Re: [time-nuts] Two types of GPDSO / Rubidium

[Bob kb8tq]

Hi

The gotcha is that (unless you have something very exotic) there *is* no one 
standard
for the lab. You may have a device that is quite good on phase noise at some 
offsets and
horrible for long term. You might have another device that is good medium term 
and also
pretty good for close in phase noise. Since a Cs is a primary standard, it will 
always win in
the “long term / free running” category. In the disciplined category a GPSDO 
will always 
come out the winner, if you wait long enough.

So if this is headed off in many directions, first step would be to set up a 
phase noise measurement 
system. Start comparing standards. Best to start with things you have more than 
one of. First 
approximation is that they each are just a bit better than the comparison of 
the two would indicate. 
Then start cross comparing devices. Eventually you will come up with “this one 
is best at these
offsets” sort of decision. Just how good it is …. time to buy another :). Why 
start with phase noise?
it is the quickest of the measurements to do. Start with gear that will handle 
the 10 MHz sort of 
frequency you now are dealing with. Expand the range as needed. Also be sure to 
watch the 
floor of your gear vs the measurement. You might need better gear :)

Next step would be to start looking at long term drift. That might start at 1 
second or it might start
a bit longer. Again it’s a compare similar to similar at first sort of thing. 
Then start doing cross comparisons. 
If you stick with ADEV measurements, you can more easily compare to published 
data. There also is
a body of ADEV data in various posts to Time Nuts and on web sites run by Time 
Nuts. ( The same is
true of phase noise).

Test gear wise, something like the TimePod or the new “Son of TimePod” would be 
a fun device to
play with. Neither one is in the “dirt cheap” category. They don’t seem to show 
up on eBay for < $200….
That’s not in any way a knock on the retail price of either device. There are 
other pieces of gear out there
that do way less and cost way more. 

Bob

> On Sep 26, 2019, at 11:46 AM, Taka Kamiya via time-nuts 
>  wrote:
> 
> Bob, et al.
> First, current line up of timing source:OCXODOCXOEfratom Rb of various 
> kindPRS-10GPSDO of various kindDatum FTS4040/AHP5071A high-performance (DEAD 
> tube)
> Time measurement gear:HP85132AHP5335AHP5370ATIC
> 
> My first and at most problem is, I don't know which one to trust and in what 
> circumstances.  They all settle around 10E-10 to 10E-12 but since nothing 
> stands out, (like Hydrogen Maser) I have no ways of knowing if the 
> drift/error/noise I see is coming from DUT or the clock source.  I need to 
> establish "the" lab standard which everything can be compared against.
> So what's my ultimate goal?  Just that.  There is no way for me to tell if I 
> will get into microwave or something else.  Either way, having one reliable 
> standard is a must.  I am aware, there is no such thing as "the" standard.  
> Various DUT and purpose calls for different standard.  It could be OCXO or 
> Maser.  But still, I need to characterize them to know how bad/good DUT is.
> NUT case is already taken care of.  I'm a certified NUT.
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
>On Thursday, September 26, 2019, 11:56:56 AM EDT, Bob kb8tq 
>  wrote:  
> 
> Hi
> 
> There are some “simple” answers to this:
> 
> 1) You can (and many of us do) set up to measure things yourself. For most 
> setups this means
> comparing devices, but indeed Time Nuts seem to have piles and piles of 
> devices. You can do this
> with shiny new gear (possibly for a lot of money), eBay versions of the same 
> stuff (hopefully for 
> less money) or with home brew / DIY gear. Phase noise and the various xDEV’s 
> (like ADEV) can 
> be measured this way. 
> 
> 2) You *do* need to figure out what the objective is. If it’s microwaves then 
> the test gear needs to 
> run to those frequencies. If it’s just 10 MHz then not so much. If you do 
> indeed anticipate having
> gear at the 1x10^-15 @1 sec level then your setup needs to be a bit fancier 
> than if “only” 1x10^-11 
> is what you are after. 
> 
> 3) If this is cost constrained, be realistic about the costs. It is *very* 
> easy to say “max $100” and then
> start talking about many thousands of dollars of gear. It is also easy to 
> start with a budget and have it 
> creep on and on and on. Even projects funded by national governments (with 
> far larger charge cards 
> than any of us have) hit limits in terms of costs. It is part of this at any 
> level. 
> 
> It’s easy to say that you are setting up a full lab. If so, a hydrogen maser 
> (possibly two or three of them)
> *could* be part of the mix. There *are* Time Nuts who have set up that way, 
> but very few of them. Short
> of setting up that way, you will be in a compromise situation. (Indeed even a 
> maser is a bit of a compromise
> compared to other more exotic gear). 

