Re: [time-nuts] Rubidium freq standard - temperature

[Hal Murray]

je...@hanler.com said:
> I tried scoping some pins.  I see a few different levels and one pin has
> what looks like a clock signal with a period of about 4.2ms.  Other than
> that, hard to tell without a manual.

Some devices print out version info and such at power up.  If you are willing 
to power cycle one, you might learn something by putting a scope on a pin 
when you power cycle it.

You can probably tell input pins from output pins by connecting a pin to 
ground or power through a 10 K resistor.  (That's assuming that one of  the 
output pins is high so you can tell what power is.  Or just guess 5V since 
it's old enough.  Or poke around to see what you find.)

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Rubidium freq standard - temperature

[Jerry Hancock]

Mark, I agree.  I tried scoping some pins.  I see a few different levels and 
one pin has what looks like a clock signal with a period of about 4.2ms.  Other 
than that, hard to tell without a manual.

I know people went so far as to contact Perkin Elmer without luck, I had heard 
they had acquired EG

I wouldn’t mind sending one to someone that could do a better test on it.  I’ll 
play around with them if and when I get the TPLL setup working. 


> On Nov 30, 2017, at 9:39 PM, Mark Sims  wrote:
> 
> I doubt that it would be a direct mapping to a 9-pin serial connector.  And 
> probably would not be outputting anything unless prompted.  It might be 
> useful to scope the pins and see if anything looks like serial data.  Even if 
> it has a serial port, without some kind of manual, it is probably useless.
> 
> If it not  RS-232 compatible voltage tolerant and you connect a +/- V RS-232 
> signal into it you could burn something out.
> 
> ---
> 
>> I opened it up, JT1 has 9 pins. What are the odds? I think I have to hook 
>> something up to it and see if there is anything on 2 or 3, no?
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[time-nuts] Rubidium freq standard - temperature

[Mark Sims]

I doubt that it would be a direct mapping to a 9-pin serial connector.  And 
probably would not be outputting anything unless prompted.  It might be useful 
to scope the pins and see if anything looks like serial data.  Even if it has a 
serial port, without some kind of manual, it is probably useless.

If it not  RS-232 compatible voltage tolerant and you connect a +/- V RS-232 
signal into it you could burn something out.

---

> I opened it up, JT1 has 9 pins. What are the odds? I think I have to hook 
> something up to it and see if there is anything on 2 or 3, no?
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Re: [time-nuts] Rubidium freq standard - temperature

[Jerry Hancock]

I opened it up, JT1 has 9 pins. What are the odds? I think I have to hook 
something up to it and see if there is anything on 2 or 3, no?

> On Nov 30, 2017, at 7:35 PM, Jerry Hancock  wrote:
> 
> I see a jack labeled JT1.  It has about 8 pins I remember.  I wonder...
> 
> 
>> On Nov 30, 2017, at 7:11 PM, Mark Sims  wrote:
>> 
>> A lot Rb's from that era have TTL level serial interfaces that can drive 
>> most RS-232 ports directly.  The PRS-10, SRO100, and LPFRS are examples.
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Re: [time-nuts] Rubidium freq standard - temperature

[Jerry Hancock]

I see a jack labeled JT1.  It has about 8 pins I remember.  I wonder...


> On Nov 30, 2017, at 7:11 PM, Mark Sims  wrote:
> 
> A lot Rb's from that era have TTL level serial interfaces that can drive most 
> RS-232 ports directly.  The PRS-10, SRO100, and LPFRS are examples.
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[time-nuts] Rubidium freq standard - temperature

[Mark Sims]

A lot Rb's from that era have TTL level serial interfaces that can drive most 
RS-232 ports directly.  The PRS-10, SRO100, and LPFRS are examples.
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Re: [time-nuts] Rubidium freq standard - temperature

[paul swed]

Will forward tomorrow. Yes I recall my lamp voltage is also very good.

On Thu, Nov 30, 2017 at 8:41 PM, Jerry Hancock  wrote:

