[time-nuts] Surplus Guidelines, was: Rubidium Standard

Rob Kimberley time.bandit at btinternet.com
Mon Dec 11 08:42:31 UTC 2006


Efratom bought by Ball and then sold to Datum. Datum bought by Symmetricom.
All units from the same pedigree. AFIK Gerhard Hubner one of the
co-designers of the first units still running things for Symmetricom in his
office south of Munich.

Rob Kimberley 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David Forbes
Sent: 10 December 2006 21:40
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Surplus Guidelines, was: Rubidium Standard

Jason,

I'm no expert at these devices, but here's what I've learned in the last
year:

The Ball/Efratom FRK is the oldest design that's commonly available. 
They work, but are likely to be out of range and may have little life left
in the physics package. Old-fashioned thru-hole PC boards, easy to work on.
The manual is available on the web as a free PDF file.

The Ball/Efratom FRS comes in several flavors: A, B, C, N etc. It's a more
modern packaging of the basic FRK design, but is very tightly packed in the
box so is harder to work on. The stability specs aren't real good, either.
The manual for these is also free on the web. Look for a recent date code -
I think they were manufactured up until 10 years ago or so.

The Datum/Symmetricom LPRO is a newer design and microprocessor controlled.
Probably a good investment if it's recently manufactured.

The SRS PRS-10 is a very modern, microprocessor controlled version with a
superior physics package and the ability to train onto a GPS-provided 1PPS
signal. They sell for way more than the others, for good reason - they're
designed to last for several decades.

Tom Van Baak has compared the stability of some of these devices... 
see the chart at the bottom of the page.
http://www.leapsecond.com/museum/lpro/

There are also some OEM modules that appear on ebay in quantity, which have
an L shape to them. I haven't seen anyone post manuals for these, so they
may be hard to debug.

You will also find packaged Rb units with front panel, power supply, backup
batteries etc. They seem to sell for twice as much as the raw units. These
will contain either an FRK or FRS unit inside, typically.

The HP 5065A has a much higher quality physics package than Efratom's units,
from what I can discern. Which does you no good if it's worn out! They tend
to be at least 25 years old and are highly questionable as an investment at
that age.

>Second, since just about any of these type items on eBay are sold 
>'as-is', what is a reasonable price for some of these things? Prices 
>seem to vary with no rhyme or reason. I would like to get a Rubidium 
>standard one day, but I honestly don't know what a fair price would be 
>for some that I have seen.

If it works, a couple hundred dollars for a used FRS or FRK is reasonable. I
picked up a never-used FRS-N unit for $300 recently. 
There was a batch of them that sold with steadily decreasing prices from
$500 down to the $200 initial bid as the market (such as it is) got
saturated.

-- 

--David Forbes, Tucson, AZ
http://www.cathodecorner.com/

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