[time-nuts] time-nuts, frequency counters

[Scott Mace]

I picked up one of the Lucent RFG-RB units on ebay and sure enough it was
off, but not by much.  It was manufactured mid 2001.  I adjusted the
C-field pot while comparing it to my best z3801a.  I'm waiting on a
new GPIB interface to see just how well I did.  The LPRO-101 in the
RFG-RB makes about 15W of heat.  I gently clamped it to the back heatsink
of the RFG unit and left it on for an hour or two before adjusting with
my counter in TI mode. I thought about drilling a small hole in the top
of the RFG chassis so I could access the C-field pot, but decided I just
liked taking the thing apart...

	Scott

David Forbes wrote:
> CHazlitt wrote:
>> So, here is my question, do Rubidium standards drift that much over a period 
>> of years to where they have to be brought back on frequency? If so, what is 
>> tuned on the Rubidium to do so, C-field? 
> 
> Yes, they do drift over time. There is a spec provided on the data 
> sheet; you can expect the unit to drift at perhaps half of that 
> specified maximum rate. You can adjust the magnetic field to bring it 
> back to center frequency, but sometimes they drift so much (over >10 
> years) that you have to replace a factory-selected resistor to get the 
> trimmer into range.
> 
> The only type of commercially available frequency standard that doesn't 
> drift is a cesium beam clock; their frequency of operation doesn't 
> depend on magnetic fields or buffer gas pressure or anything like that. 
> That's why they're used for GPS etc.
> 
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