Home Digital Drive

Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it.

RE: Rubidium clock not locking


I also have a feeling that the frequency reference itself is not locking,...

Yes, that was my first point. You have to determine if the Rb clock is locking otherwise the 10MHz output signal is likely to wander (deliberately) as it tries to lock.

The OCXO oven should draw significantly more current at initial power ON while it's cool and then the current tapers off to a lower steady state level. If this is not happening, there's a chance that the oven heater is out. Let the Rb clock rest for a period of time so it is completely cool, then power it up and measure the current draw over time.

You really need a frequency counter and oscilloscope to trouble shoot. We had Tracor frequency difference meters to compare the output of a Rb clock against known reference.

You could poke around with a DMM to see if you have heater voltage. There are many other things to check including the Rb lamp. If you open the unit up, you should be able to see the light from Rb lamp but it might be buried within the physics module. If the lamp doesn't light a couple things could be wrong. There's no heat to create vapor from the Rubidium metal within the lamp. RF is used to excite an inert gas within the bulb creating a plasma to help heat the Rubidium. The RF might be out.

Most 'repair shops' have never seen an Rb oscillator so hopefully you'll find a very sharp tech.




Edits: 01/07/15

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