> Paul, send whatever you have to clist  at hanler
> (without the D) dot com
>
> Also, the caps we replaced were only 4 electrolytics.  3 x 470uf 25v and a
> 270uf at 16V.  I used a 330uf 25v for the later.
>
> I’ve seen them for like $30 Canadian.  I think they are inexpensive due to
> the failure of the caps, no rs232,  no docs, etc.  I get great lamp voltage
> on mine, all over 10V if that says anything.  They seem stable but I don’t
> have the test setup needed or much to compare them to except my GPSDOs.  I
> hope to have a Cesium standard by end of year and I am building the TPLL
> test set.  But it seemed like there was some decent work done on the
> physics package.  Looks like it was all assembled by hand, then taped-up,
> sealed twice and clamped.
>
> Thanks.
>
> Jerry
>
> > On Nov 30, 2017, at 5:24 PM, paul swed  wrote:
> >
> > Jerry
> > I have some dribs and drabs of details on the units I have. Happy to send
> > whatever I have to you directly. Suspect its to large for FEBO. What I
> can
> > tell is they must have been considered quite good and for military use. I
> > haven't run mine alot because I was concerned about the temp like you.
> Nor
> > have I really dug in. They just worked from day one.
> > Granted maybe better if I look at the caps. The good thing about the unit
> > is the connector is clearly labeled with the pin functions. So I was able
> > to operate them right out of the hamfest. As I recall these were very
> very
> > inexpensive.
> > Regards
> > Paul
> > WB8TSL
> >
> > On Thu, Nov 30, 2017 at 8:04 PM, Jerry Hancock  wrote:
> >
> >> Paul, The units Gilbert gave me were TS-RFS.  They are fairly large.
> The
> >> physics end is about 5”x2”x2" and overall length about 9”.  They lock
> >> pretty quickly now that I’ve replace the caps.  They can drive 50ohms
> >> pretty hard, outputting a square wave.  I’m thinking of bolting on some
> >> fins to the physics end. Just two points: 1) it would be nice to dial
> them
> >> in closer; and 2) I wish I had equipment to test them more accurately.
> I’m
> >> working on building one of the Tight PLL test sets to solve #2.  Gilbert
> >> suggested we look to see if we could tap into the field current somehow
> to
> >> set the frequency more accurately.
> >>
> >>
> >>> On Nov 30, 2017, at 3:44 PM, paul swed  wrote:
> >>>
> >>> Jerry
> >>> You have some EG RBs. Thats great news. Now I am not alone. I have 2
> >> also
> >>> that work. I have found little details on them.
> >>> That said I believe they are intended to be mounted on a heat sink. One
> >> end
> >>> surely looks like that whats would be done.
> >>> I believe mine are LCR-10-T. Might have to double check that.
> >>> Regards
> >>> Paul
> >>> WB8TSL
> >>>
> >>> On Thu, Nov 30, 2017 at 6:22 PM, Jerry Hancock 
> wrote:
> >>>
>  I was able to get all 5 of these EG Rubidium Frequency Standards
> >> running
>  by replacing the caps as another member found.  They have a large
> >> heatsink
>  on them, no fins, and are running at 43C.  Is that too hot?  Should I
> >> bolt
>  them down to a larger heatsink?  They consume a little over 9w after
> >> they
>  lock, about double that while warming up.
> 
>  The only other issue I see is that the 8bit frequency setting doesn’t
>  allow me to set the frequency closer than 5E-11.  I don’t know if this
> >> is
>  good for these units and RFS in general or not.
> 
>  Thanks.
> 
>  Jerry
> 
>  [/begin buttkissing]
> 
>  PS:  I have learned quite a bit from this group in the past couple of
>  months.  John Miles, Gilbert, Mark Sims, Bob, etc, etc have been a lot
> >> of
>  help and have added a lot of enjoyment to my hobby.
> 
>  [/end buttkissing]
> 
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Re: [time-nuts] Rubidium freq standard - temperature

[Jerry Hancock]

Paul, send whatever you have to clist  at hanler 
(without the D) dot com

Also, the caps we replaced were only 4 electrolytics.  3 x 470uf 25v and a 
270uf at 16V.  I used a 330uf 25v for the later.

I’ve seen them for like $30 Canadian.  I think they are inexpensive due to the 
failure of the caps, no rs232,  no docs, etc.  I get great lamp voltage on 
mine, all over 10V if that says anything.  They seem stable but I don’t have 
the test setup needed or much to compare them to except my GPSDOs.  I hope to 
have a Cesium standard by end of year and I am building the TPLL test set.  But 
it seemed like there was some decent work done on the physics package.  Looks 
like it was all assembled by hand, then taped-up, sealed twice and clamped.

Thanks.  

Jerry

> On Nov 30, 2017, at 5:24 PM, paul swed  wrote:
> 
> Jerry
> I have some dribs and drabs of details on the units I have. Happy to send
> whatever I have to you directly. Suspect its to large for FEBO. What I can
> tell is they must have been considered quite good and for military use. I
> haven't run mine alot because I was concerned about the temp like you. Nor
> have I really dug in. They just worked from day one.
> Granted maybe better if I look at the caps. The good thing about the unit
> is the connector is clearly labeled with the pin functions. So I was able
> to operate them right out of the hamfest. As I recall these were very very
> inexpensive.
> Regards
> Paul
> WB8TSL
> 
> On Thu, Nov 30, 2017 at 8:04 PM, Jerry Hancock  wrote:
> 
>> Paul, The units Gilbert gave me were TS-RFS.  They are fairly large.  The
>> physics end is about 5”x2”x2" and overall length about 9”.  They lock
>> pretty quickly now that I’ve replace the caps.  They can drive 50ohms
>> pretty hard, outputting a square wave.  I’m thinking of bolting on some
>> fins to the physics end. Just two points: 1) it would be nice to dial them
>> in closer; and 2) I wish I had equipment to test them more accurately.  I’m
>> working on building one of the Tight PLL test sets to solve #2.  Gilbert
>> suggested we look to see if we could tap into the field current somehow to
>> set the frequency more accurately.
>> 
>> 
>>> On Nov 30, 2017, at 3:44 PM, paul swed  wrote:
>>> 
>>> Jerry
>>> You have some EG RBs. Thats great news. Now I am not alone. I have 2
>> also
>>> that work. I have found little details on them.
>>> That said I believe they are intended to be mounted on a heat sink. One
>> end
>>> surely looks like that whats would be done.
>>> I believe mine are LCR-10-T. Might have to double check that.
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>>> On Thu, Nov 30, 2017 at 6:22 PM, Jerry Hancock  wrote:
>>> 
 I was able to get all 5 of these EG Rubidium Frequency Standards
>> running
 by replacing the caps as another member found.  They have a large
>> heatsink
 on them, no fins, and are running at 43C.  Is that too hot?  Should I
>> bolt
 them down to a larger heatsink?  They consume a little over 9w after
>> they
 lock, about double that while warming up.
 
 The only other issue I see is that the 8bit frequency setting doesn’t
 allow me to set the frequency closer than 5E-11.  I don’t know if this
>> is
 good for these units and RFS in general or not.
 
 Thanks.
 
 Jerry
 
 [/begin buttkissing]
 
 PS:  I have learned quite a bit from this group in the past couple of
 months.  John Miles, Gilbert, Mark Sims, Bob, etc, etc have been a lot
>> of
 help and have added a lot of enjoyment to my hobby.
 
