Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi

The “gotcha” with compensated devices is that there can be interesting 
breakpoints or decoupling to the sensor. Those show up more if the compensation
is working very hard to get the job done. Put another way - if you start at 
1x10^-9/C 
and compensate to 1x10^-11/C that is very different than starting at 3x10^-11/C.
A pretty good Rb or DOCXO would be a 1x10^-10 -30 to +70 spec. That would get 
you
into the 1x10^-12/C range. A 1x10^-9 part over the same range would be a good 
single
oven or a lower spec Rb. One always needs to be careful with those sort of 
translations. 
They may be optimistic by a factor or 3 or 6 or ….

Bob 

> On Nov 26, 2017, at 7:38 PM, Mark Sims  wrote:
> 
> BTW, that is the temp sensitivity of the X72 rubidiums that I have tested...
> 
> --
> 
> Your OCXO may be happy at 1x10^-11 / C
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Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi

If you only run over 10% of the EFC range, you only gain 3 bits. If the 
objective is 
in the 22 bit vicinity, (maybe 20 maybe 22 …) you really don’t get enough bits 
at a 10% 
span. From a lot of years of playing with control loops, if you need 20 *good* 
bits, you better
have a few more than that in the design …. Indeed there are converters out 
there with 1/8
LSB performance. There also are a lot of them with “guaranteed monotonic” as 
the main spec.
In that case you may get 2 LSB of “jump” as you do this or that….

Indeed another alternative is to let the OCXO warm up for a month. Then adjust 
a pot to center
things up. Run a “fine range” ADC to keep it happy. Come back in three to nine 
months and 
tweak the pot again. The main risk is a power outage and waiting a few weeks to 
get things 
back up and running again. 

A lot of this depends on how much of an EFC range you have and how much aging 
you expect. 
If you have 4 PPM of EFC and expect 1x10^-9 per month that gets you a pretty 
small range. If
you have 5x10^-8 of EFC and expect 1x10^-9 per day, the entire EFC may not last 
you for very
long at all. 

Another factor is temperature. Your OCXO may be happy at 1x10^-11 / C. If your 
control circuit
is good at the 5x10^-10 / C level that may be ok or it may be a problem. Either 
way, your control
range needs to accommodate both the OCXO and the rest of the circuit on top of 
the aging. 

Bob

> On Nov 26, 2017, at 1:05 PM, Azelio Boriani  wrote:
> 
> ...and what about shrinking the 16bit over the fraction of the EFC
> range that, for example, the OCXO will be using for the next 5 years?
> 16bit over 10V are as 20 (a little less, OK) over 1V, if I can use my
> 16bit over 1V for the next 5 years, when the DAC will be near full
> scale I can "trim" the aging.
> 
> On Sun, Nov 26, 2017 at 6:25 PM, Bob kb8tq  wrote:
>> Hi
>> 
>> If you sum two DAC’s without any sort of feedback, you get problems when the
>> “coarse” dac is changed. You have no way to know the step size of the coarse
>> dac to (say) 20 bit precision.
>> 
>> As an example : If you are after 20 “good” bits, you might overlap
>> them at the 10 bit point on the coarse dac. That would give you 22 bits on 
>> the
>> summed output. It would give you enough extra bits to take care of any odd
>> things that might be going on. You only have 1/1024 of the total range before
>> you must tune the coarse dac. Even with a good set of parts, you *will* be
>> doing coarse tuning.
>> 
>> Bob
>> 
>>> On Nov 26, 2017, at 12:13 PM, Azelio Boriani  
>>> wrote:
>>> 
>>> Is summing a "fine tune" 16bit DAC and a "coarse tune" 16bit (or less)
>>> DAC with an op-amp not good enough?
>>> 
>>> On Sun, Nov 26, 2017 at 5:53 PM, Bob kb8tq  wrote:
 Hi
 
 Each time I’ve tried the method in the app note, there has been a tone in 
 the output
 spectrum at the sample rate of the ADC. I’ve never found a way to do the 
 grounding
 that eliminates it. The tone is large enough to show up as a spur on a 
 “typical” OCXO
 when it goes into the EFC port.
 
 Bob
 
> On Nov 26, 2017, at 8:56 AM, Ole Petter Rønningen  
> wrote:
> 
> I guess everyone has seen this, but Linear has a nice appnote «A 
> Standards Lab Grade 20-Bit DAC with 0.1ppm/°C Drift»
> 
> http://cds.linear.com/docs/en/application-note/an86f.pdf
> 
> Ole
> 
>> 26. nov. 2017 kl. 13:50 skrev Magnus Danielson 
>> :
>> 
>> Hi
>> 
>>> On 11/26/2017 02:26 PM, Attila Kinali wrote:
>>> Though, if you have a decent 16bit DAC and want to get to 18bit,
>>> that's fairly simple using delta-sigma modulation... if you can live
>>> with a low pass fillter after the DAC. But the DNL will be the limiting
>>> factor here (unless you use some special techniques) and the (absolute) 
>>> INL
>>> will not get better, for obvious reasons.
>> 
>> I needed 19 bit rather than 16 bit, so I implemented an interpolation 
>> scheme. A first degree sigma-delta would also be possible, but for low 
>> ratios what I did was more efficient.
>> 
>> A first degree sigma-delta is fairly simple thought.
>> 
>> The trick is that you want to push the noise high up so it becomes 
>> trivial to filter, then the filter will not be hard to design and won't 
>> be low enough to cause PLL instability and implementation troubles.
>> 
>> Cheers,
>> Magnus
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Re: [time-nuts] Next upgrade

[Bert Kehren via time-nuts]

As I said in my original post from our point of view there are only two  
reasons for a Rb time and 16 bits will do the job.  I would not do an OCXO  
with less than 22 bits if analog at all.
Bert Kehren
 
 
In a message dated 11/26/2017 8:56:51 A.M. Eastern Standard Time,  
opronnin...@gmail.com writes:

I guess  everyone has seen this, but Linear has a nice appnote «A Standards 
Lab Grade  20-Bit DAC with 0.1ppm/°C  Drift»

http://cds.linear.com/docs/en/application-note/an86f.pdf

Ole

>  26. nov. 2017 kl. 13:50 skrev Magnus Danielson  
:
> 
> Hi
> 
>>  On 11/26/2017 02:26 PM, Attila Kinali wrote:
>> Though, if you have a  decent 16bit DAC and want to get to 18bit,
>> that's fairly simple  using delta-sigma modulation... if you can live
>> with a low pass  fillter after the DAC. But the DNL will be the limiting
>> factor  here (unless you use some special techniques) and the (absolute) 
 INL
>> will not get better, for obvious reasons.
> 
> I  needed 19 bit rather than 16 bit, so I implemented an interpolation 
scheme. A  first degree sigma-delta would also be possible, but for low ratios 
what I did  was more efficient.
> 
> A first degree sigma-delta is fairly  simple thought.
> 
> The trick is that you want to push the noise  high up so it becomes 
trivial to filter, then the filter will not be hard to  design and won't be low 
enough to cause PLL instability and implementation  troubles.
> 
> Cheers,
> Magnus
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Re: [time-nuts] Next upgrade

[Bert Kehren via time-nuts]

We tried coarse and fine using a LTC 24 bit ADC for characterization but  
test time is prohibitive and all the data has to be stored, or do it 
dynamically  like Tbolt does, I suspect SRS does something like that on the 
OCXO 
they can  afford it since it looks like the do that through out the unit that 
is why you  can not just replace one board'
That is how the Japanese got in to the test equipment build sub par and  
test and store data while HP and others still focused on quality components 
now  every one does it even an EF5680.
Bert Kehren
 
 
In a message dated 11/26/2017 12:25:49 P.M. Eastern Standard Time,  
kb...@n1k.org writes:

Hi

If you sum two DAC’s without any sort of feedback, you  get problems when 
the
“coarse” dac is changed. You have no way to know the  step size of the 
coarse
dac to (say) 20 bit precision. 

