[time-nuts] What are people paying for Stanford PRS10 rubidium standards?

David Kirkby david.kirkby at onetel.net
Wed Apr 27 09:08:58 EDT 2005

Brian Kirby wrote:
> "On the bright side, that seller _does_ seem to know what he's doing, 
> and I've seen him on ebay for a long time, so I'd believe him when he 
> says that the oscillator is working perfectly."
> Rex reported the issues we had with the seller. I directly asked him 
> several questions about programming before buying the rubidium and he 
> pointed to links from the manufactuer and to TVB's site on the 5650.  
> They were not for the unit he sold.  

This seems a common thing - people selling things they little about, but 
claiming they do.

I see nothing wrong with selling something and saying "sorry we can't 
test this, as we don't have the knowledge" but when people claim to know 
all about it, and say how good it is, then it is annoying.

That said, I am suspicious when someone who sells a lot of test 
equipment claims not to know how to test something simple. If you sell 
sig gens and then have a frequency counter for auction and say you don't 
know how to test it, I am suspicous!! Any fool dealing in test equipment 
should be able to do basic tests on equipment - a bit more than "it 
powers up".

I had a long (many years) argument with another radio ham who advertised 
some 24kV diodes. See:


I do object to paying a lot in carrige to get items imported from the 
USA to the UK, only to find they are not what the seller claims they are.

US sellers are reluctant to pay the shipping charges back to them. But I 
personlly don't see why I should pay to ship something back I did not 
order. The diodes I ordered had completely *different* part numbers. The 
HP 10811A does not have the same part number as the 10811-60111, so why 
someone sells the latter, claiming it is the former, I do not know.

Would you expect to pay to ship a rubidium oscillator back if you 
ordered a cesium one?

> After returning the unit and 
> receiving another unit with the same symptoms, I got with Rex and he had 
> reverse engineered the unit and I was able to power it up and test it.  
> I went back to the seller about programming, as he said he had a friend 
> that knew how to program the units, and ask for an introduction to his 
> friend.  I never heard from him again.

Em, its a bit late for me now, as I have paid for the PRS10, although I 
think that is a pretty standard item. I guess a problem could occur if 
it was "a special" and is in some way non-standard.

I guess I could ask Stanford - they might refuse to say, but probably 
will confirm if the S/N is a standard item.

> I am currently working on a project to discipline a Efratom FRS-C with a 
> Motorola M12+ GPS receiver and Brooks Shera's GPS controller.  I had 
> previously reported some data on the project and basically the 
> disciplining is working but its degraded the short term stability of the 
> rubidium.  Brooks has programmed a PIC with a longer time constant for 
> me and it has improved some specs on MTIE, but the short term is still 
> down.  I am retesting with another filter mode "Alpha" and will report 
> the results back to him soon.

Cheers, I'll be very interested in that. The PRS10 does have a 1pps 
input, which could be driven directly from the GPS. It also has a 1pps 

This bit of the PRS10 manual might interest you (page 33 if you download 

"To facilites integration into systems which require very low aging, 
automatic calibration, or a traceable frequency standard, the PRS10 may 
be locked to an external 1ppps input

A second order digital PLL is used to lock the unit's frequecny (both 
the 10MHz and 1pps outputs) to an external 1pps input with time 
constants ranging from 256s to 65536s (about 4 minutes to 18 hours)"

> Basically we are in the process of fine tuning a PIC for my rubidium and 
> as everybody knows, it takes a little time to see the results.

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Dr. David Kirkby,

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/

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