 [/end buttkissing]
 
 ___
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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] Rubidium freq standard - temperature

[Jerry Hancock]

1) Model number is TS-RFS and they vary for series from A to H, assuming the 
series is linear as I only have 5 of them.
2) No manual.
3) There is an 8 bit dip switch with a maximum range of about 10mhz and a step 
of .39mhz. I might have these off by a factor of 10 but I was able to set two 
of mine to within 5E-11.  The dip is located near a micro of some kind but it 
is a resistive binary ladder that could be just positioned there.  If it is 
setting current then it would be easy to dial it closer I believe.
4) I don’t see a place for an RS232 output nor recognize any of the usual 
suspect drivers.


> On Nov 30, 2017, at 4:49 PM, Mark Sims  wrote:
> 
> 43C seems reasonable for the baseplate temperature.
> 
> What is the model number for these?   Do you have a manual?   How are you 
> setting the frequency?I just got in a Spectratime SRO100 and am adding 
> support for it to Lady Heather.   I may also do the LPFRS which may be 
> related to yours.
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Re: [time-nuts] Rubidium freq standard - temperature

[paul swed]

Jerry
I have some dribs and drabs of details on the units I have. Happy to send
whatever I have to you directly. Suspect its to large for FEBO. What I can
tell is they must have been considered quite good and for military use. I
haven't run mine alot because I was concerned about the temp like you. Nor
have I really dug in. They just worked from day one.
Granted maybe better if I look at the caps. The good thing about the unit
is the connector is clearly labeled with the pin functions. So I was able
to operate them right out of the hamfest. As I recall these were very very
inexpensive.
Regards
Paul
WB8TSL

On Thu, Nov 30, 2017 at 8:04 PM, Jerry Hancock  wrote:

> Paul, The units Gilbert gave me were TS-RFS.  They are fairly large.  The
> physics end is about 5”x2”x2" and overall length about 9”.  They lock
> pretty quickly now that I’ve replace the caps.  They can drive 50ohms
> pretty hard, outputting a square wave.  I’m thinking of bolting on some
> fins to the physics end. Just two points: 1) it would be nice to dial them
> in closer; and 2) I wish I had equipment to test them more accurately.  I’m
> working on building one of the Tight PLL test sets to solve #2.  Gilbert
> suggested we look to see if we could tap into the field current somehow to
> set the frequency more accurately.
>
>
> > On Nov 30, 2017, at 3:44 PM, paul swed  wrote:
> >
> > Jerry
> > You have some EG RBs. Thats great news. Now I am not alone. I have 2
> also
> > that work. I have found little details on them.
> > That said I believe they are intended to be mounted on a heat sink. One
> end
> > surely looks like that whats would be done.
> > I believe mine are LCR-10-T. Might have to double check that.
> > Regards
> > Paul
> > WB8TSL
> >
> > On Thu, Nov 30, 2017 at 6:22 PM, Jerry Hancock  wrote:
> >
> >> I was able to get all 5 of these EG Rubidium Frequency Standards
> running
> >> by replacing the caps as another member found.  They have a large
> heatsink
> >> on them, no fins, and are running at 43C.  Is that too hot?  Should I
> bolt
> >> them down to a larger heatsink?  They consume a little over 9w after
> they
> >> lock, about double that while warming up.
> >>
> >> The only other issue I see is that the 8bit frequency setting doesn’t
> >> allow me to set the frequency closer than 5E-11.  I don’t know if this
> is
> >> good for these units and RFS in general or not.
> >>
> >> Thanks.
> >>
> >> Jerry
> >>
> >> [/begin buttkissing]
> >>
> >> PS:  I have learned quite a bit from this group in the past couple of
> >> months.  John Miles, Gilbert, Mark Sims, Bob, etc, etc have been a lot
> of
> >> help and have added a lot of enjoyment to my hobby.
> >>
> >> [/end buttkissing]
> >>
> >> ___
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> >> mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >>
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Re: [time-nuts] Trimble Mini-T Timing Glitches

[jimlux]

On 11/30/17 3:05 PM, Leo Bodnar wrote:

Completely off-topic comment while on the subject:

I can't see how randomly selected 1ms of data can contain unambiguously 
detectable start of C/A code.
If NAV data bit phase flip occurred within this 1ms of data then correlation 
search will most probably fail.
Yes, the probability of this is only 5% (assuming equal number of 1s and 0s in 
NAV message) but still not zero.


I believe that Nav bits only flip at code epoch boundaries (actually, 
every 20 code epochs), it can't change in the middle of a 1023 chip 
sequence.  You use the epoch sync signal to run your symbol integrator.




Perhaps the quote should have added "carefully chosen 1ms of data"
At the minimum, one would typically select 2ms of sampled data when they are 
doing a correlation search and then they are guaranteed a full PRN sequence 
somewhere in there.

Leo


From: Tom Van Baak Thu, 30 Nov 2017 14:43:02 -0800
In order to find the beginning of a C/A code in the received signal only a
very limited data record is needed such as 1 ms. If there is no Doppler effect
on the received signal, then one millisecond of data contains all the 1,023
chips.


Doppler does make it harder (ask the folks who did the Huygens probe)





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Re: [time-nuts] Rubidium freq standard - temperature

[Jerry Hancock]

Paul, The units Gilbert gave me were TS-RFS.  They are fairly large.  The 
physics end is about 5”x2”x2" and overall length about 9”.  They lock pretty 
quickly now that I’ve replace the caps.  They can drive 50ohms pretty hard, 
outputting a square wave.  I’m thinking of bolting on some fins to the physics 
end. Just two points: 1) it would be nice to dial them in closer; and 2) I wish 
I had equipment to test them more accurately.  I’m working on building one of 
the Tight PLL test sets to solve #2.  Gilbert suggested we look to see if we 
could tap into the field current somehow to set the frequency more accurately.