As an  example : If you are after 20 “good” bits, you might overlap 
them at the  10 bit point on the coarse dac. That would give you 22 bits on 
the
summed  output. It would give you enough extra bits to take care of any odd 
things  that might be going on. You only have 1/1024 of the total range 
before
you  must tune the coarse dac. Even with a good set of parts, you *will* be 
 
doing coarse tuning.

Bob

> On Nov 26, 2017, at 12:13 PM,  Azelio Boriani  
wrote:
> 
> Is  summing a "fine tune" 16bit DAC and a "coarse tune" 16bit (or less)
>  DAC with an op-amp not good enough?
> 
> On Sun, Nov 26, 2017 at  5:53 PM, Bob kb8tq  wrote:
>> Hi
>>  
>> Each time I’ve tried the method in the app note, there has been a  tone 
in the output
>> spectrum at the sample rate of the ADC. I’ve  never found a way to do 
the grounding
>> that eliminates it. The tone  is large enough to show up as a spur on a “
typical” OCXO
>> when it  goes into the EFC port.
>> 
>> Bob
>>  
>>> On Nov 26, 2017, at 8:56 AM, Ole Petter Rønningen  
 wrote:
>>> 
>>> I guess  everyone has seen this, but Linear has a nice appnote «A 
Standards Lab Grade  20-Bit DAC with 0.1ppm/°C Drift»
>>> 
>>>  http://cds.linear.com/docs/en/application-note/an86f.pdf
>>>  
>>> Ole
>>> 
 26. nov. 2017 kl.  13:50 skrev Magnus Danielson  
:
 
  Hi
 
> On 11/26/2017 02:26 PM, Attila  Kinali wrote:
> Though, if you have a decent 16bit DAC  and want to get to 18bit,
> that's fairly simple using  delta-sigma modulation... if you can live
> with a low  pass fillter after the DAC. But the DNL will be the  
limiting
> factor here (unless you use some special  techniques) and the 
(absolute) INL
> will not get  better, for obvious reasons.
 
 I needed  19 bit rather than 16 bit, so I implemented an interpolation 
scheme. A first  degree sigma-delta would also be possible, but for low 
ratios what I did was  more efficient.
 
 A first degree  sigma-delta is fairly simple thought.
 
  The trick is that you want to push the noise high up so it becomes 
trivial to  filter, then the filter will not be hard to design and won't be 
low enough to  cause PLL instability and implementation troubles.
  
 Cheers,
 Magnus
  ___
 time-nuts  mailing list -- time-nuts@febo.com
 To unsubscribe, go to  
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  and follow the instructions there.
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Re: [time-nuts] Next upgrade

[Azelio Boriani]

...and what about shrinking the 16bit over the fraction of the EFC
range that, for example, the OCXO will be using for the next 5 years?
16bit over 10V are as 20 (a little less, OK) over 1V, if I can use my
16bit over 1V for the next 5 years, when the DAC will be near full
scale I can "trim" the aging.

On Sun, Nov 26, 2017 at 6:25 PM, Bob kb8tq  wrote:
> Hi
>
> If you sum two DAC’s without any sort of feedback, you get problems when the
> “coarse” dac is changed. You have no way to know the step size of the coarse
> dac to (say) 20 bit precision.
>
> As an example : If you are after 20 “good” bits, you might overlap
> them at the 10 bit point on the coarse dac. That would give you 22 bits on the
> summed output. It would give you enough extra bits to take care of any odd
> things that might be going on. You only have 1/1024 of the total range before
> you must tune the coarse dac. Even with a good set of parts, you *will* be
> doing coarse tuning.
>
> Bob
>
>> On Nov 26, 2017, at 12:13 PM, Azelio Boriani  
>> wrote:
>>
>> Is summing a "fine tune" 16bit DAC and a "coarse tune" 16bit (or less)
>> DAC with an op-amp not good enough?
>>
>> On Sun, Nov 26, 2017 at 5:53 PM, Bob kb8tq  wrote:
>>> Hi
>>>
>>> Each time I’ve tried the method in the app note, there has been a tone in 
>>> the output
>>> spectrum at the sample rate of the ADC. I’ve never found a way to do the 
>>> grounding
>>> that eliminates it. The tone is large enough to show up as a spur on a 
>>> “typical” OCXO
>>> when it goes into the EFC port.
>>>
>>> Bob
>>>
 On Nov 26, 2017, at 8:56 AM, Ole Petter Rønningen  
 wrote:

 I guess everyone has seen this, but Linear has a nice appnote «A Standards 
 Lab Grade 20-Bit DAC with 0.1ppm/°C Drift»

 http://cds.linear.com/docs/en/application-note/an86f.pdf

 Ole

> 26. nov. 2017 kl. 13:50 skrev Magnus Danielson 
> :
>
> Hi
>
>> On 11/26/2017 02:26 PM, Attila Kinali wrote:
>> Though, if you have a decent 16bit DAC and want to get to 18bit,
>> that's fairly simple using delta-sigma modulation... if you can live
>> with a low pass fillter after the DAC. But the DNL will be the limiting
>> factor here (unless you use some special techniques) and the (absolute) 
>> INL
>> will not get better, for obvious reasons.
>
> I needed 19 bit rather than 16 bit, so I implemented an interpolation 
> scheme. A first degree sigma-delta would also be possible, but for low 
> ratios what I did was more efficient.
>
> A first degree sigma-delta is fairly simple thought.
>
> The trick is that you want to push the noise high up so it becomes 
> trivial to filter, then the filter will not be hard to design and won't 
> be low enough to cause PLL instability and implementation troubles.
>
> Cheers,
> Magnus
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to 
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 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to 
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
 and follow the instructions there.
>>>
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Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi

If you sum two DAC’s without any sort of feedback, you get problems when the
“coarse” dac is changed. You have no way to know the step size of the coarse
dac to (say) 20 bit precision. 

As an example : If you are after 20 “good” bits, you might overlap 
them at the 10 bit point on the coarse dac. That would give you 22 bits on the
summed output. It would give you enough extra bits to take care of any odd 
things that might be going on. You only have 1/1024 of the total range before
you must tune the coarse dac. Even with a good set of parts, you *will* be 
doing coarse tuning.

Bob

> On Nov 26, 2017, at 12:13 PM, Azelio Boriani  wrote:
> 
> Is summing a "fine tune" 16bit DAC and a "coarse tune" 16bit (or less)
> DAC with an op-amp not good enough?
> 
> On Sun, Nov 26, 2017 at 5:53 PM, Bob kb8tq  wrote:
>> Hi
>> 
>> Each time I’ve tried the method in the app note, there has been a tone in 
>> the output
>> spectrum at the sample rate of the ADC. I’ve never found a way to do the 
>> grounding
>> that eliminates it. The tone is large enough to show up as a spur on a 
>> “typical” OCXO
>> when it goes into the EFC port.
>> 
>> Bob
>> 
>>> On Nov 26, 2017, at 8:56 AM, Ole Petter Rønningen  
>>> wrote:
>>> 
>>> I guess everyone has seen this, but Linear has a nice appnote «A Standards 
>>> Lab Grade 20-Bit DAC with 0.1ppm/°C Drift»
>>> 
>>> http://cds.linear.com/docs/en/application-note/an86f.pdf
>>> 
>>> Ole
>>> 
 26. nov. 2017 kl. 13:50 skrev Magnus Danielson 
 :
 
 Hi
 
> On 11/26/2017 02:26 PM, Attila Kinali wrote:
> Though, if you have a decent 16bit DAC and want to get to 18bit,
> that's fairly simple using delta-sigma modulation... if you can live
> with a low pass fillter after the DAC. But the DNL will be the limiting
> factor here (unless you use some special techniques) and the (absolute) 
> INL
> will not get better, for obvious reasons.
 