Re: [time-nuts] Two types of GPDSO / Rubidium

[Taka Kamiya via time-nuts]

Bob, et al.
First, current line up of timing source:OCXODOCXOEfratom Rb of various 
kindPRS-10GPSDO of various kindDatum FTS4040/AHP5071A high-performance (DEAD 
tube)
Time measurement gear:HP85132AHP5335AHP5370ATIC

My first and at most problem is, I don't know which one to trust and in what 
circumstances.  They all settle around 10E-10 to 10E-12 but since nothing 
stands out, (like Hydrogen Maser) I have no ways of knowing if the 
drift/error/noise I see is coming from DUT or the clock source.  I need to 
establish "the" lab standard which everything can be compared against.
So what's my ultimate goal?  Just that.  There is no way for me to tell if I 
will get into microwave or something else.  Either way, having one reliable 
standard is a must.  I am aware, there is no such thing as "the" standard.  
Various DUT and purpose calls for different standard.  It could be OCXO or 
Maser.  But still, I need to characterize them to know how bad/good DUT is.
NUT case is already taken care of.  I'm a certified NUT.

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Thursday, September 26, 2019, 11:56:56 AM EDT, Bob kb8tq  
wrote:  
 
 Hi

There are some “simple” answers to this:

1) You can (and many of us do) set up to measure things yourself. For most 
setups this means
comparing devices, but indeed Time Nuts seem to have piles and piles of 
devices. You can do this
with shiny new gear (possibly for a lot of money), eBay versions of the same 
stuff (hopefully for 
less money) or with home brew / DIY gear. Phase noise and the various xDEV’s 
(like ADEV) can 
be measured this way. 

2) You *do* need to figure out what the objective is. If it’s microwaves then 
the test gear needs to 
run to those frequencies. If it’s just 10 MHz then not so much. If you do 
indeed anticipate having
gear at the 1x10^-15 @1 sec level then your setup needs to be a bit fancier 
than if “only” 1x10^-11 
is what you are after. 

3) If this is cost constrained, be realistic about the costs. It is *very* easy 
to say “max $100” and then
start talking about many thousands of dollars of gear. It is also easy to start 
with a budget and have it 
creep on and on and on. Even projects funded by national governments (with far 
larger charge cards 
than any of us have) hit limits in terms of costs. It is part of this at any 
level. 

It’s easy to say that you are setting up a full lab. If so, a hydrogen maser 
(possibly two or three of them)
*could* be part of the mix. There *are* Time Nuts who have set up that way, but 
very few of them. Short
of setting up that way, you will be in a compromise situation. (Indeed even a 
maser is a bit of a compromise
compared to other more exotic gear). Some degree of focus will be needed. Few 
of us have a really good
handle on that “focus” thing …..:)

Another wrinkle to this is that there are indeed measurements and terminology 
that are a bit unique to
the field. Indeed the measurements and gear that were common in the 1950’s have 
evolved into something
a bit different today. The same is true if you go back into the 1930’s. 
Different disciplines focus on different 
measures, even today. Tying papers, spec sheets, or measurements from one era 
or discipline to another 
can be challenging. There is no one universal single number that measures 
“best”. 

