[time-nuts] Ultra Stable Rb

Wed Apr 8 22:47:35 UTC 2020

Hi

The “conventional wisdom” is that the “big cell” Rb’s ( like the GPS Rb and the 
5065 )  *do* have a fundamental advantage. The 5065 design dates to the 60’s.
There are a lot of things that can be addressed there. PHK has a great set of 
observations on his web site looking into that. 

The “ultimate” Rb would likely be a large cell version. Various groups are working 
on tune up’s for things like the FRK. Things like compensation that simply
where not considered back in the day, may be rational today. How close this gets
you …. only time will tell. 

Best guess is that Rb’s and OCXO’s share some basic gotchas. Your design only
gets you just so far. Some percentage of the parts will be utterly rotten. Some 
percentage will be pretty amazing. There will be a significant group in the middle. 

Screening has *always* been a way to deal with this. If you are willing to run
through a few hundred samples to get less than 5 “good ones”, you can do pretty
crazy things. This is done on OCXO’s, I don’t know of any examples of it being
done on Rb’s. 

Bob

> On Apr 8, 2020, at 6:33 PM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> 
> Bob, what I' was getting at was: what do you do differently to make a
> stable Rb versus one
> that drifts a lot?  Never mind price issues.
> 
> Could one buy, say, a PRS-10, extract the physics package from it, then
> engineer a stable
> Rb with that as a core?
> 
> Dana
> 
> 
> On Wed, Apr 8, 2020 at 4:19 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> The GPS Rb’s are “couple million dollar” sort of devices. Once GPS is up
>> and running,
>> the order volume drops off. The idea was to branch out into the broader
>> military market.
>> The design of the FRK did not change in any way as the price “morphed”.
>> They simply
>> had been making a pretty healthy margin on the product.  What happened to
>> the RFS
>> in the years after I left … no idea.
>> 
>> Bob
>> 
>>> On Apr 8, 2020, at 4:32 PM, djl <djl at montana.com> wrote:
>>> 
>>> So it's Chinese engineering? Find something good that works, start
>> removing parts until it doesn't, put in the part last removed, and sell it?
>>> 
>>> My granddad worked for a guy in LA called Madman Muntz who made tv's
>> that way in the late 1940's. They worked. Sorta. For a while. If the signal
>> was strong enough.
>>> Voila! $X-$400
>>> 
>>> On 2020-04-08 13:51, Bob kb8tq wrote:
>>>> Hi
>>>> At the time EG&G had done the GPS Rb’s but not done any other
>>>> military parts. Some research showed that indeed the FRK went into
>>>> a variety of systems and the price was $X. (It varied a bit with
>> quantity)
>>>> Push the numbers around and look at this and that. The decision was made
>>>> that indeed if you could sell a few hundred to maybe a thousand a year
>> at
>>>> $X, it was a good thing. A design was done and (as noted earlier) it was
>>>> a good little device.
>>>> The fun part came with that $X pricing. Out comes a request for some few
>>>> hundred pieces to this or that organization. Bid $X, order goes down to
>> the
>>>> competition for X-$300. Next request for a few hundred, bid X-$400,
>> order
>>>> goes down to the other guy for X-$500. This step by step process goes on
>>>> for a year …. same result again and again.
>>>> At the end of that time period it was far less clear just *why* one
>> does up
>>>> an FRK like part ….
>>>> Bob
>>>>> On Apr 8, 2020, at 2:32 PM, djl <djl at montana.com> wrote:
>>>>> What a tease!!!!! OK, very well WHY???
>>>>> Don
>>>>> On 2020-04-08 08:04, Bob kb8tq wrote:
>>>>>> Hi
>>>>>> A few of the long running FRK’s ( in a very similar package …
>>>>>> hmmm ….. wonder why …. yes, I was there way back then
>>>>>> and know very well why :) ) have crazy good long term aging.
>>>>>> That said, I don’t think that I’ve seen a FRK quite this good.
>>>>>> Thanks for sharing !!!
>>>>>> Bob
>>>>>>> On Apr 8, 2020, at 9:45 AM, martyn at ptsyst.com wrote:
>>>>>>> Hi Guys,
>>>>>>> Just though you'd be interested in my prototype rubidium frequency
>> standard
>>>>>>> I made in the 1990's.
>>>>>>> http://www.ptsyst.com/RFS10-FrequencyDrift.pdf
>>>>>>> I have measured its frequency at random intervals for the past 18
>> years.
>>>>>>> Its never been adjusted and is just free running.
>>>>>>> It was turned off in 2005 and sent to a customer in Japan for a few
>> weeks,
>>>>>>> then returned and turned back on.
>>>>>>> For the past 18 years its stayed within plus/minus 3 x 10E-11.
>>>>>>> The overall linear drift is something like 1.85 x 10E-13 per month.
>>>>>>> This is not an advert.  There's no way any of our production units
>> are as
>>>>>>> good as this one, well I assume so as I've never measured any for 18
>> years
>>>>>>> continuous!
>>>>>>> Its now over 25 years old, have hardly ever been turned off.  Any
>> day I
>>>>>>> expect it to fail, but it keeps on running!!
>>>>>>> Regards
>>>>>>> Martyn
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>>>>> --
>>>>> Dr. Don Latham  AJ7LL
>>>>> PO Box 404, Frenchtown, MT, 59834
>>>>> VOX: 406-626-4304
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>>> --
>>> Dr. Don Latham  AJ7LL
>>> PO Box 404, Frenchtown, MT, 59834
>>> VOX: 406-626-4304
>>> 
>>> 
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