[time-nuts] Newbie with new questions: Rubidium

lymex at vip.sina.com lymex at vip.sina.com
Fri Aug 5 12:59:02 EDT 2005

Recently I acquired 10 compact Rubidium modules cheaply

(http://www.dl-car.com/~2038/time/rubidium1.jpg etc.)

made by Efratom between 1991 to 1997. They look identical

internally and perform equally good by my preliminary tests.

By comparing outside appearance with the Rb module FRS-C 

inside SR625 (http://www.dl-car.com/~2038/time/rubidium8.jpg), 

They look very similar.

These modules are taken down from Lucent communication 

equipments which must be running 24hrs a day.

My preliminary test results:

Frequency deviation: 1E-9 max (1hrs warm-up)

Starting supply current: 1.6 - 1.75A

Lock time 145 - 160 second at 28C room temperature.

Current consumption after warm-up: 0.36 - 0.41A

However, I still got many questions.

Q2A. Are these actually FRS-C? or others module?

The module in my SR625 is the FRS-C made in 1992:


Five of my modules labeled 'part # 100334-005', two are

'part # 100334-004', two are 'part # 100334-005'.

Q2B. The first test I did is to measure the frequency because 

the accuracy might be indications for their past drifts. The 

result is very good: max deviation from 10MHz is less than 1ppb 

against my HP58540A (locked to GPS for many days) by using 

HP53131A at a gate time=150 seconds. An example is, #28979 was 

manufacture in 1995, frequency deviation is 0.39ppb, factory 

set at 0.05ppb. Can I say that the long time drift for this 

particular module is <5E-10 in ten years? I know I cannot say 

its 5E-11 per year for sure.

Q2C. Is the life expectancy for rubidium 10 to 20 years?

if so, some of my modules are about to die even if they are still

functioning well? I came across "A Note about Rubidium Oscillators"

at: http://www.amtestpl.com/DATUM/GmbH/Rubidium-Note-e.pdf

saying that life time is virtually unlimited. I'm confused.

Q2D. Anyone have the electronic manual for these Rb?

I'd like to know the pin out specs as to how to use other pins.

Q2E. Power supply. Is a switched mode power supply will be Ok?

What are the side effects if I supply the heater power and 

reg power from the same source?

Q2F. Is it possible to replace the OCXO in the HP58540A with 

the modules to Achieve better holdover result?

Q2G. What is the maximum operating temperature as regard to

ambient and base plate? Do aging Rb modules require cooler 

temperature? I power up some of the modules without any heat 

sink for about 10 hours and 3 of them stop working. Its seem 

that they are over heated at not more than 55C base temperature. 

When cooled down they begin to work again. 

I a good gesture for the rich information here and for all the

people who made the contribution, I'll give away two pieces of

these to any list members who are first and second come to China

from now on. Drop me a e-mail (or follow the thread) before you 

leave, and preferable give me the name and phone # of your 

Chinese friend. After I confirmed, I'll ship the module (at my 

own charge) before hand so that you can get the module once you

've landed in China. The information as to who and when have 

received the module will be posted here.

Have fun.

Lymex Zhang / bg2vo


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