So yes, it’s complicated and it *can* be confusing. Welcome to why it’s called 
Time Nuts :)

Bob

> On Sep 26, 2019, at 1:29 AM, Taka Kamiya via time-nuts 
>  wrote:
> 
> Tom,
> I know you are absolutely right.  When I buy from eBay, I have no idea where 
> they came from.  Reject pile, junk yard, or pristine clean room.  
> Unfortunately, I can afford up to certain amount.  I have lots of PRS10 but 
> their origin is unknown.  Even if I buy 5065A, origin will be unknown and so 
> as condition.  Recently, I called around local cal-lab to see who can help me 
> validate these devices.  No one could.  I'm very tempted to buy T-bolt or 
> PRS10 new but at $1500, it's quite hefty.  I may just have to.
> I'm at learn as much as I can stage.  I have a Cesium but it's old.  4040/A  
> I have no idea how it was used or stored.  It would be nice to have one known 
> good standard.  The best I can do for now is my array of GPSDOs.  (from 
> unknown sources)
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
>    On Thursday, September 26, 2019, 3:05:19 AM EDT, Tom Van Baak 
> wrote:  
> 
> It might be a bit of an over-simplification to split oscillators in 
> those two camps, "fixed" and "agile". There are often many trade-offs in 
> performance that you have to deal with. Moreover if you are getting your 
> oscillators from eBay, or especially parts from China, you may also have 
> to assume that original factory specs are no longer valid.
> 
> This is one reason why the time nuts list is so preoccupied with making 
> accurate measurements of frequency standards. You only know what 

Re: [time-nuts] Two types of GPDSO / Rubidium

[Didier Juges]

I have a number of revisions of the John Vig tutorial in my Manual pages.
The most recent was sent to me directly by John but I am not sure if it has
the notes.
www.ko4bb.com
Go to Manuals and search for Vig

Didier KO4BB

On Thu, Sep 26, 2019 at 7:03 AM Chris Caudle  wrote:

> On Wed, September 25, 2019 5:45 pm, Taka Kamiya via time-nuts wrote:
> > discussions take place both for GPSDO with Crystal Oscillators and
> > Rubidium modules.  It appears there are two types of each.
> > 1)  fixed frequency type (less jitter)
> > 2)  frequency agile type (more jitter)
>
> That is a bit oversimplified.  GPSDO is "GPS disciplined oscillator,"
> meaning that the output frequency of the oscillator is forced to follow
> the inverse of the time measurements derived from the Global Positioning
> System.
> Obviously if the oscillator has to follow another reference it cannot
> truly be fixed frequency on the output, but there are various different
> ways that the frequency can be varied.  Depending on the important
> parameters for your needs the differences in mechanism may or may not be
> important.
>
> > I've read frequency agile Rb modules (ones you can change output
> > frequency) is one kind of Rb (sa.22c and fe5650, etc), and there is
> > another one that you cannot change frequency. (ie. T-bolt, PRS10, etc).
>
> You are mixing different types of equipment together, so it is a little
> difficult to know what you are asking.
> FE5650, PRS10 and SA.22C are rubidium frequency standards.  A rubidium
> frequency standard is fundamentally an OCXO which is slaved in a frequency
> lock loop to a way to measure atomic transitions in rubidium vapor.  There
> are various systematic errors which pull the frequency of that atomic
> transition measurement, so a rubidium standard will commonly have an
> adjustment mechanism that can adjust the output frequency far enough to
> compensate for those systematic errors, but you need a more accurate
> device for comparison for that adjustment to be worthwhile.
>
> A Thunderbolt is a complete GPS disciplined oscillator system which
> accepts GPS signals from an antenna, and outputs 10MHz which is slaved so
> that on average there are always 10 million output transitions per
> GPS-derived second estimation, and outputs a pulse once per second which
> occurs on  the transition of the GPS-derived second estimation.
>
> When the GPS signal is not available for some reason (antenna failure, GPS
> system problems, etc.) the GPS disciplined oscillator has to run in
> undisciplined mode.  Over that time the corrections to the oscillator
> frequency are not available, so only the intrinsic stability of the
> oscillator used sets the long term stability of the output frequency.  In
> that particular case (no GPS available) a GPSDO using a rubidium
> controlled oscillator as part of the design will have more  stable long
> term frequency than an oven quartz oscillator.
> While GPS signal is available to measure and control the output frequency
> there is little difference between an ovenized quartz and a rubidium
> controlled (which recall also has an ovenized quartz oscillator driving
> the output, but has a control loop using rubidium vapor transitions to
> correct any frequency drift of the quartz oscillator).
>
> > Words like phase noise and PLL are thrown out often in discussions.
>
> A very good place to start is searching for John Vig oscillator tutorial.
> John Vig has a lengthy presentation about all things relating to
> oscillators, if you can find the version which includes the notes along
> with the presentation slides you can spend a couple of days studying that
>
> > Is this because frequency agile type has the ultimate output from PLL
> > (subject to jitter) and fixed frequency type is from OCXO?
>
> Mixing different types of things into a single question again.
> The term PLL is phase locked loop, it is a particular type of control loop
> design which measures the edge transitions of a reference frequency input,
> the edge transitions of an output signal, and controls the output so that
> the edges match the reference.
> You can phase lock quartz, rubidium, pendulum.   Maybe an hour glass, but
> the only transition I can think of is when you turn the hour glass over,
> so that  would be an impractical PLL.
>
> > Even in main well known brands, I understand PRS10
> > and sa.22C and fe5650 are fundamentally different.
> > I guess they are all "GPS disciplined" in some way
>
> No, SA.22C and FE5650 have no connection to GPS,  they are not GPS
> disciplined in any way as stand alone devices, but can be used as part of
> a full GPS disciplined oscillator design. The SA.22C has a
> pulse-per-second (PPS) input, so it can be connected to GPS, but that gets
> into a lot of secondary questions relating to how that PPS is derived and
> whether it helps or hurts overall stability.
>
> --
> Chris Caudle
>
>
>
> ___
> time-nuts mailing list -- 