 I needed 19 bit rather than 16 bit, so I implemented an interpolation 
 scheme. A first degree sigma-delta would also be possible, but for low 
 ratios what I did was more efficient.
 
 A first degree sigma-delta is fairly simple thought.
 
 The trick is that you want to push the noise high up so it becomes trivial 
 to filter, then the filter will not be hard to design and won't be low 
 enough to cause PLL instability and implementation troubles.
 
 Cheers,
 Magnus
 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to 
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
 and follow the instructions there.
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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Re: [time-nuts] Next upgrade

[Azelio Boriani]

Is summing a "fine tune" 16bit DAC and a "coarse tune" 16bit (or less)
DAC with an op-amp not good enough?

On Sun, Nov 26, 2017 at 5:53 PM, Bob kb8tq  wrote:
> Hi
>
> Each time I’ve tried the method in the app note, there has been a tone in the 
> output
> spectrum at the sample rate of the ADC. I’ve never found a way to do the 
> grounding
> that eliminates it. The tone is large enough to show up as a spur on a 
> “typical” OCXO
> when it goes into the EFC port.
>
> Bob
>
>> On Nov 26, 2017, at 8:56 AM, Ole Petter Rønningen  
>> wrote:
>>
>> I guess everyone has seen this, but Linear has a nice appnote «A Standards 
>> Lab Grade 20-Bit DAC with 0.1ppm/°C Drift»
>>
>> http://cds.linear.com/docs/en/application-note/an86f.pdf
>>
>> Ole
>>
>>> 26. nov. 2017 kl. 13:50 skrev Magnus Danielson :
>>>
>>> Hi
>>>
 On 11/26/2017 02:26 PM, Attila Kinali wrote:
 Though, if you have a decent 16bit DAC and want to get to 18bit,
 that's fairly simple using delta-sigma modulation... if you can live
 with a low pass fillter after the DAC. But the DNL will be the limiting
 factor here (unless you use some special techniques) and the (absolute) INL
 will not get better, for obvious reasons.
>>>
>>> I needed 19 bit rather than 16 bit, so I implemented an interpolation 
>>> scheme. A first degree sigma-delta would also be possible, but for low 
>>> ratios what I did was more efficient.
>>>
>>> A first degree sigma-delta is fairly simple thought.
>>>
>>> The trick is that you want to push the noise high up so it becomes trivial 
>>> to filter, then the filter will not be hard to design and won't be low 
>>> enough to cause PLL instability and implementation troubles.
>>>
>>> Cheers,
>>> Magnus
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> ___
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>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>
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Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi

Each time I’ve tried the method in the app note, there has been a tone in the 
output 
spectrum at the sample rate of the ADC. I’ve never found a way to do the 
grounding
that eliminates it. The tone is large enough to show up as a spur on a 
“typical” OCXO
when it goes into the EFC port. 

Bob

> On Nov 26, 2017, at 8:56 AM, Ole Petter Rønningen  
> wrote:
> 
> I guess everyone has seen this, but Linear has a nice appnote «A Standards 
> Lab Grade 20-Bit DAC with 0.1ppm/°C Drift»
> 
> http://cds.linear.com/docs/en/application-note/an86f.pdf
> 
> Ole
> 
>> 26. nov. 2017 kl. 13:50 skrev Magnus Danielson :
>> 
>> Hi
>> 
>>> On 11/26/2017 02:26 PM, Attila Kinali wrote:
>>> Though, if you have a decent 16bit DAC and want to get to 18bit,
>>> that's fairly simple using delta-sigma modulation... if you can live
>>> with a low pass fillter after the DAC. But the DNL will be the limiting
>>> factor here (unless you use some special techniques) and the (absolute) INL
>>> will not get better, for obvious reasons.
>> 
>> I needed 19 bit rather than 16 bit, so I implemented an interpolation 
>> scheme. A first degree sigma-delta would also be possible, but for low 
>> ratios what I did was more efficient.
>> 
>> A first degree sigma-delta is fairly simple thought.
>> 
>> The trick is that you want to push the noise high up so it becomes trivial 
>> to filter, then the filter will not be hard to design and won't be low 
>> enough to cause PLL instability and implementation troubles.
>> 
>> Cheers,
>> Magnus
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
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Re: [time-nuts] Next upgrade

[Ole Petter Rønningen]

I guess everyone has seen this, but Linear has a nice appnote «A Standards Lab 
Grade 20-Bit DAC with 0.1ppm/°C Drift»

http://cds.linear.com/docs/en/application-note/an86f.pdf

Ole

> 26. nov. 2017 kl. 13:50 skrev Magnus Danielson :
> 
> Hi
> 
>> On 11/26/2017 02:26 PM, Attila Kinali wrote:
>> Though, if you have a decent 16bit DAC and want to get to 18bit,
>> that's fairly simple using delta-sigma modulation... if you can live
>> with a low pass fillter after the DAC. But the DNL will be the limiting
>> factor here (unless you use some special techniques) and the (absolute) INL
>> will not get better, for obvious reasons.
> 
> I needed 19 bit rather than 16 bit, so I implemented an interpolation scheme. 
> A first degree sigma-delta would also be possible, but for low ratios what I 
> did was more efficient.
> 
> A first degree sigma-delta is fairly simple thought.
> 
> The trick is that you want to push the noise high up so it becomes trivial to 
> filter, then the filter will not be hard to design and won't be low enough to 
> cause PLL instability and implementation troubles.
> 
> Cheers,
> Magnus
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Re: [time-nuts] Next upgrade

[Magnus Danielson]

Hi

On 11/26/2017 02:26 PM, Attila Kinali wrote:

Though, if you have a decent 16bit DAC and want to get to 18bit,
that's fairly simple using delta-sigma modulation... if you can live
with a low pass fillter after the DAC. But the DNL will be the limiting
factor here (unless you use some special techniques) and the (absolute) INL
will not get better, for obvious reasons.


I needed 19 bit rather than 16 bit, so I implemented an interpolation 
scheme. A first degree sigma-delta would also be possible, but for low 
ratios what I did was more efficient.


A first degree sigma-delta is fairly simple thought.

The trick is that you want to push the noise high up so it becomes 
trivial to filter, then the filter will not be hard to design and won't 
be low enough to cause PLL instability and implementation troubles.


Cheers,
Magnus
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Re: [time-nuts] Next upgrade

[Attila Kinali]

On Thu, 23 Nov 2017 13:18:35 -0500
Bert Kehren via time-nuts  wrote:

> There was recently discussion of the use of the LTC1655 which 
> is still my # 1  choice. What was not mentioned on the 1650 is that in needs 
> a external reference  discontinued and double ling the cost.

There is just a tad bit of catch here:
The LTC1655 has an order of magnitude higher noise, a factor 2-3 higher
tempco of an LTC1650+LTC6655, a factor 2 higher DNL and a factor 2 higher INL.
The LTC1650 is the better DAC. That's why it's more expensive.

Whether the increased performance is worth the money or not, depends
on the application.

While we are at it, I'd like to mention the LTC1821. It beats the LTC1650
in most parameters, including price. But it has an increadibly low
spec'ed noise (typ 20nV/sqrt(Hz) at full scale output)

> 18 bits would be nicer but we have not  found one affordable.

It seems that manufacturing gets too costly for anything beyond 16bit
(unless you cut off at 10Hz).