> On Nov 30, 2017, at 3:44 PM, paul swed  wrote:
> 
> Jerry
> You have some EG RBs. Thats great news. Now I am not alone. I have 2 also
> that work. I have found little details on them.
> That said I believe they are intended to be mounted on a heat sink. One end
> surely looks like that whats would be done.
> I believe mine are LCR-10-T. Might have to double check that.
> Regards
> Paul
> WB8TSL
> 
> On Thu, Nov 30, 2017 at 6:22 PM, Jerry Hancock  wrote:
> 
>> I was able to get all 5 of these EG Rubidium Frequency Standards running
>> by replacing the caps as another member found.  They have a large heatsink
>> on them, no fins, and are running at 43C.  Is that too hot?  Should I bolt
>> them down to a larger heatsink?  They consume a little over 9w after they
>> lock, about double that while warming up.
>> 
>> The only other issue I see is that the 8bit frequency setting doesn’t
>> allow me to set the frequency closer than 5E-11.  I don’t know if this is
>> good for these units and RFS in general or not.
>> 
>> Thanks.
>> 
>> Jerry
>> 
>> [/begin buttkissing]
>> 
>> PS:  I have learned quite a bit from this group in the past couple of
>> months.  John Miles, Gilbert, Mark Sims, Bob, etc, etc have been a lot of
>> help and have added a lot of enjoyment to my hobby.
>> 
>> [/end buttkissing]
>> 
>> ___
>> 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] Trimble Mini-T Timing Glitches

[jimlux]

On 11/30/17 1:31 PM, Leo Bodnar wrote:

Bob, this is quite an unorthodox description of how GPS works.
You probably want to rephrase that before it gets ripped to shreds.
Leo

From: Bob kb8tq 

GPS extracts time and location by locking on to various codes in the 
transmissions.

One of them happens to run at about a 1 KHz clock rate. A slip on that part of 
the
process gives you a (modulo) 1 ms clock jump. Certain types of interference may
“help” the receiver make these sorts of mistakes.


I thought it was fairly accurate - the primary thing from which you get 
your time reference is the C/A code epoch, which is a 1 millisecond sort 
of thing.  The Nav message is on top of that at 50 bps, but "GPS time" 
is reckoned in "weeks and milliseconds of week"  (e.g. that's what you 
get out of a variety of small Novatel single board receivers).


So a lot of receivers have a basic "cycle" that runs at the epoch rate.
To generate a 1pps, you take your current nav solution to figure out how 
far from the "epoch time for spacecraft #N" the "top of the second" is 
at, and then jam that into a counter of some sort that delays the epoch 
timing signal some number of clock ticks until the 1pps gets generated.


I suppose you could have some fancy system that takes the 1kHz ticks 
from ALL currently tracked satellites, and forms some sort of average to 
generate the 1pps signal.


But it's easier to take the "PN epoch sync" line, delay it by some 
number of processor clocks, and generate the 1pps.  Pick the strongest 
signal, since the epoch sync is probably "best".


It's also likely that the "epoch sync" is latched by the processor clock 
- hence hanging bridges, etc.


And all sorts of implementation idiosyncracies could confuse the "1pps 
logic" into putting the wrong delay count in.


BTW, it could well be a multimillisecond delay from "epoch sync" to 
"1pps"   For the purposes of illustration, let's say the range to the SV 
can vary by +/- 10,000km  - that's 30 milliseconds light time.


So I could be tracking SV1 at the horizon, calculate my delay, and then 
hiccup and now track SV2, directly overhead, but use the delay from SV1 
(until the next 1pps cycle comes around).


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[time-nuts] Rubidium freq standard - temperature

[Mark Sims]

43C seems reasonable for the baseplate temperature.

What is the model number for these?   Do you have a manual?   How are you 
setting the frequency?I just got in a Spectratime SRO100 and am adding 
support for it to Lady Heather.   I may also do the LPFRS which may be related 
to yours.
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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Attila Kinali]

On Thu, 30 Nov 2017 21:31:54 +
Leo Bodnar  wrote:

> From: Bob kb8tq 
> > GPS extracts time and location by locking on to various codes in the 
> > transmissions. 
> > One of them happens to run at about a 1 KHz clock rate. A slip on that part 
> > of the 
> > process gives you a (modulo) 1 ms clock jump. Certain types of interference 
> > may
> > “help” the receiver make these sorts of mistakes.

> Bob, this is quite an unorthodox description of how GPS works.
> You probably want to rephrase that before it gets ripped to shreds.

Actually, that's a pretty accurate, two sentence description.
It wouldnt be possible to build a GPS receiver using this, but
it's ok for the purpose.

On Thu, 30 Nov 2017 23:05:55 +
Leo Bodnar  wrote:

> I can't see how randomly selected 1ms of data can contain unambiguously 
> detectable start of C/A code.
> If NAV data bit phase flip occurred within this 1ms of data then correlation 
> search will most probably fail.
> Yes, the probability of this is only 5% (assuming equal number of 1s and 0s 
> in NAV message) but still not zero.
> Perhaps the quote should have added "carefully chosen 1ms of data"


The C/A code repeates every 1ms. The decoder cannot tell the repetitions
themselves appart at all. To solve this ambiguity, the decoder has to wait
for the flip caused by the tranmitted data, that happens exactly at those
1ms boundaries. As you noted, they happen only every 20ms (50baud data).
So, if you take these bit flips into account, there is now a 20ms ambiguity.
To resolve this, one has to wait for a start of frame (Preamble of the TLM
in GPS-speak), which then gives an 6s amibiguitiy, but as the data frame
contains the current time, the ambiguity can be completely resolved.

Now, depending on how the decoder is organized, it is totally possible,
that the decoder jumps by 1ms. Why doesn't this cause a loss of correltation?
Because most modern receivers use multiple C/A code-blocks for corrlation.
Correlation times of 10ms or 20ms are pretty normal, 100ms are not unheard of.
Thus, when using such long correlation times, slipping by 1ms will only cause
a slight degradation of C/N0 but it will still sufficiently high.
And also the data will decode correctly, because it's just a 5% (or -1.45dB) 
loss of signal assuming 20ms correlation time[1].

