User Manual
UM-20 Low-cost Oven-controlled Crystal Oscillator (OCXO) Assembly
21
Over the course of several days, when monitored by a Model 3020
using a GPS-disciplined 10MHz oscillator as its external frequency
input, and with the OCXO131-40 tuned to 10,000,000.00Hz, a
maximum change of -.01Hz / + 0.00Hz was observed. This is 1E-9
territory, which is within the IsoTemp OCXO131 specifications of
±0.5ppb over the course of one day.
An SRS SR620 time interval counter was setup with a 0.01s gate
period and a sample size of 1,000 to measure Allen variance; the
result was relatively stable around 27 to 33 mHz, or 2-3ppb over a
τ
of 10s. This number is in keeping with plots of typical OCXO
frequency stability.
Warmup / Initial Behavior
It was observed that compared to the OCXO36-based (double-
oven?) oscillator, the smaller OCXO131-based oscillator warms up
very quickly, is closer to 10.000MHz at initial turn-on, and reaches
the post-warmup stage sooner.
Oscillator Outputs
The output of the OCXO36-44 through the Model 3xxx’s 10Mhz
output terminated into 50
Ω
is shown Figure 8.
Figure 8: OCXO36-44 waveform (blue) compared to
Z3805A GPS-disciplined waveform (yellow)
The output of the OCXO131-40 through the Model 3xxx’s 10Mhz
output terminated into 50
Ω
is shown Figure 9.
Summary of Contents for UM-20
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