Though, if you have a decent 16bit DAC and want to get to 18bit,
that's fairly simple using delta-sigma modulation... if you can live
with a low pass fillter after the DAC. But the DNL will be the limiting
factor here (unless you use some special techniques) and the (absolute) INL
will not get better, for obvious reasons.

Attila Kinali


-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Next upgrade

[Bert Kehren via time-nuts]

A few comments I forgot.
Most Rb's can use a clean up loop, we are experimenting with Wenzel's 600  
second loop recently posted here. Exceptions are the HP 5065 the optical 
unit is  the source of the performance, Corby experimented with different OCXO, 
 performance remained the same. Loop time constant is 0.01 second. There is 
also  no way to improve PRS 10 performance it will stay at 2 E-12 because 
of DAC  resolution.On related subject Corby and I community regularly and he 
mentioned  in all his 5065 work he has never experienced a bad lamp!!
We focus our Rb work on FRK/M100 because next to the 5065 it has the  
largest cell and it is easy to work on. Focus right now is OCXO and reducing  
time constant. If positive results we may look at inserting an optical filter,  
Corby did experimented with it but forgot reducing the time constant. 
Bert Kehren
 
 
 
In a message dated 11/22/2017 7:26:57 P.M. Eastern Standard Time,  
k8yumdoo...@gmail.com writes:

For the  most part the SRS-10 is a nice choice, although I'd always be wary
of  buying a
used one.

My only real beefs are that the tuning  granularity is rather coarse, about
2E-12, and the
disciplining loop  seems to be a bit aggressive so that the poor oscillator
gets  jerked
around quite a bit by the GPS.  This makes for rather  ugly-looking plots of
time error
over time.

The above comments  are derived from about 3 years of operating one as a hot
emergency spare at  the Arecibo Observatory against the day when the H-maser
crashed  abruptly.  In this case the SRS-10 was embedded in an FS725 which  
we
bought new.

Dana


On Wed, Nov 22, 2017 at 4:16 PM,  Jerry Hancock  wrote:

> Three  questions:
>
> 1) Now that I’ve split my Lucent RFTG-U into a REF0  and REF1 unit with
> both supplying 10Mhz and 1PPS, is there a way to  combine the outputs or
> some other technique to improve the short  and/or long term performance?
>
> 2) I’ve become interested in  Rubidium Disciplined Oscillators recently 
and
> was now thinking of  purchasing one of the PRS-10 that I see on Ebay. If I
> did that and  replaced one of the DOCXOs from one of the Lucent boxes, 
what
> impact  would this have on the overall performance both with and without
> (when  in hold-over)?  Basically, is it worth the money to upgrade one  of
> the boxes to a Rubidium disciplined oscillator assuming the GPS  signal is
> rarely lost?
>
> 3) Figuring the PRS-10 will  cost around $250 when all is said and done, 
is
> there a better option  to improve my GPSDO system?
>
> I basically use the GPSDO as a  reference for any equipment that takes an
> input. I have no monetary  need for a reference, just an interest.
>
>  Thanks.
>
> Jerry
>
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Re: [time-nuts] Next upgrade

[Bert Kehren via time-nuts]

The Next upgrade has touched several subjects we deal with on a dayle  
basis. Allow mw to add my thoughts. First we are time nuts trying within our  
limits to advance time and frequency generation and measurement with 
affordable  resources. We are at least a factor four orders of magnitude behind 
 the 
big boys in performance and  combined available resources.
As a market we are to small potato's so products tailored to our needs are  
limited and are getting less. An example SRS FS740 a nice box but no help 
to get  past E-12. New GPSDO's for Telecom do not have 5 or 10 MHz output.
PRS-10 a nice Rb, originally intended for FRS replacement has ADC and DCA  
control limeting it to 2 E-12. I have one, have not said anything because I  
want to get rid of it.
The question of why Rb. For our work there are only two reasons. Not living 
 next to NIST the only precise frequency reference is GPS. To overcome its 
limits  you need long time averaging. Aging compared to a OCXO is orders of 
magnitude  less. Second because of aging and tuning range a 16 bit DAC will 
do the job.  There was recently discussion of the use of the LTC1655 which 
is still my # 1  choice. What was not mentioned on the 1650 is that in needs 
a external reference  discontinued and double ling the cost. 18 bits would 
be nicer but we have not  found one affordable. Using a modified Shera with 1 
E-14 steps yields a  range up to 6.4 E-10. We are presently running three 
Tbolts, standard, OSA 8600  and the Efratom M100 with 40 000 seconds and 6 
E-17 per uV direct C field drive  through a 10 K resistor. Temperature, 
pressure and some start up issues make it  a less desirable option.For 
temperature 
and pressure we have an interface board,  but automatic recovery after 
power or GPS loss is not there after two weeks.  That is why we keep going back 
to 1655/Shera. Going to 6 E-17 keeps the jumps we  all see below ! E-13. 
Attila recently caught up with me on my Europe trip at  Juerg's home in 
Switzerland and can tell you about all our projects. Using the  standard Tbolt 
we 
also showed him the consistent jumps with a Tracor 527E and a  Cesium 
reference.
Yes doing a Cesium GPSDO again with 1655/Shera is doable but the question  
has to be: is it necessary. I worked with Richard McCorkle on it 4 years 
ago.  The question is does it make sense. My HP5061B with the new smaller tube 
shows  no aging but my GPS measuring capabilities are limited to 1 E-12. We 
have  decided to monitor 1 pps from a Tbolt against a 1pps derived from our 
respective  Cs and if necessary manually adjust.. To do it with le least 
amount of equipment  we decided to take a PICTIC II a divider chain and a 
custom V drive  using USB stick and blue tooth monitoring low cost, no fan and 
low power. I  never built a PICTIC but did combine Richard's and my boards for 
cost reason.  Bill Riley did an extensive evaluation and recommended to 
consider 4 layers.  This was the first time I looked at the board. Richard used 
schematic  capture resulting in no ground plane and long ground runs not 
what you want when  you chase nsec. I took a look and decided 4 layers is not 
necessary but was able  to add a nice ground plane. I have boards of PICTIC, 
divider and V drive. Right  now we still have work to do on M100/FRK GPSDO 
and the high resolution Austron  counter. If some one wants to build a unit, 
please contact me off list, if I am  convinced you will do it, I will send 
you the boards free of charge.
Richard did a PICTIC III and was working on a 4 and I was working on a 5.  
Sadly contact with him has stopped, the last correspondence was two years 
ago,  he had fallen and broken some ribs and had prostate cancer. His last 
words  where, he would get back with me after health was back under control. I 
have  tried what I did with Brooks, send a letter with USPS which resulted  
in Brooks Wife responding, you know the details, no response from Fairbanks. 
Has  any one heard from Richard?  He did a lot of work for us, brilliant, I 
 would ask a question, because of the time zone the typical next day 
response was  working PIC code.
Bert Kehren
 
 
 
In a message dated 11/22/2017 7:26:57 P.M. Eastern Standard Time,  
k8yumdoo...@gmail.com writes:

For the  most part the SRS-10 is a nice choice, although I'd always be wary
of  buying a
used one.

My only real beefs are that the tuning  granularity is rather coarse, about
2E-12, and the
disciplining loop  seems to be a bit aggressive so that the poor oscillator
gets  jerked
around quite a bit by the GPS.  This makes for rather  ugly-looking plots of
time error
over time.

The above comments  are derived from about 3 years of operating one as a hot
emergency spare at  the Arecibo Observatory against the day when the H-maser
crashed  abruptly.  In this case the SRS-10 was embedded in an FS725 which  
we
bought new.

Dana


On Wed, Nov 22, 2017 at 4:16 PM,  Jerry Hancock  wrote:

> Three  questions:
>
> 1) Now 

Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi

Yes, the “has no GPS” box becomes the active device in a REF0 / REF1 pair. 
If a survey is involved, it can take a *long* time for things to sort out.

