Re: PTB 100 Ball Efratom


stevenhorii
 

I can’t tell you about phase noise, but a key feature of rubidium standards
is their operating life. The life is limited by depletion of the rubidium
in the discharge lamp. Because studies by manufacturers of the performance
of the standards they make, they can provide estimated lifetimes based on
rubidium depletion. Because of the reliability requirements of frequency
and time standards (for example in cell phone tower electronics) they are
often swapped out for new oscillators as they get within the range of the
expected end-of-life. The large number of rubidium standards that turn up
on eBay is at least partly a result of this preventive maintenance program.
Most of the used standards likely will have limited life. However, their
low cost means you might be able to afford to buy more than one so you can
swap in one that works for one that has failed.

The standard I know that was designed with longer life in mind is the
Stanford Research Systems (SRS) line, Their PRS-10 model, for example, has
a design life of 20 years. Just look up the model for a description of the
long-term stability and low phase noise. The standard can monitor the lamp
start voltage as it rises as the rubidium depletes. These standards sell
for more on eBay because of the longer life and likelihood that they will
work for you even as used units. Some honest and knowledgable sellers can
tell you the lamp voltage. Disclosure: no financial connection with either
Ball-Efratom or PRS. I do own standards from both and I bought used ones on
eBay and they work (and are working after a couple of years) despite being
used units. On the other hand, I have some HP and Tracor/Sulzer quartz
frequency standards that are more than 20 (the HP) and 50 years old,
respectively. I’ve had to repair a couple of the Tracor units, but the
problem was almost always a transistor in the divider/amplifier stage that
failed. I also have a couple of Frequency Electronics quartz standards -
these are mil-spec units (URQ-10 and URQ-23) and work fine, but I’ve no
idea how long they were in service. They all have built-in battery packs
that are built up from “D” size nicad cells (I think - the packs are
sealed) and all have failed. They run fine without the batteries - the
power supply does not use the battery pack as a filter.

Anyone interested in time and frequency should have a look at the Time Nuts
site:

http://leapsecond.com/time-nuts.htm

SteveH

On Mon, Jul 13, 2020 at 11:36 garp66 <@green> wrote:

Does anyone know how the PTB-100 Ball Efratom Rubidium standard performs &
compares
technically (data & experience), with any of the other available
frequency standards ?

(phase noise, etc...)

-- and how it ages ?

Is the PTB-100 still a useful, viable kit ?

thank you,
rick



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