Re: [time-nuts] Two types of GPDSO / Rubidium

[Chris Caudle]

On Wed, September 25, 2019 5:45 pm, Taka Kamiya via time-nuts wrote:
> discussions take place both for GPSDO with Crystal Oscillators and
> Rubidium modules.  It appears there are two types of each.
> 1)  fixed frequency type (less jitter)
> 2)  frequency agile type (more jitter)

That is a bit oversimplified.  GPSDO is "GPS disciplined oscillator,"
meaning that the output frequency of the oscillator is forced to follow
the inverse of the time measurements derived from the Global Positioning
System.
Obviously if the oscillator has to follow another reference it cannot
truly be fixed frequency on the output, but there are various different
ways that the frequency can be varied.  Depending on the important
parameters for your needs the differences in mechanism may or may not be
important.

> I've read frequency agile Rb modules (ones you can change output
> frequency) is one kind of Rb (sa.22c and fe5650, etc), and there is
> another one that you cannot change frequency. (ie. T-bolt, PRS10, etc).

You are mixing different types of equipment together, so it is a little
difficult to know what you are asking.
FE5650, PRS10 and SA.22C are rubidium frequency standards.  A rubidium
frequency standard is fundamentally an OCXO which is slaved in a frequency
lock loop to a way to measure atomic transitions in rubidium vapor.  There
are various systematic errors which pull the frequency of that atomic
transition measurement, so a rubidium standard will commonly have an
adjustment mechanism that can adjust the output frequency far enough to
compensate for those systematic errors, but you need a more accurate
device for comparison for that adjustment to be worthwhile.

A Thunderbolt is a complete GPS disciplined oscillator system which
accepts GPS signals from an antenna, and outputs 10MHz which is slaved so
that on average there are always 10 million output transitions per
GPS-derived second estimation, and outputs a pulse once per second which
occurs on  the transition of the GPS-derived second estimation.

When the GPS signal is not available for some reason (antenna failure, GPS
system problems, etc.) the GPS disciplined oscillator has to run in
undisciplined mode.  Over that time the corrections to the oscillator
frequency are not available, so only the intrinsic stability of the
oscillator used sets the long term stability of the output frequency.  In
that particular case (no GPS available) a GPSDO using a rubidium
controlled oscillator as part of the design will have more  stable long
term frequency than an oven quartz oscillator.
While GPS signal is available to measure and control the output frequency
there is little difference between an ovenized quartz and a rubidium
controlled (which recall also has an ovenized quartz oscillator driving
the output, but has a control loop using rubidium vapor transitions to
correct any frequency drift of the quartz oscillator).

> Words like phase noise and PLL are thrown out often in discussions.

A very good place to start is searching for John Vig oscillator tutorial.
John Vig has a lengthy presentation about all things relating to
oscillators, if you can find the version which includes the notes along
with the presentation slides you can spend a couple of days studying that

> Is this because frequency agile type has the ultimate output from PLL
> (subject to jitter) and fixed frequency type is from OCXO?