Bob

> On Nov 23, 2017, at 7:22 AM, Adrian Godwin  wrote:
> 
> Turns out is does work - Initially, when I linked them, both boxes had the
> standby light go out and the unmodified ref-0 (with no GPS receiver) showed
> Fault and No GPS.
> 
> So I assumed there was some problem that might be causing them to conflict
> over the interface, and unplugged it.
> 
> I've tried it again with more patience and after 10 minutes or so, the
> modified ref0 goes into standby and the one without a receiver has only the
> green ON light.  I guess that's working correctly :)
> 
> 
> 
> On Thu, Nov 23, 2017 at 12:23 AM, Jerry Hancock  wrote:
> 
>> Adrian, when you stated it didn’t work, what were the results?
>> 
>> I had mine running in HA mode, if you can call it that, because only one
>> has a GPS.  Actually now that I think about it, the separate but modified
>> REF0 and modified REF1, assuming separate power and antennas, is probably
>> closer to HA than the original application.  I have both mine running now
>> with Lady Heather tracking each and I’ve been playing around with
>> comparisons.  Now in my case, if either goes down for any reason the other
>> can take over.  I guess in order to make them truly HA, we would need a
>> diode or relay switched transfer to the active unit.
>> 
>> Jerry
>> 
>>> On Nov 22, 2017, at 4:10 PM, Adrian Godwin  wrote:
>>> 
>>> Yes, I cross-connected  the pins, but I didn't cut any short.
>>> 
>>> 
>>> 
>>> On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq  wrote:
>>> 
 Hi
 
 I have run a number of the REF0 / REF1 combos. They all seem to work
>> fine.
 The standard cable has some odd short pins on it. If you are not hot
 plugging
 the cable I don’t think they matter at all. If anything, the system is
 more reliable
 with a normal length pin on the connector.
 
 Bob
 
> On Nov 22, 2017, at 6:08 PM, Adrian Godwin 
>> wrote:
> 
> I've got several of the Ref 0 boxes but none of the Ref 1. I've added
>> an
> Oncore GPS receiver to one of them as per Peter Garde's notes and it
 works
> well.
> 
> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
> configuration. Not that I need an HA reference but just for interest.
 I've
> only had a quick look so far and found that connecting the two together
> with a 15-pin cable didn't work.
> 
> Has anyone looked into this ?
> 
> 
> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> 
>> 
>>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
>>> 
>>> Three questions:
>>> 
>>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit
>> with
>> both supplying 10Mhz and 1PPS, is there a way to combine the outputs
>> or
>> some other technique to improve the short and/or long term
>> performance?
>> 
>> You can monitor one against the other. Ideally you would want three
>> GPSDO’s and a
>> monitoring setup. That way you can figure out which of the three has
 gone
>> bad.
>> 
>>> 
>>> 2) I’ve become interested in Rubidium Disciplined Oscillators
>> recently
>> and was now thinking of purchasing one of the PRS-10 that I see on
 Ebay. If
>> I did that and replaced one of the DOCXOs from one of the Lucent
>> boxes,
>> what impact would this have on the overall performance both with and
>> without (when in hold-over)?
>> 
>> If you go into holdover, you are the exception. Most setups rarely go
 into
>> holdover. When they
>> do, it’s because a hurricane just went over the house. Generally
>> that’s
>> not when the focus is going
>> to be on timing experiments.
>> 
>>> Basically, is it worth the money to upgrade one of the boxes to a
>> Rubidium disciplined oscillator assuming the GPS signal is rarely
>> lost?
>> 
>> Not worth the money if you are only looking at holdover and have a
 typical
>> setup.
>> 
>>> 
>>> 3) Figuring the PRS-10 will cost around $250 when all is said and
>> done,
>> is there a better option to improve my GPSDO system?
>> 
>> 
>> Disciplining implies continuously correcting. Rb standards age much
>> less
>> than a typical
>> OCXO. Oddly enough their temperature stability may not be as good as a
>> high end
>> DOCXO. It is fairly common to try to stabilize the environment your
>> standards operate in.
>> To the extent you are successful this reduces the need to deal with
>> temperature.
>> 
>> The net effect is that disciplining an Rb at a rate (filter / control
 loop
>> / manual 

Re: [time-nuts] Next upgrade

[Adrian Godwin]

Turns out is does work - Initially, when I linked them, both boxes had the
standby light go out and the unmodified ref-0 (with no GPS receiver) showed
Fault and No GPS.

So I assumed there was some problem that might be causing them to conflict
over the interface, and unplugged it.

I've tried it again with more patience and after 10 minutes or so, the
modified ref0 goes into standby and the one without a receiver has only the
green ON light.  I guess that's working correctly :)



On Thu, Nov 23, 2017 at 12:23 AM, Jerry Hancock  wrote:

> Adrian, when you stated it didn’t work, what were the results?
>
> I had mine running in HA mode, if you can call it that, because only one
> has a GPS.  Actually now that I think about it, the separate but modified
> REF0 and modified REF1, assuming separate power and antennas, is probably
> closer to HA than the original application.  I have both mine running now
> with Lady Heather tracking each and I’ve been playing around with
> comparisons.  Now in my case, if either goes down for any reason the other
> can take over.  I guess in order to make them truly HA, we would need a
> diode or relay switched transfer to the active unit.
>
> Jerry
>
> > On Nov 22, 2017, at 4:10 PM, Adrian Godwin  wrote:
> >
> > Yes, I cross-connected  the pins, but I didn't cut any short.
> >
> >
> >
> > On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >> I have run a number of the REF0 / REF1 combos. They all seem to work
> fine.
> >> The standard cable has some odd short pins on it. If you are not hot
> >> plugging
> >> the cable I don’t think they matter at all. If anything, the system is
> >> more reliable
> >> with a normal length pin on the connector.
> >>
> >> Bob
> >>
> >>> On Nov 22, 2017, at 6:08 PM, Adrian Godwin 
> wrote:
> >>>
> >>> I've got several of the Ref 0 boxes but none of the Ref 1. I've added
> an
> >>> Oncore GPS receiver to one of them as per Peter Garde's notes and it
> >> works
> >>> well.
> >>>
> >>> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
> >>> configuration. Not that I need an HA reference but just for interest.
> >> I've
> >>> only had a quick look so far and found that connecting the two together
> >>> with a 15-pin cable didn't work.
> >>>
> >>> Has anyone looked into this ?
> >>>
> >>>
> >>> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:
> >>>
>  Hi
> 
> 
> 
> > On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
> >
> > Three questions:
> >
> > 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit
> with
>  both supplying 10Mhz and 1PPS, is there a way to combine the outputs
> or
>  some other technique to improve the short and/or long term
> performance?
> 
>  You can monitor one against the other. Ideally you would want three
>  GPSDO’s and a
>  monitoring setup. That way you can figure out which of the three has
> >> gone
>  bad.
> 
> >
> > 2) I’ve become interested in Rubidium Disciplined Oscillators
> recently
>  and was now thinking of purchasing one of the PRS-10 that I see on
> >> Ebay. If
>  I did that and replaced one of the DOCXOs from one of the Lucent
> boxes,
>  what impact would this have on the overall performance both with and
>  without (when in hold-over)?
> 
>  If you go into holdover, you are the exception. Most setups rarely go
> >> into
>  holdover. When they
>  do, it’s because a hurricane just went over the house. Generally
> that’s
>  not when the focus is going
>  to be on timing experiments.
> 
> > Basically, is it worth the money to upgrade one of the boxes to a
>  Rubidium disciplined oscillator assuming the GPS signal is rarely
> lost?
> 
>  Not worth the money if you are only looking at holdover and have a
> >> typical
>  setup.
> 
> >
> > 3) Figuring the PRS-10 will cost around $250 when all is said and
> done,
>  is there a better option to improve my GPSDO system?
> 
> 
>  Disciplining implies continuously correcting. Rb standards age much
> less
>  than a typical
>  OCXO. Oddly enough their temperature stability may not be as good as a
>  high end
>  DOCXO. It is fairly common to try to stabilize the environment your
>  standards operate in.
>  To the extent you are successful this reduces the need to deal with
>  temperature.
> 
>  The net effect is that disciplining an Rb at a rate (filter / control
> >> loop
>  / manual tweak) of less than
>  a few days actually makes the Rb worse. Coming up with software to
> “back
>  off” on the tuning is
>  not as simple as it might seem.
> 
>  This comes back to the fact that the GPS signal (or any of the sat
>  signals) are quite noisy. You
>  need to average them over a *long* 

Re: [time-nuts] Next upgrade

[Dana Whitlow]

I once did make a token attempt at tweaking the disciplining parameters in
that SRS-10, but seemed to be getting nowhere and gave up on the effort.

