracy
in the 10 MC Frequency Counter
REFINEMENT of techniques in several for example, that a measurement of a 100-
fields is currently generating a need for megacycle frequency (using the counter with
making routine frequency measurements to in its heterodyne converter) will be accurate with
creased degrees of accuracy. A good example in ± 5 cycles in the week following calibration
of this need lies in the single-sideband field or ±10 cycles in the second week, ± short-term
where it has become desirable to be able to stability in each case.
make fast, convenient meas Actually, the performance of the oscillators
urements of VHP frequencies has been well above ratings, and the ratings are
to within a matter of cycles in considered to be subject to later improvement.
checking transmitter carriers, receiver oscilla Short-term stability, for example, is rated as
tors, filter response, etc. within ±3 parts in 108, but typical short-term
For such work the -hp- 10-megacycle fre performance is considerably better, as shown in
quency counter is now available with a new Fig. 2. Note that one major vertical division in
time base crystal oscillator of very high per Fig. 2 is equal to 1 part in 108 so that the sta
formance. The new time base is rated as having bility can typically be described in parts in 109.
a long-term stability of within ±5 parts in 108 It is of interest to recall that this performance,
per week. This tolerance is directly transfer while within about one order of magnitude of
able to frequency measurements and means, that of most high-quality commercial crystal
L. 1 5 MIN.