Mixing different types of things into a single question again.
The term PLL is phase locked loop, it is a particular type of control loop
design which measures the edge transitions of a reference frequency input,
the edge transitions of an output signal, and controls the output so that
the edges match the reference.
You can phase lock quartz, rubidium, pendulum.   Maybe an hour glass, but
the only transition I can think of is when you turn the hour glass over,
so that  would be an impractical PLL.

> Even in main well known brands, I understand PRS10
> and sa.22C and fe5650 are fundamentally different.
> I guess they are all "GPS disciplined" in some way

No, SA.22C and FE5650 have no connection to GPS,  they are not GPS
disciplined in any way as stand alone devices, but can be used as part of
a full GPS disciplined oscillator design. The SA.22C has a
pulse-per-second (PPS) input, so it can be connected to GPS, but that gets
into a lot of secondary questions relating to how that PPS is derived and
whether it helps or hurts overall stability.

-- 
Chris Caudle



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Re: [time-nuts] Two types of GPDSO / Rubidium

[Taka Kamiya via time-nuts]

Tom,
I know you are absolutely right.  When I buy from eBay, I have no idea where 
they came from.  Reject pile, junk yard, or pristine clean room.  
Unfortunately, I can afford up to certain amount.  I have lots of PRS10 but 
their origin is unknown.  Even if I buy 5065A, origin will be unknown and so as 
condition.  Recently, I called around local cal-lab to see who can help me 
validate these devices.  No one could.  I'm very tempted to buy T-bolt or PRS10 
new but at $1500, it's quite hefty.  I may just have to.
I'm at learn as much as I can stage.  I have a Cesium but it's old.  4040/A  I 
have no idea how it was used or stored.  It would be nice to have one known 
good standard.  The best I can do for now is my array of GPSDOs.  (from unknown 
sources)

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Thursday, September 26, 2019, 3:05:19 AM EDT, Tom Van Baak 
 wrote:  
 
 It might be a bit of an over-simplification to split oscillators in 
those two camps, "fixed" and "agile". There are often many trade-offs in 
performance that you have to deal with. Moreover if you are getting your 
oscillators from eBay, or especially parts from China, you may also have 
to assume that original factory specs are no longer valid.

This is one reason why the time nuts list is so preoccupied with making 
accurate measurements of frequency standards. You only know what you 
have if 1) you buy it new from a reputable company, or 2) when you buy 
it cheap and measure it yourself with reputable test equipment, or 3) 
you get it from a friend who has measured it for you.

If you're asking specifically about Rb, I think the data shows that hp 
5065A has best performance, followed by PRS10, followed by all the cheap 
telecom Rb. Sorry, I don't have plots or URL's handy at the moment to 
support this with real data. My main take-away is to start with your 
requirements, see which products / specs meet that, and if you're buying 
dirt cheap surplus, make your own measurements to validate your 
requirements.

/tvb


On 9/25/2019 3:45 PM, Taka Kamiya via time-nuts wrote:
> This is a cross post from EEVBLOG.  I'm hoping there is someone who's 
> familiar with this subject would help me out here.
> I am hoping someone can help me understand this.  I've seen similar 
> discussions take place both for GPSDO with Crystal Oscillators and Rubidium 
> modules.  It appears there are two types of each.
> 1)  fixed frequency type (less jitter)
> 2)  frequency agile type (more jitter)
>
> I've read frequency agile Rb modules (ones you can change output frequency) 
> is one kind of Rb (sa.22c and fe5650, etc), and there is another one that you 
> cannot change frequency. (ie. T-bolt, PRS10, etc).  Words like phase noise 
> and PLL are thrown out often in discussions.  I vaguely remember frequency 
> agile types are less suitable if ultimate in stability is needed such as 
> multiplying the output into GHz range.  This discussion was about 10GHz 
> transverter.
> Is this because frequency agile type has the ultimate output from PLL 
> (subject to jitter) and fixed frequency type is from OCXO?  If this is the 
> case, why frequency agile type even exist?  It's not like it can be used as a 
> VFO (on radio).
>
> I'm sorry this is SO vague but that's the reason for this post.  I need to 
> understand this.  There was a wiki page on this, but it doesn't go into this 
> discussion deep enough.
>
> Would someone help me gain knowledge in this?
>
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> ___
> time-nuts mailing list --time-nuts@lists.febo.com
> To unsubscribe, go 
> tohttp://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