Dana

On Wed, Nov 22, 2017 at 8:12 PM, Mark Sims  wrote:

> The PRS-10 does have disciplining parameters that you can tweak.   But the
> documentation is rather spotty on how to go about choosing good values.
>
> Also, I doubt that putting a Rb in an OCXO Lucent box would work well.
>  Rb loop parameters (like time constant) are rather different for the two
> classes of oscillator.
>
> ---
>
> > the disciplining loop seems to be a bit aggressive so that the poor
> oscillator
> gets jerked around quite a bit by the GPS
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Re: [time-nuts] Next upgrade

[Jerry Hancock]

Based on all the input I think I am going to just save up my mad money for a 
Cesium and be done with it.  (Doubt I’ll ever be “done with it”).


> On Nov 22, 2017, at 6:12 PM, Mark Sims  wrote:
> 
> The PRS-10 does have disciplining parameters that you can tweak.   But the 
> documentation is rather spotty on how to go about choosing good values.
> 
> Also, I doubt that putting a Rb in an OCXO Lucent box would work well.   Rb 
> loop parameters (like time constant) are rather different for the two classes 
> of oscillator.
> 
> ---
> 
>> the disciplining loop seems to be a bit aggressive so that the poor 
>> oscillator
> gets jerked around quite a bit by the GPS
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Re: [time-nuts] Next upgrade

[Dana Whitlow]

For the most part the SRS-10 is a nice choice, although I'd always be wary
of buying a
used one.

My only real beefs are that the tuning granularity is rather coarse, about
2E-12, and the
disciplining loop seems to be a bit aggressive so that the poor oscillator
gets jerked
around quite a bit by the GPS.  This makes for rather ugly-looking plots of
time error
over time.

The above comments are derived from about 3 years of operating one as a hot
emergency spare at the Arecibo Observatory against the day when the H-maser
crashed abruptly.  In this case the SRS-10 was embedded in an FS725 which we
bought new.

Dana


On Wed, Nov 22, 2017 at 4:16 PM, Jerry Hancock  wrote:

> Three questions:
>
> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
> some other technique to improve the short and/or long term performance?
>
> 2) I’ve become interested in Rubidium Disciplined Oscillators recently and
> was now thinking of purchasing one of the PRS-10 that I see on Ebay. If I
> did that and replaced one of the DOCXOs from one of the Lucent boxes, what
> impact would this have on the overall performance both with and without
> (when in hold-over)?  Basically, is it worth the money to upgrade one of
> the boxes to a Rubidium disciplined oscillator assuming the GPS signal is
> rarely lost?
>
> 3) Figuring the PRS-10 will cost around $250 when all is said and done, is
> there a better option to improve my GPSDO system?
>
> I basically use the GPSDO as a reference for any equipment that takes an
> input. I have no monetary need for a reference, just an interest.
>
> Thanks.
>
> Jerry
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Next upgrade

[Jerry Hancock]

Adrian, when you stated it didn’t work, what were the results?  

I had mine running in HA mode, if you can call it that, because only one has a 
GPS.  Actually now that I think about it, the separate but modified REF0 and 
modified REF1, assuming separate power and antennas, is probably closer to HA 
than the original application.  I have both mine running now with Lady Heather 
tracking each and I’ve been playing around with comparisons.  Now in my case, 
if either goes down for any reason the other can take over.  I guess in order 
to make them truly HA, we would need a diode or relay switched transfer to the 
active unit.

Jerry

> On Nov 22, 2017, at 4:10 PM, Adrian Godwin  wrote:
> 
> Yes, I cross-connected  the pins, but I didn't cut any short.
> 
> 
> 
> On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> I have run a number of the REF0 / REF1 combos. They all seem to work fine.
>> The standard cable has some odd short pins on it. If you are not hot
>> plugging
>> the cable I don’t think they matter at all. If anything, the system is
>> more reliable
>> with a normal length pin on the connector.
>> 
>> Bob
>> 
>>> On Nov 22, 2017, at 6:08 PM, Adrian Godwin  wrote:
>>> 
>>> I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
>>> Oncore GPS receiver to one of them as per Peter Garde's notes and it
>> works
>>> well.
>>> 
>>> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
>>> configuration. Not that I need an HA reference but just for interest.
>> I've
>>> only had a quick look so far and found that connecting the two together
>>> with a 15-pin cable didn't work.
>>> 
>>> Has anyone looked into this ?
>>> 
>>> 
>>> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:
>>> 
 Hi
 
 
 
> On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
> 
> Three questions:
> 
> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
 both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
 some other technique to improve the short and/or long term performance?
 
 You can monitor one against the other. Ideally you would want three
 GPSDO’s and a
 monitoring setup. That way you can figure out which of the three has
>> gone
 bad.
 
> 
> 2) I’ve become interested in Rubidium Disciplined Oscillators recently
 and was now thinking of purchasing one of the PRS-10 that I see on
>> Ebay. If
 I did that and replaced one of the DOCXOs from one of the Lucent boxes,
 what impact would this have on the overall performance both with and
 without (when in hold-over)?
 
 If you go into holdover, you are the exception. Most setups rarely go
>> into
 holdover. When they
 do, it’s because a hurricane just went over the house. Generally that’s
 not when the focus is going
 to be on timing experiments.
 
> Basically, is it worth the money to upgrade one of the boxes to a
 Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
 
 Not worth the money if you are only looking at holdover and have a
>> typical
 setup.
 
> 
> 3) Figuring the PRS-10 will cost around $250 when all is said and done,
 is there a better option to improve my GPSDO system?
 
 
 Disciplining implies continuously correcting. Rb standards age much less
 than a typical
 OCXO. Oddly enough their temperature stability may not be as good as a
 high end
 DOCXO. It is fairly common to try to stabilize the environment your
 standards operate in.
 To the extent you are successful this reduces the need to deal with
 temperature.
 
 The net effect is that disciplining an Rb at a rate (filter / control
>> loop
 / manual tweak) of less than
 a few days actually makes the Rb worse. Coming up with software to “back
 off” on the tuning is
 not as simple as it might seem.
 
 This comes back to the fact that the GPS signal (or any of the sat
 signals) are quite noisy. You
 need to average them over a *long* time to get good performance. Rb’s
>> are
 enough better than
 a GPSDO OCXO that the time ranges really stretch out ….
 
> 
> I basically use the GPSDO as a reference for any equipment that takes
>> an
 input. I have no monetary need for a reference, just an interest.
 
 For most normal test equipment, a GPSDO output is “plenty good enough”.
>> As
 a source for fancy
 timing experiments … maybe not so much. As a phase noise reference or a
 spur free source for
 microwave games … also not the best way to go.
 