I've encountered modern receivers (aka not older than 5 years), that slip 
by 1ms under certain conditions.


> At the minimum, one would typically select 2ms of sampled data when they are 
> doing a correlation search and then
> they are guaranteed a full PRN sequence somewhere in there.

2ms is actually a pretty bad choice. If the bit flip happens within
those 2ms, then the correlation output, if perfectly matched, will 
be exactly zero (assuming no noise). You have to use either 1ms
correlation times, for aquisition, or a more sophisticated method.
Section 5.8 "signal acquisition" in Kaplan and Hegarty's book[2]
contains a few common techniques with good explanations.


Attila Kinali

[1] ok, it's actually more like 10%/1.91dB loss, because the
signal during that flipped 1ms is multiplied by -1 instead of +1, so it
causes twice the amount of signal los than uncorrelated signal

[2] "Understanding GPS - Principles and Applications", 2nd ed
by Kaplan and Hegarthy, 2006

-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] Rubidium freq standard - temperature

[paul swed]

Jerry
You have some EG RBs. Thats great news. Now I am not alone. I have 2 also
that work. I have found little details on them.
That said I believe they are intended to be mounted on a heat sink. One end
surely looks like that whats would be done.
I believe mine are LCR-10-T. Might have to double check that.
Regards
Paul
WB8TSL

On Thu, Nov 30, 2017 at 6:22 PM, Jerry Hancock  wrote:

> I was able to get all 5 of these EG Rubidium Frequency Standards running
> by replacing the caps as another member found.  They have a large heatsink
> on them, no fins, and are running at 43C.  Is that too hot?  Should I bolt
> them down to a larger heatsink?  They consume a little over 9w after they
> lock, about double that while warming up.
>
> The only other issue I see is that the 8bit frequency setting doesn’t
> allow me to set the frequency closer than 5E-11.  I don’t know if this is
> good for these units and RFS in general or not.
>
> Thanks.
>
> Jerry
>
> [/begin buttkissing]
>
> PS:  I have learned quite a bit from this group in the past couple of
> months.  John Miles, Gilbert, Mark Sims, Bob, etc, etc have been a lot of
> help and have added a lot of enjoyment to my hobby.
>
> [/end buttkissing]
>
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[time-nuts] Rubidium freq standard - temperature

[Jerry Hancock]

I was able to get all 5 of these EG Rubidium Frequency Standards running by 
replacing the caps as another member found.  They have a large heatsink on 
them, no fins, and are running at 43C.  Is that too hot?  Should I bolt them 
down to a larger heatsink?  They consume a little over 9w after they lock, 
about double that while warming up.

The only other issue I see is that the 8bit frequency setting doesn’t allow me 
to set the frequency closer than 5E-11.  I don’t know if this is good for these 
units and RFS in general or not.

Thanks.

Jerry

[/begin buttkissing]

PS:  I have learned quite a bit from this group in the past couple of months.  
John Miles, Gilbert, Mark Sims, Bob, etc, etc have been a lot of help and have 
added a lot of enjoyment to my hobby.  

[/end buttkissing]

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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Leo Bodnar]

Completely off-topic comment while on the subject:

I can't see how randomly selected 1ms of data can contain unambiguously 
detectable start of C/A code.
If NAV data bit phase flip occurred within this 1ms of data then correlation 
search will most probably fail.
Yes, the probability of this is only 5% (assuming equal number of 1s and 0s in 
NAV message) but still not zero.
Perhaps the quote should have added "carefully chosen 1ms of data"
At the minimum, one would typically select 2ms of sampled data when they are 
doing a correlation search and then they are guaranteed a full PRN sequence 
somewhere in there.

Leo

> From: Tom Van Baak Thu, 30 Nov 2017 14:43:02 -0800
> In order to find the beginning of a C/A code in the received signal only a
> very limited data record is needed such as 1 ms. If there is no Doppler effect
> on the received signal, then one millisecond of data contains all the 1,023 
> chips.
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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Tom Van Baak]

Leo,

About GPS and 1 ms...

1) Bob's version:

Bob's succinct description is fine. There is often a 1 ms loop in GPS receiver 
firmware (you can see this in the spec for some timing receivers). It is not 
impossible that off-by-1 errors would occur at this level.

2) Book version:

> Fundamentals of Global Positioning System Receivers: A Software Approach
>
> CHAPTER FIVE
> GPS C/A Code Signal Structure
>
> The C/A code is a bi-phase modulated signal with a chip rate of 1.023 MHz.
> Therefore, the null-to-null bandwidth of the main lobe of the spectrum is 
> 2.046
> MHz. Each chip is about 977.5 ns (1/1.023 MHz) long. The transmitting 
> bandwidth
> of the GPS satellite in the L1 frequency is approximately 20 MHz to
> accommodate the P code signal; therefore, the C/A code transmitted contains
> the main lobe and several sidelobes. The total code period contains 1,023 
> chips.
> With a chip rate of 1.023 MHz, 1,023 chips last 1 ms; therefore, the C/A code
> is 1 ms long. This code repeats itself every millisecond. The spectrum of a 
> C/A
> code is shown in Figure 5.2.
>
> In order to find the beginning of a C/A code in the received signal only a
> very limited data record is needed such as 1 ms. If there is no Doppler effect
> on the received signal, then one millisecond of data contains all the 1,023 
> chips.
> Different C/A codes are used for different satellites. The C/A code belongs to
> the family of Gold codes,(5) which will be discussed in the next section.
>
> Figure 5.3 shows the GPS data format. The first row shows a C/A code with
> 1,023 chips; the total length is 1 ms. The second row shows a navigation data
> bit that has a data rate of 50 Hz; thus, a data bit is 20 ms long and contains
> 20 C/A codes. Thirty data bits make a word that is 600 ms long as shown in
> the third row. Ten words make a subframe that is 6 seconds long as shown in
> row four. The fifth row shows a page that is 30 seconds long and contains 5
> subframes. Twenty-five pages make a complete data set that is 12.5 minutes
> long as shown in the sixth row. The 25 pages of data can be referred to as a
> superframe.

