[time-nuts] Did a member of time-nuts buy this?

Bob Camp kb8tq at n1k.org
Sun Dec 7 19:06:17 EST 2014


Hi

> On Dec 7, 2014, at 6:15 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
> On 7 Dec 2014 18:59, "Bob Camp" <kb8tq at n1k.org> wrote:
> 
>>> 
>>> There is always
>>> 
>>> http://www.geo-ship.com/
>>> 
>>> which searches all eBay sites except those that use obscure characters
>>> like China.
> 
>> Right, but now you need to put in every possible spelling of anything
> that might reference to what you could be looking for in all the possible
> languages, Next you sort through a few thousand hits a day…
>> 
>> Consider:
>> 
>> You are looking for a GPSDO. The guy on the other end calls it a
> “frequency tamer” and never mentions GPS or OCXO’s. He only talks about the
> part numbers used in the device. If you are lucky he does it in English. If
> you want all the possible hits, the words *might* not be next to each other.
>> 
>> Lots of fun.
>> 
>> Bob
> 
> Bob,
> 
> I think you are making it out to be much more difficult than it is.
> 
> First you say one has to search every eBay site. When I show that is not
> true,

What you showed is that you can use a wide range search tool rather than searches customized to each regional marketplace. My point is that there is a problem with that. 

> you now say one needs to search every possible mis spelling of
> anything of interest.

There are a variety of ways things like simple things like Cesium get spelled. Depending which side of the Atlantic you learned to spell, you might / might not call them mis spellings. For some reason people like to put an “a” in the perfectly good / properly spelled word Cesium.  If you use a wide range search, you need to include the whole range of terms and languages that *might* be used in those regions. 

> 
> I am sure we could all find lots of GPSDO's. Finding them on eBay is the
> easy bit.

…. which is my main point. A search that is broad enough to find everything of interest also brings in a monstrous amount of stuff that needs to be sorted through. A wide range tool with a wide open search simply means more stuff to go through manually. 

> Deciding on which to buy is somewhat harder.

If it’s good (what ever it is), you don’t have long to decide. T Bolts sell these days for $300 or so. If one gets listed for “buy it now / free ship” at $70 it will go quickly.  Having a few thousand hits to go through each day makes that process pretty tedious. A once a week sort is unlikely to do you a lot of good.

Run a search for “frequency standard” on a search tool and see what comes up. It’s a lot of hits, the vast majority of them have no relation at all to accurate frequency. In some cases, that’s the only search that turns up this stuff.  Even the valid hits will be 99% useless because they will be repeats of stuff you have looked at before. 

> 
> Anyway,  I might buy a Cs standard for a bit of fun, but I will not buy one
> with the intention of actually using it as a serious frequency standard.

Without a working tube, they are not terribly interesting to play with. Reading the manual (free download) is more fun. 

Finding one on eBay for $1K that is “money back guaranteed works" these days is doing very well. More typical working prices are in the > $4K range. If you go HP 5071, the prices are going to be higher than a 5061. FTS versions are likely to be lower cost than HP’s with HP tubes. The FTS / Datum boxes are less likely to have all the lab bells and whistles on them. They are more likely to be adapted to telecom service. Either way, it’s a primary frequency standard. 

With a working tube, most Cs standards get sold when the beam current starts to drop / ADEV degrades. They go into yearly cal / checkup and get flagged. The company looks into the re-tube price and dumps the device. Since the “repair” is half the price of a brand new one, that’s always been a pretty common decision. Will it run for a month or a decade at "low current"? - who knows. 

This is a narrow field. You will spend a lot of time searching for a deal. 

Bob


> 
> Dave.
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