User Manual
20
UM-20 Low-cost Oven-controlled Crystal Oscillator (OCXO) Assembly
Usage
DC Voltages
TP1
(12V LDO output) typically measures 11.87Vdc for a +12Vdc
input to the module. Note that this means that the LDO is not
regulating its output.
TP2
(stable 5V for trimpot) will measure close to 4.9999Vdc.
TP3
(OCXO’s VCO) varies for 10.00000000MHz. The trim
voltage seems to be around 4-6mV/0.1Hz.
Note
It was observed that the trim voltage for 10MHz when
installed typically differs from the trim voltage when the PCB
assembly is on a bench and not installed in an XL Microwave
Model 3xxx.
-WARMING
rises to 4.87V once the OCXO is out of its warm-up
phase.
The total current (@12V) when warming is 250-300mA,
post-warming is 85mA. The 180mA trip threshold of
U2
is
therefore confirmed.
Loading vs. Frequency
The output of the OCXO changes slightly with loading,
particularly capacitive loading. The output does not have an active
buffer. The frequency difference between the OCXO assembly
running on a bench, into a high-impedance oscilloscope, and the
10MHz output frequency from the Model 3xxx, is in the region of
0.5Hz, or 50ppb.
Frequency Stability
Once installed in the Model 3xxx, the frequency of the OCXO
PCB assembly is measured at the Model 3xxx’s output BNC on its
back panel. These tests were performed without any thermally
encapsulating epoxy on the PCB assembly.
Summary of Contents for UM-20
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