[time-nuts] Austron 2010B (disciplined OCXO) square wave conversion
csteinmetz at yandex.com
Sat Aug 6 17:19:18 EDT 2016
> Only later did I realize that for some bizarre reason,
> all of the outputs are square wave, not sinusoidal!
> I'd rather use something prebuilt than building my
> own converter
A simple Tee network lowpass filter will do the job -- see the attached
schematic (NOTE: this circuit is designed for 10MHz -- you would need to
scale it for 5MHz and 1MHz). If the input is from 5v CMOS logic (0v
low, 5v high) that will put out at least +/- 30mA and you use a 56 ohm
input resistor, the circuit will deliver a sine wave output of ~1v RMS
(= +13dBm) into a 50 ohm load, which is a common output level for
Mini-Circuits sells a 5MHz LP filter with BNC connectors (BLP-5+), but
it does not include the input resistor or the DC blocking capacitor
shown in the attached schematic -- so you would need to add those
yourself (again, I'm assuming that the Austron output is a DC-coupled,
0-to-5v square wave). Mini-Circuits does not list a 1MHz filter, and
their 1.9MHz filter is not suitable because it wouldn't provide
sufficient attenuation of the 3rd harmonic (3MHz).
You would put the filter between the Austron output and the 50 ohm input
of a distribution amplifier.
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