3) Tom's haiku version:

atomic clocks fly
coded signals drop from space
position is time

/tvb

- Original Message - 
From: "Bob kb8tq" 
To: "Discussion of precise time and frequency measurement" 
Sent: Thursday, November 30, 2017 2:14 PM
Subject: Re: [time-nuts] Trimble Mini-T Timing Glitches


Hi

I’d freely admit it is *very* much the “Cliff notes” version of what is 
happening.

Bob

> On Nov 30, 2017, at 4:31 PM, Leo Bodnar  wrote:
> 
> Bob, this is quite an unorthodox description of how GPS works.
> You probably want to rephrase that before it gets ripped to shreds.
> Leo
> 
> From: Bob kb8tq 
>> GPS extracts time and location by locking on to various codes in the 
>> transmissions. 
> One of them happens to run at about a 1 KHz clock rate. A slip on that part 
> of the 
> process gives you a (modulo) 1 ms clock jump. Certain types of interference 
> may
> “help” the receiver make these sorts of mistakes.
> 


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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Bob kb8tq]

Hi

I’d freely admit it is *very* much the “Cliff notes” version of what is 
happening.

Bob

> On Nov 30, 2017, at 4:31 PM, Leo Bodnar  wrote:
> 
> Bob, this is quite an unorthodox description of how GPS works.
> You probably want to rephrase that before it gets ripped to shreds.
> Leo
> 
> From: Bob kb8tq 
>> GPS extracts time and location by locking on to various codes in the 
>> transmissions. 
> One of them happens to run at about a 1 KHz clock rate. A slip on that part 
> of the 
> process gives you a (modulo) 1 ms clock jump. Certain types of interference 
> may
> “help” the receiver make these sorts of mistakes.
> 
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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Leo Bodnar]

Bob, this is quite an unorthodox description of how GPS works.
You probably want to rephrase that before it gets ripped to shreds.
Leo

From: Bob kb8tq 
>GPS extracts time and location by locking on to various codes in the 
>transmissions. 
One of them happens to run at about a 1 KHz clock rate. A slip on that part of 
the 
process gives you a (modulo) 1 ms clock jump. Certain types of interference may
“help” the receiver make these sorts of mistakes.

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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Bob kb8tq]

Hi

GPS extracts time and location by locking on to various codes in the 
transmissions. 
One of them happens to run at about a 1 KHz clock rate. A slip on that part of 
the 
process gives you a (modulo) 1 ms clock jump. Certain types of interference may
“help” the receiver make these sorts of mistakes. 

Bob

> On Nov 30, 2017, at 2:35 PM, Keith Loiselle  wrote:
> 
> Hello everyone,
> 
> I have heard reports of Trimble Mini-T timing glitches with offsets of 1ms
> lasting for about 30 seconds several times during the past week.  Some of
> the dates and times reported are at various locations include:
> 
> 23/11/2017, approx 11:00 UTC
> 
> 29/11/2017, approx 11:00 UTC
> 
> 30/11/2017, approx 12:00 UTC
> 
> We have not observed glitches with any of the equipment we have running,
> but we have not had any Trimble units running during the past week.  Has
> anyone else observed similar glitches recently with Trimble or other GPS
> equipment?
> 
> Thanks,
> 
> Keith
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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Tim Shoppa]

Historical: Ancient (as in Trimble SVeeSix - 20 or more years ago) Trimble
GPS units would have their PPS timing output offset by several milliseconds
when they lost a sufficient number of satellites to maintain a 4D solution.

The PPS offset would jump back and forth by a large step (I recall six
milliseconds) when tracking was borderline.

I do not expect anything modern to have problems like this.

Tim N3QE

On Thu, Nov 30, 2017 at 2:35 PM, Keith Loiselle 
wrote:

> Hello everyone,
>
> I have heard reports of Trimble Mini-T timing glitches with offsets of 1ms
> lasting for about 30 seconds several times during the past week.  Some of
> the dates and times reported are at various locations include:
>
> 23/11/2017, approx 11:00 UTC
>
> 29/11/2017, approx 11:00 UTC
>
> 30/11/2017, approx 12:00 UTC
>
> We have not observed glitches with any of the equipment we have running,
> but we have not had any Trimble units running during the past week.  Has
> anyone else observed similar glitches recently with Trimble or other GPS
> equipment?
>
> Thanks,
>
> Keith
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[time-nuts] Trimble Mini-T Timing Glitches

[Keith Loiselle]

Hello everyone,

I have heard reports of Trimble Mini-T timing glitches with offsets of 1ms
lasting for about 30 seconds several times during the past week.  Some of
the dates and times reported are at various locations include:

23/11/2017, approx 11:00 UTC

29/11/2017, approx 11:00 UTC

30/11/2017, approx 12:00 UTC

We have not observed glitches with any of the equipment we have running,
but we have not had any Trimble units running during the past week.  Has
anyone else observed similar glitches recently with Trimble or other GPS
equipment?

Thanks,

Keith
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Re: [time-nuts] Performance verification for time counters

[Poul-Henning Kamp]

In message <20171130181024.832c6adfd3cea0658ba43...@kinali.ch>, Attila Kinali w
rites:

>What puzzles me here is, the reason why someone would care
>about sub-1Hz frequencies in a telephone system? IIRC POTS
>did cut off somewhere areound 100-300Hz anyways.

They did not.

Most carrier frequency facilities had bottom frequencies in the 50kHz
area or higher.