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Re: [time-nuts] Two types of GPDSO / Rubidium

[Azelio Boriani]

Maybe that "GPS tamed" is literally translated from chinese for "GPS
disciplined". It is indeed the disciplining that gives personality to
the GPSDO. You can PLLize the OCXO's 10MHz or the PPS derived from the
OCXO's 10MHz and see different results on the 10MHz's stability and
accuracy. It seems that Chinese built GPSDOs are derived from the
BG7TBL's design, you can find performance data here:


On Thu, Sep 26, 2019 at 8:00 AM Taka Kamiya via time-nuts
 wrote:
>
> I also see terms like GPS tamed or PLL-GPS.
> https://www.ebay.com/itm/1pcs-PLL-GPSDO-10M-GPS-tamed-clocks/263392170249?hash=item3d53659109:g:1p0AAOSwH3haNo7c
> https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR12.TRC2.A0.H0.Xgps-pll.TRS0&_nkw=gps-pll&_sacat=0
> It is not at all clear which one is what type and how it is designed.
>
> Even in main well known brands, I understand PRS10 and sa.22C and fe5650 are 
> fundamentally different.
> I guess they are all "GPS disciplined" in some way but for a newbie, telling 
> one apart from the other and picking a suitable architecture for the purpose 
> is very difficult.
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>
>
> On Wednesday, September 25, 2019, 9:28:29 PM EDT, Bob kb8tq 
>  wrote:
>
>  Hi
>
> The first gotcah is that the distinction is not very clear. A TBolt varies 
> the frequency of
> the OCXO in the GPSDO. GPSDO’s that use Rb’s can and often do vary the 
> frequency.
>
> Indeed some devices use a DDS to generate an output rather than varying 
> something else.
> I suspect that is what you are bumping into. In some cases a DDS feeds a 
> cleanup loop or filter
>  that restricts the output range.
>
> If you are after low noise at 10 GHz, the multiplier chain needs to be 
> carefully designed. There
> is a lot more to it than you might think. The first and most basic question 
> would be “is it a fixed
> frequency output or tuned?”. From there you can head off in a number of 
> directions.
>
> If you need to be able to change frequency from 1 MHz to 10 GHz in a few 
> nanoseconds, then
> there is no alternative to using a DDS. If hat is part of the requirement 
> then you go from there. If
> you want only 10 GHz +/- 0.001Hz then there are other, more quiet / lower 
> spur ways to do the job.
>
> Indeed it goes on and on …..
>
> Bob
>
>
>
> > On Sep 25, 2019, at 4:45 PM, Taka Kamiya via time-nuts 
> >  wrote:
> >
> > This is a cross post from EEVBLOG.  I'm hoping there is someone who's 
> > familiar with this subject would help me out here.
> > I am hoping someone can help me understand this.  I've seen similar 
> > discussions take place both for GPSDO with Crystal Oscillators and Rubidium 
> > modules.  It appears there are two types of each.
> > 1)  fixed frequency type (less jitter)
> > 2)  frequency agile type (more jitter)
> >
> > I've read frequency agile Rb modules (ones you can change output frequency) 
> > is one kind of Rb (sa.22c and fe5650, etc), and there is another one that 
> > you cannot change frequency. (ie. T-bolt, PRS10, etc).  Words like phase 
> > noise and PLL are thrown out often in discussions.  I vaguely remember 
> > frequency agile types are less suitable if ultimate in stability is needed 
> > such as multiplying the output into GHz range.  This discussion was about 
> > 10GHz transverter.
> > Is this because frequency agile type has the ultimate output from PLL 
> > (subject to jitter) and fixed frequency type is from OCXO?  If this is the 
> > case, why frequency agile type even exist?  It's not like it can be used as 
> > a VFO (on radio).
> >
> > I'm sorry this is SO vague but that's the reason for this post.  I need to 
> > understand this.  There was a wiki page on this, but it doesn't go into 
> > this discussion deep enough.
> >
> > Would someone help me gain knowledge in this?
> >
> > ---
> > (Mr.) Taka Kamiya
> > KB4EMF / ex JF2DKG
> > ___
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Re: [time-nuts] Two types of GPDSO / Rubidium

[Tom Van Baak]

It might be a bit of an over-simplification to split oscillators in 
those two camps, "fixed" and "agile". There are often many trade-offs in 
performance that you have to deal with. Moreover if you are getting your 
oscillators from eBay, or especially parts from China, you may also have 
to assume that original factory specs are no longer valid.