 Bob
 
 
> 
> Thanks.
> 
> Jerry
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to 

Re: [time-nuts] Next upgrade

[Adrian Godwin]

Yes, I cross-connected  the pins, but I didn't cut any short.



On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq  wrote:

> Hi
>
> I have run a number of the REF0 / REF1 combos. They all seem to work fine.
> The standard cable has some odd short pins on it. If you are not hot
> plugging
> the cable I don’t think they matter at all. If anything, the system is
> more reliable
> with a normal length pin on the connector.
>
> Bob
>
> > On Nov 22, 2017, at 6:08 PM, Adrian Godwin  wrote:
> >
> > I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
> > Oncore GPS receiver to one of them as per Peter Garde's notes and it
> works
> > well.
> >
> > But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
> > configuration. Not that I need an HA reference but just for interest.
> I've
> > only had a quick look so far and found that connecting the two together
> > with a 15-pin cable didn't work.
> >
> > Has anyone looked into this ?
> >
> >
> > On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >>
> >>
> >>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
> >>>
> >>> Three questions:
> >>>
> >>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
> >> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
> >> some other technique to improve the short and/or long term performance?
> >>
> >> You can monitor one against the other. Ideally you would want three
> >> GPSDO’s and a
> >> monitoring setup. That way you can figure out which of the three has
> gone
> >> bad.
> >>
> >>>
> >>> 2) I’ve become interested in Rubidium Disciplined Oscillators recently
> >> and was now thinking of purchasing one of the PRS-10 that I see on
> Ebay. If
> >> I did that and replaced one of the DOCXOs from one of the Lucent boxes,
> >> what impact would this have on the overall performance both with and
> >> without (when in hold-over)?
> >>
> >> If you go into holdover, you are the exception. Most setups rarely go
> into
> >> holdover. When they
> >> do, it’s because a hurricane just went over the house. Generally that’s
> >> not when the focus is going
> >> to be on timing experiments.
> >>
> >>> Basically, is it worth the money to upgrade one of the boxes to a
> >> Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
> >>
> >> Not worth the money if you are only looking at holdover and have a
> typical
> >> setup.
> >>
> >>>
> >>> 3) Figuring the PRS-10 will cost around $250 when all is said and done,
> >> is there a better option to improve my GPSDO system?
> >>
> >>
> >> Disciplining implies continuously correcting. Rb standards age much less
> >> than a typical
> >> OCXO. Oddly enough their temperature stability may not be as good as a
> >> high end
> >> DOCXO. It is fairly common to try to stabilize the environment your
> >> standards operate in.
> >> To the extent you are successful this reduces the need to deal with
> >> temperature.
> >>
> >> The net effect is that disciplining an Rb at a rate (filter / control
> loop
> >> / manual tweak) of less than
> >> a few days actually makes the Rb worse. Coming up with software to “back
> >> off” on the tuning is
> >> not as simple as it might seem.
> >>
> >> This comes back to the fact that the GPS signal (or any of the sat
> >> signals) are quite noisy. You
> >> need to average them over a *long* time to get good performance. Rb’s
> are
> >> enough better than
> >> a GPSDO OCXO that the time ranges really stretch out ….
> >>
> >>>
> >>> I basically use the GPSDO as a reference for any equipment that takes
> an
> >> input. I have no monetary need for a reference, just an interest.
> >>
> >> For most normal test equipment, a GPSDO output is “plenty good enough”.
> As
> >> a source for fancy
> >> timing experiments … maybe not so much. As a phase noise reference or a
> >> spur free source for
> >> microwave games … also not the best way to go.
> >>
> >> Bob
> >>
> >>
> >>>
> >>> Thanks.
> >>>
> >>> Jerry
> >>>
> >>> ___
> >>> time-nuts mailing list -- time-nuts@febo.com
> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/
> >> mailman/listinfo/time-nuts
> >>> and follow the instructions there.
> >>
> >> ___
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to https://www.febo.com/cgi-bin/
> >> mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
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> mailman/listinfo/time-nuts
> and follow the instructions there.
>

Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi

I have run a number of the REF0 / REF1 combos. They all seem to work fine. 
The standard cable has some odd short pins on it. If you are not hot plugging
the cable I don’t think they matter at all. If anything, the system is more 
reliable
with a normal length pin on the connector.

Bob 

> On Nov 22, 2017, at 6:08 PM, Adrian Godwin  wrote:
> 
> I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
> Oncore GPS receiver to one of them as per Peter Garde's notes and it works
> well.
> 
> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
> configuration. Not that I need an HA reference but just for interest. I've
> only had a quick look so far and found that connecting the two together
> with a 15-pin cable didn't work.
> 
> Has anyone looked into this ?
> 
> 
> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> 
>> 
>>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
>>> 
>>> Three questions:
>>> 
>>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
>> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
>> some other technique to improve the short and/or long term performance?
>> 
>> You can monitor one against the other. Ideally you would want three
>> GPSDO’s and a
>> monitoring setup. That way you can figure out which of the three has gone
>> bad.
>> 
>>> 
>>> 2) I’ve become interested in Rubidium Disciplined Oscillators recently
>> and was now thinking of purchasing one of the PRS-10 that I see on Ebay. If
>> I did that and replaced one of the DOCXOs from one of the Lucent boxes,
>> what impact would this have on the overall performance both with and
>> without (when in hold-over)?
>> 
>> If you go into holdover, you are the exception. Most setups rarely go into
>> holdover. When they
>> do, it’s because a hurricane just went over the house. Generally that’s
>> not when the focus is going
>> to be on timing experiments.
>> 
>>> Basically, is it worth the money to upgrade one of the boxes to a
>> Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
>> 
>> Not worth the money if you are only looking at holdover and have a typical
>> setup.
>> 
>>> 
>>> 3) Figuring the PRS-10 will cost around $250 when all is said and done,
>> is there a better option to improve my GPSDO system?
>> 
>> 
>> Disciplining implies continuously correcting. Rb standards age much less
>> than a typical
>> OCXO. Oddly enough their temperature stability may not be as good as a
>> high end
>> DOCXO. It is fairly common to try to stabilize the environment your
>> standards operate in.
>> To the extent you are successful this reduces the need to deal with
>> temperature.
>> 
>> The net effect is that disciplining an Rb at a rate (filter / control loop
>> / manual tweak) of less than
>> a few days actually makes the Rb worse. Coming up with software to “back
>> off” on the tuning is
>> not as simple as it might seem.
>> 
>> This comes back to the fact that the GPS signal (or any of the sat
>> signals) are quite noisy. You
>> need to average them over a *long* time to get good performance. Rb’s are
>> enough better than
>> a GPSDO OCXO that the time ranges really stretch out ….
>> 
>>> 
>>> I basically use the GPSDO as a reference for any equipment that takes an
>> input. I have no monetary need for a reference, just an interest.
>> 
>> For most normal test equipment, a GPSDO output is “plenty good enough”. As
>> a source for fancy
>> timing experiments … maybe not so much. As a phase noise reference or a
>> spur free source for
>> microwave games … also not the best way to go.
>> 
>> Bob
>> 
>> 
>>> 
>>> Thanks.
>>> 
>>> Jerry
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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Re: [time-nuts] Next upgrade

[Jerry Hancock]

The 15pin cable has to be cross-connected.  Maybe that is your problem?

The pin connections were posted not that long ago.  It is like 1-15; 2-14; 
3-13; 4-12; 5-11; 6-10; 7-9; 8-8; 9-7; 10-6;11-5; etc.