Bob brought up the sub-Hz stuff, I pressume he knows what it is used for.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Performance verification for time counters

[Bob kb8tq]

Hi

They aren’t looking at voice signals, they are looking at the distribution 
of timing signals. The filters cut off well below voice frequencies. The
issue (as originally mentioned) is peaking in very long chains of repeaters.
Since the cutoff can be *very* low (just like with a GPSDO), the frequencies 
involved in a full amplitude and phase sweep are very low as well. If you want
very tight db accuracy, that pretty much implies that you have a good number
for “zero” frequency …… that puts you into silly season if somebody decides
it must be “tested in”. 

Bob

> On Nov 30, 2017, at 12:10 PM, Attila Kinali  wrote:
> 
> On Thu, 30 Nov 2017 09:39:59 -0500
> Bob kb8tq  wrote:
> 
>> That last decade ( 0.01 Hz period to 0.001 Hz)
> 
> What puzzles me here is, the reason why someone would care
> about sub-1Hz frequencies in a telephone system? IIRC POTS
> did cut off somewhere areound 100-300Hz anyways.
> 
>   Attila Kinali
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Performance verification for time counters

[Attila Kinali]

On Thu, 30 Nov 2017 09:39:59 -0500
Bob kb8tq  wrote:

>  That last decade ( 0.01 Hz period to 0.001 Hz)

What puzzles me here is, the reason why someone would care
about sub-1Hz frequencies in a telephone system? IIRC POTS
did cut off somewhere areound 100-300Hz anyways.

Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] ergodicity vs 1/f

[Bob kb8tq]

Hi

> On Nov 30, 2017, at 11:10 AM, Magnus Danielson  
> wrote:
> 
> 
> 
> On 11/30/2017 03:40 PM, Attila Kinali wrote:
>> On Thu, 30 Nov 2017 12:44:13 +0100
>> Mattia Rizzi  wrote:
>>> Let me emphasize your sentence:  "you will have a statistically significant
>>> number of samples of *one* realization of the random variable.".
>>> This sentence is the meaning of ergodic process [
>>> https://en.wikipedia.org/wiki/Ergodic_process]
>>> If it's ergodic, you can characterize the stochastic process using only one
>>> realization.
>>> If it's not, your measurement is worthless, because there's no guarantee
>>> that it contains all the statistical information.
>> You are mixing up ergodicity and reproducability.
>> Also, you are moving the goalpost.
>> We usually want to characterize a single clock or oscillator.
>> Not a production lot. As such the we only care about the statistical
>> properties of that single instance. If you want to verify that your
>> production lot has consistent performance metrics, then this is a
>> completely different goal and requires a different methodology. But
>> in the end it will boil down to measuring each clock/oscillator
>> individualy to make sure it fullfils the specs.
 A flat signal cannot be the realization of a random variable with
>>> a PSD ~ 1/f. At least not for a statisticially significant number
>>> of time-samples
>>> 
>>> Without ergodicity you cannot claim it. You have to suppose ergodicity.
>> If you demand ergodicity, you cannot have 1/f.
>> You can have only one or the other. Not both.
>> And if you choose ergodicity, you will not faithfully model a clock.
>>  
>>> If it's not stationary, it can change over time, therefore you are not
>>> authorized to use a SA. It's like measuring the transfer function of a
>>> time-varying filter (e.g. LTV system), the estimate doesn't converge.
>> Please take one of the SA's you have at CERN, measure an oscillator
>> for a long time and note down the center frequency with each measurement.
>> I promise you, you will be astonished.
> 
> After tons of measurements and attempts on theory a model was formed that was 
> sufficiently consistent with measurements.
> 
> The model that fits observation makes much of the traditional statistical 
> measures and definitions "tricky" to apply.
> 
> Flicker, that is PSD of 1/f, still is tricky to hunt down the real root and 
> model it, so we just use approximation in it's place because we need to have 
> something to work with.

I believe that was roughly the third thing the prof said when he introduced 1/F 
noise back when I was in school. It *might* have been
the fourth thing …. that was a long time ago ….

Bob

> Even without flicker, the white frequency noise messes with us.
> 
> This thread seems to lost contact with these aspects.
> 
> Cheers,
> Magnus
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Re: [time-nuts] ergodicity vs 1/f

[Magnus Danielson]

On 11/30/2017 03:40 PM, Attila Kinali wrote:

On Thu, 30 Nov 2017 12:44:13 +0100
Mattia Rizzi  wrote:


Let me emphasize your sentence:  "you will have a statistically significant
number of samples of *one* realization of the random variable.".
This sentence is the meaning of ergodic process [
https://en.wikipedia.org/wiki/Ergodic_process]
If it's ergodic, you can characterize the stochastic process using only one
realization.
If it's not, your measurement is worthless, because there's no guarantee
that it contains all the statistical information.


You are mixing up ergodicity and reproducability.

Also, you are moving the goalpost.
We usually want to characterize a single clock or oscillator.
Not a production lot. As such the we only care about the statistical
properties of that single instance. If you want to verify that your
production lot has consistent performance metrics, then this is a
completely different goal and requires a different methodology. But
in the end it will boil down to measuring each clock/oscillator
individualy to make sure it fullfils the specs.



A flat signal cannot be the realization of a random variable with

a PSD ~ 1/f. At least not for a statisticially significant number
of time-samples

Without ergodicity you cannot claim it. You have to suppose ergodicity.


If you demand ergodicity, you cannot have 1/f.
You can have only one or the other. Not both.
And if you choose ergodicity, you will not faithfully model a clock.
  

If it's not stationary, it can change over time, therefore you are not
authorized to use a SA. It's like measuring the transfer function of a
time-varying filter (e.g. LTV system), the estimate doesn't converge.


Please take one of the SA's you have at CERN, measure an oscillator
for a long time and note down the center frequency with each measurement.
I promise you, you will be astonished.


