[time-nuts] Name That Rb Frequency Standard

Richard H McCorkle mccorkle at ptialaska.net
Tue Jun 12 17:27:39 EDT 2007


I believe he is referring to the Efratom FRS-C Rb oscillator which
was very popular in telecom applications. I looked at the specs for
one on eBay (140128295361) and in my FRS-C manual and came up with:

FRS-C Electrical Specifications:
Long-term Drift: < or = to 5x10-11/mo*, < or = 5x10-10/first year,
< or = to 2x10-10/year thereafter.
Trim Range: +/- 2x10-9 max.

The electrical tuning description in my manual lists the adjustment
range as +/- 1e-9 to +/- 1.5e-9.

He states "the manufacturer provides a C-field adjustment range
equivalent to +1.5E-9" which is similar to the tuning description
in my manual, and he states "The aging rate of the standard is
specified as 2E-10/year" which is the same as the long-term drift
spec listed on the eBay unit.

So my entry in the "Name That Rb Frequency Standard" contest is the
Efratom FRS-C. When will the winners be notified and what prizes
are offered?

BTW, the 7.5 year life due to limited C-field range is well beyond
the typical Rb lamp life I have experienced with these units, which
has been more like 3-5 years of continuous operation with a new
lamp and a heavy duty heat sink on the unit. A few units I have
worked with did somewhat better than this, but I personally haven't
come across an FRS-C yet where the C-field range couldn't put the
unit on frequency if everything else was working properly.

Having Fun!

> Hi:
> Came across US patent 4,899,117 "High Accuracy Frequency Standard and Clock
> Sytem" by John Vig, Feb. 6, 1990.
> http://www.google.com/patents?id=068BAAAAEBAJ&dq=4899117
> In the background section he says:
> "For example, in one of the most popular Rubidium frequency standards on the
> market, the manufacturer provides a C-field adjustment range equivalent to
> +1.5E-9.  The aging rate of the standard is specified as 2E-10/year.
> Consequently, at the specified aging rate, the limited C-field adjustment range
> limits the useful life of this Rubidium frequency standard to 1.5E-9/2E-10 or
> 7.5 years."
> Which standard is he reffering to?
> --
> Have Fun,
> Brooke Clarke
> http://www.PRC68.com
> http://www.precisionclock.com
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