This is one reason why the time nuts list is so preoccupied with making 
accurate measurements of frequency standards. You only know what you 
have if 1) you buy it new from a reputable company, or 2) when you buy 
it cheap and measure it yourself with reputable test equipment, or 3) 
you get it from a friend who has measured it for you.


If you're asking specifically about Rb, I think the data shows that hp 
5065A has best performance, followed by PRS10, followed by all the cheap 
telecom Rb. Sorry, I don't have plots or URL's handy at the moment to 
support this with real data. My main take-away is to start with your 
requirements, see which products / specs meet that, and if you're buying 
dirt cheap surplus, make your own measurements to validate your 
requirements.


/tvb


On 9/25/2019 3:45 PM, Taka Kamiya via time-nuts wrote:

This is a cross post from EEVBLOG.  I'm hoping there is someone who's familiar 
with this subject would help me out here.
I am hoping someone can help me understand this.  I've seen similar discussions 
take place both for GPSDO with Crystal Oscillators and Rubidium modules.  It 
appears there are two types of each.
1)  fixed frequency type (less jitter)
2)  frequency agile type (more jitter)

I've read frequency agile Rb modules (ones you can change output frequency) is 
one kind of Rb (sa.22c and fe5650, etc), and there is another one that you 
cannot change frequency. (ie. T-bolt, PRS10, etc).  Words like phase noise and 
PLL are thrown out often in discussions.  I vaguely remember frequency agile 
types are less suitable if ultimate in stability is needed such as multiplying 
the output into GHz range.  This discussion was about 10GHz transverter.
Is this because frequency agile type has the ultimate output from PLL (subject 
to jitter) and fixed frequency type is from OCXO?  If this is the case, why 
frequency agile type even exist?  It's not like it can be used as a VFO (on 
radio).

I'm sorry this is SO vague but that's the reason for this post.  I need to 
understand this.  There was a wiki page on this, but it doesn't go into this 
discussion deep enough.

Would someone help me gain knowledge in this?

---
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
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Re: [time-nuts] Two types of GPDSO / Rubidium

[Taka Kamiya via time-nuts]

I also see terms like GPS tamed or PLL-GPS.  
https://www.ebay.com/itm/1pcs-PLL-GPSDO-10M-GPS-tamed-clocks/263392170249?hash=item3d53659109:g:1p0AAOSwH3haNo7c
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR12.TRC2.A0.H0.Xgps-pll.TRS0&_nkw=gps-pll&_sacat=0
It is not at all clear which one is what type and how it is designed.  

Even in main well known brands, I understand PRS10 and sa.22C and fe5650 are 
fundamentally different.
I guess they are all "GPS disciplined" in some way but for a newbie, telling 
one apart from the other and picking a suitable architecture for the purpose is 
very difficult.
--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Wednesday, September 25, 2019, 9:28:29 PM EDT, Bob kb8tq  
wrote:  
 
 Hi

The first gotcah is that the distinction is not very clear. A TBolt varies the 
frequency of
the OCXO in the GPSDO. GPSDO’s that use Rb’s can and often do vary the 
frequency. 

Indeed some devices use a DDS to generate an output rather than varying 
something else. 
I suspect that is what you are bumping into. In some cases a DDS feeds a 
cleanup loop or filter
 that restricts the output range. 

If you are after low noise at 10 GHz, the multiplier chain needs to be 
carefully designed. There
is a lot more to it than you might think. The first and most basic question 
would be “is it a fixed
frequency output or tuned?”. From there you can head off in a number of 
directions. 