> On Nov 22, 2017, at 3:08 PM, Adrian Godwin  wrote:
> 
> I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
> Oncore GPS receiver to one of them as per Peter Garde's notes and it works
> well.
> 
> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
> configuration. Not that I need an HA reference but just for interest. I've
> only had a quick look so far and found that connecting the two together
> with a 15-pin cable didn't work.
> 
> Has anyone looked into this ?
> 
> 
> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> 
>> 
>>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
>>> 
>>> Three questions:
>>> 
>>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
>> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
>> some other technique to improve the short and/or long term performance?
>> 
>> You can monitor one against the other. Ideally you would want three
>> GPSDO’s and a
>> monitoring setup. That way you can figure out which of the three has gone
>> bad.
>> 
>>> 
>>> 2) I’ve become interested in Rubidium Disciplined Oscillators recently
>> and was now thinking of purchasing one of the PRS-10 that I see on Ebay. If
>> I did that and replaced one of the DOCXOs from one of the Lucent boxes,
>> what impact would this have on the overall performance both with and
>> without (when in hold-over)?
>> 
>> If you go into holdover, you are the exception. Most setups rarely go into
>> holdover. When they
>> do, it’s because a hurricane just went over the house. Generally that’s
>> not when the focus is going
>> to be on timing experiments.
>> 
>>> Basically, is it worth the money to upgrade one of the boxes to a
>> Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
>> 
>> Not worth the money if you are only looking at holdover and have a typical
>> setup.
>> 
>>> 
>>> 3) Figuring the PRS-10 will cost around $250 when all is said and done,
>> is there a better option to improve my GPSDO system?
>> 
>> 
>> Disciplining implies continuously correcting. Rb standards age much less
>> than a typical
>> OCXO. Oddly enough their temperature stability may not be as good as a
>> high end
>> DOCXO. It is fairly common to try to stabilize the environment your
>> standards operate in.
>> To the extent you are successful this reduces the need to deal with
>> temperature.
>> 
>> The net effect is that disciplining an Rb at a rate (filter / control loop
>> / manual tweak) of less than
>> a few days actually makes the Rb worse. Coming up with software to “back
>> off” on the tuning is
>> not as simple as it might seem.
>> 
>> This comes back to the fact that the GPS signal (or any of the sat
>> signals) are quite noisy. You
>> need to average them over a *long* time to get good performance. Rb’s are
>> enough better than
>> a GPSDO OCXO that the time ranges really stretch out ….
>> 
>>> 
>>> I basically use the GPSDO as a reference for any equipment that takes an
>> input. I have no monetary need for a reference, just an interest.
>> 
>> For most normal test equipment, a GPSDO output is “plenty good enough”. As
>> a source for fancy
>> timing experiments … maybe not so much. As a phase noise reference or a
>> spur free source for
>> microwave games … also not the best way to go.
>> 
>> Bob
>> 
>> 
>>> 
>>> Thanks.
>>> 
>>> Jerry
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] Next upgrade

[Adrian Godwin]

I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
Oncore GPS receiver to one of them as per Peter Garde's notes and it works
well.

But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
configuration. Not that I need an HA reference but just for interest. I've
only had a quick look so far and found that connecting the two together
with a 15-pin cable didn't work.

Has anyone looked into this ?


On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq  wrote:

> Hi
>
>
>
> > On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
> >
> > Three questions:
> >
> > 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
> some other technique to improve the short and/or long term performance?
>
> You can monitor one against the other. Ideally you would want three
> GPSDO’s and a
> monitoring setup. That way you can figure out which of the three has gone
> bad.
>
> >
> > 2) I’ve become interested in Rubidium Disciplined Oscillators recently
> and was now thinking of purchasing one of the PRS-10 that I see on Ebay. If
> I did that and replaced one of the DOCXOs from one of the Lucent boxes,
> what impact would this have on the overall performance both with and
> without (when in hold-over)?
>
> If you go into holdover, you are the exception. Most setups rarely go into
> holdover. When they
> do, it’s because a hurricane just went over the house. Generally that’s
> not when the focus is going
> to be on timing experiments.
>
> > Basically, is it worth the money to upgrade one of the boxes to a
> Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
>
> Not worth the money if you are only looking at holdover and have a typical
> setup.
>
> >
> > 3) Figuring the PRS-10 will cost around $250 when all is said and done,
> is there a better option to improve my GPSDO system?
>
>
> Disciplining implies continuously correcting. Rb standards age much less
> than a typical
> OCXO. Oddly enough their temperature stability may not be as good as a
> high end
> DOCXO. It is fairly common to try to stabilize the environment your
> standards operate in.
> To the extent you are successful this reduces the need to deal with
> temperature.
>
> The net effect is that disciplining an Rb at a rate (filter / control loop
> / manual tweak) of less than
> a few days actually makes the Rb worse. Coming up with software to “back
> off” on the tuning is
> not as simple as it might seem.
>
> This comes back to the fact that the GPS signal (or any of the sat
> signals) are quite noisy. You
> need to average them over a *long* time to get good performance. Rb’s are
> enough better than
> a GPSDO OCXO that the time ranges really stretch out ….
>
> >
> > I basically use the GPSDO as a reference for any equipment that takes an
> input. I have no monetary need for a reference, just an interest.
>
> For most normal test equipment, a GPSDO output is “plenty good enough”. As
> a source for fancy
> timing experiments … maybe not so much. As a phase noise reference or a
> spur free source for
> microwave games … also not the best way to go.
>
> Bob
>
>
> >
> > Thanks.
> >
> > Jerry
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Next upgrade

[Bob kb8tq]

Hi



> On Nov 22, 2017, at 5:16 PM, Jerry Hancock  wrote:
> 
> Three questions:
> 
> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with both 
> supplying 10Mhz and 1PPS, is there a way to combine the outputs or some other 
> technique to improve the short and/or long term performance?

You can monitor one against the other. Ideally you would want three GPSDO’s and 
a 
monitoring setup. That way you can figure out which of the three has gone bad. 

> 
> 2) I’ve become interested in Rubidium Disciplined Oscillators recently and 
> was now thinking of purchasing one of the PRS-10 that I see on Ebay. If I did 
> that and replaced one of the DOCXOs from one of the Lucent boxes, what impact 
> would this have on the overall performance both with and without (when in 
> hold-over)?  

If you go into holdover, you are the exception. Most setups rarely go into 
holdover. When they 
do, it’s because a hurricane just went over the house. Generally that’s not 
when the focus is going 
to be on timing experiments. 

> Basically, is it worth the money to upgrade one of the boxes to a Rubidium 
> disciplined oscillator assuming the GPS signal is rarely lost?

Not worth the money if you are only looking at holdover and have a typical 
setup. 

> 
> 3) Figuring the PRS-10 will cost around $250 when all is said and done, is 
> there a better option to improve my GPSDO system? 


Disciplining implies continuously correcting. Rb standards age much less than a 
typical 
OCXO. Oddly enough their temperature stability may not be as good as a high end 
DOCXO. It is fairly common to try to stabilize the environment your standards 
operate in.
To the extent you are successful this reduces the need to deal with 
temperature. 

The net effect is that disciplining an Rb at a rate (filter / control loop / 
manual tweak) of less than 
a few days actually makes the Rb worse. Coming up with software to “back off” 
on the tuning is
not as simple as it might seem. 

This comes back to the fact that the GPS signal (or any of the sat signals) are 
quite noisy. You 
need to average them over a *long* time to get good performance. Rb’s are 
enough better than 
a GPSDO OCXO that the time ranges really stretch out ….

> 
> I basically use the GPSDO as a reference for any equipment that takes an 
> input. I have no monetary need for a reference, just an interest.

For most normal test equipment, a GPSDO output is “plenty good enough”. As a 
source for fancy
timing experiments … maybe not so much. As a phase noise reference or a spur 
free source for 
microwave games … also not the best way to go.

Bob


> 
> Thanks.
> 
> Jerry
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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