If you need to be able to change frequency from 1 MHz to 10 GHz in a few 
nanoseconds, then 
there is no alternative to using a DDS. If hat is part of the requirement then 
you go from there. If
you want only 10 GHz +/- 0.001Hz then there are other, more quiet / lower spur 
ways to do the job.

Indeed it goes on and on …..

Bob



> On Sep 25, 2019, at 4:45 PM, Taka Kamiya via time-nuts 
>  wrote:
> 
> This is a cross post from EEVBLOG.  I'm hoping there is someone who's 
> familiar with this subject would help me out here.
> I am hoping someone can help me understand this.  I've seen similar 
> discussions take place both for GPSDO with Crystal Oscillators and Rubidium 
> modules.  It appears there are two types of each.  
> 1)  fixed frequency type (less jitter)
> 2)  frequency agile type (more jitter)
> 
> I've read frequency agile Rb modules (ones you can change output frequency) 
> is one kind of Rb (sa.22c and fe5650, etc), and there is another one that you 
> cannot change frequency. (ie. T-bolt, PRS10, etc).  Words like phase noise 
> and PLL are thrown out often in discussions.  I vaguely remember frequency 
> agile types are less suitable if ultimate in stability is needed such as 
> multiplying the output into GHz range.  This discussion was about 10GHz 
> transverter.
> Is this because frequency agile type has the ultimate output from PLL 
> (subject to jitter) and fixed frequency type is from OCXO?  If this is the 
> case, why frequency agile type even exist?  It's not like it can be used as a 
> VFO (on radio).
> 
> I'm sorry this is SO vague but that's the reason for this post.  I need to 
> understand this.  There was a wiki page on this, but it doesn't go into this 
> discussion deep enough.
> 
> Would someone help me gain knowledge in this?
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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Re: [time-nuts] Two types of GPDSO / Rubidium

[Bob kb8tq]

Hi

The first gotcah is that the distinction is not very clear. A TBolt varies the 
frequency of
the OCXO in the GPSDO. GPSDO’s that use Rb’s can and often do vary the 
frequency. 

Indeed some devices use a DDS to generate an output rather than varying 
something else. 
I suspect that is what you are bumping into. In some cases a DDS feeds a 
cleanup loop or filter
 that restricts the output range. 

If you are after low noise at 10 GHz, the multiplier chain needs to be 
carefully designed. There
is a lot more to it than you might think. The first and most basic question 
would be “is it a fixed
frequency output or tuned?”. From there you can head off in a number of 
directions. 

If you need to be able to change frequency from 1 MHz to 10 GHz in a few 
nanoseconds, then 
there is no alternative to using a DDS. If hat is part of the requirement then 
you go from there. If
you want only 10 GHz +/- 0.001Hz then there are other, more quiet / lower spur 
ways to do the job.

Indeed it goes on and on …..

Bob



> On Sep 25, 2019, at 4:45 PM, Taka Kamiya via time-nuts 
>  wrote:
> 
> This is a cross post from EEVBLOG.  I'm hoping there is someone who's 
> familiar with this subject would help me out here.
> I am hoping someone can help me understand this.  I've seen similar 
> discussions take place both for GPSDO with Crystal Oscillators and Rubidium 
> modules.  It appears there are two types of each.  
> 1)  fixed frequency type (less jitter)
> 2)  frequency agile type (more jitter)
> 
> I've read frequency agile Rb modules (ones you can change output frequency) 
> is one kind of Rb (sa.22c and fe5650, etc), and there is another one that you 
> cannot change frequency. (ie. T-bolt, PRS10, etc).  Words like phase noise 
> and PLL are thrown out often in discussions.  I vaguely remember frequency 
> agile types are less suitable if ultimate in stability is needed such as 
> multiplying the output into GHz range.  This discussion was about 10GHz 
> transverter.
> Is this because frequency agile type has the ultimate output from PLL 
> (subject to jitter) and fixed frequency type is from OCXO?  If this is the 
> case, why frequency agile type even exist?  It's not like it can be used as a 
> VFO (on radio).
> 
> I'm sorry this is SO vague but that's the reason for this post.  I need to 
> understand this.  There was a wiki page on this, but it doesn't go into this 
> discussion deep enough.
> 
> Would someone help me gain knowledge in this?
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


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