After tons of measurements and attempts on theory a model was formed 
that was sufficiently consistent with measurements.


The model that fits observation makes much of the traditional 
statistical measures and definitions "tricky" to apply.


Flicker, that is PSD of 1/f, still is tricky to hunt down the real root 
and model it, so we just use approximation in it's place because we need 
to have something to work with. Even without flicker, the white 
frequency noise messes with us.


This thread seems to lost contact with these aspects.

Cheers,
Magnus
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[time-nuts] ergodicity vs 1/f (was: Allan variance by sine-wave fitting)

[Attila Kinali]

On Thu, 30 Nov 2017 12:44:13 +0100
Mattia Rizzi  wrote:

> Let me emphasize your sentence:  "you will have a statistically significant
> number of samples of *one* realization of the random variable.".
> This sentence is the meaning of ergodic process [
> https://en.wikipedia.org/wiki/Ergodic_process]
> If it's ergodic, you can characterize the stochastic process using only one
> realization.
> If it's not, your measurement is worthless, because there's no guarantee
> that it contains all the statistical information.

You are mixing up ergodicity and reproducability.

Also, you are moving the goalpost. 
We usually want to characterize a single clock or oscillator.
Not a production lot. As such the we only care about the statistical
properties of that single instance. If you want to verify that your
production lot has consistent performance metrics, then this is a
completely different goal and requires a different methodology. But 
in the end it will boil down to measuring each clock/oscillator
individualy to make sure it fullfils the specs.


> >A flat signal cannot be the realization of a random variable with
> a PSD ~ 1/f. At least not for a statisticially significant number
> of time-samples
> 
> Without ergodicity you cannot claim it. You have to suppose ergodicity.

If you demand ergodicity, you cannot have 1/f.
You can have only one or the other. Not both.
And if you choose ergodicity, you will not faithfully model a clock.
 
> If it's not stationary, it can change over time, therefore you are not
> authorized to use a SA. It's like measuring the transfer function of a
> time-varying filter (e.g. LTV system), the estimate doesn't converge.

Please take one of the SA's you have at CERN, measure an oscillator
for a long time and note down the center frequency with each measurement.
I promise you, you will be astonished.


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Performance verification for time counters

[Bob kb8tq]

Hi

Sweep the transfer function from 100 Hz down to 0.001 Hz at 50 points per 
decade.
Spend enough time at each point to get to 0.001 db sort of accuracy. The first 
decade
goes pretty fast. That last decade ( 0.01 Hz period to 0.001 Hz) …. not so 
much. The
request always has both the silly frequency and the nonsense db fraction in it 
….

Bob

> On Nov 30, 2017, at 3:29 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message <42a2f881-1631-402c-8ed6-2c863f6fe...@n1k.org>, Bob kb8tq writes:
> 
 Needless to say *demonstrating* this 0.001 db sort of gain flatness on a 
 repeater
 out to crazy low frequencies is a bit involved. It *is* a great gig if you 
 happen to be
 a consultant …
>>> 
>>> demonstrating 0.001 dB (or would that really be 0.1 mB or 100 microBels) 
>>> precision in *any* application is a bit involved.  That's 0.03%
>>> 
>> 
>> Yup, now do it at some silly low frequency ( 0.(some number of zeros)1 Hz …. 
>> great way to waste a lot of time. 
> 
> Sorry, I don't see the challenge:  HP3458A in sampling mode, careful cabling, 
> done.
> 
> At RF frequencies where you have to think about impedance however...
> 
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Performance verification for time counters

[Leo Bodnar]

Thank you for great suggestions, I will try to set something up next week 
involving detuned clock or sinewave source.

Leo
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Re: [time-nuts] Allan variance by sine-wave fitting

[Mattia Rizzi]

Hi,

@All
>True that the models depend on the noise statistics to be iid, that is
ergodic. That's the first assumption, and, while making the math tractable,
is the worst assumption.

I am not talking about intractable math. I'm talking about experimental
hypothesis vs theory.
I said that if you follow strictly the theory, you cannot claim anything on
any stuff you're measuring that may have a flicker process.
Therefore, any experimentalist suppose ergodicity in his measurements.

@Attila
>I do not see how ergocidity has anything to do with a spectrum analyzer.
You are measuring one single instance. Not multiple [...] And about
statistical significance: yes, you will have zero statistical significance
about the behaviour of the population of random variables, but you will
have a statistically significant number of samples of *one* realization of
the random variable. And that's what you work with.

Let me emphasize your sentence:  "you will have a statistically significant
number of samples of *one* realization of the random variable.".
This sentence is the meaning of ergodic process [
https://en.wikipedia.org/wiki/Ergodic_process]
If it's ergodic, you can characterize the stochastic process using only one
realization.
If it's not, your measurement is worthless, because there's no guarantee
that it contains all the statistical information.


>A flat signal cannot be the realization of a random variable with
a PSD ~ 1/f. At least not for a statisticially significant number
of time-samples

Without ergodicity you cannot claim it. You have to suppose ergodicity.

>And no, you do not need stationarity either. The spectrum analyzer has
a lower cut of frequency, which is given by its update rate and the
inner workings of the SA.

You need stationarity. Your SA takes several snapshots of the realization,
with an assumption: the characteristics of the stochastic process are not
changing over time. If the stochastic process is stationary, the
autocorrelation function doesn't depend over time. So you are authorized to
take several snapshots, compensate for the obseveration time (low cut-off
frequency) (*), and be sure that the estimated PSD will converge to
something meaningful.
If it's not stationary, it can change over time, therefore you are not
authorized to use a SA. It's like measuring the transfer function of a
time-varying filter (e.g. LTV system), the estimate doesn't converge.

cheers,
Mattia


(*) You can compensate the measured PSD to mimic the stochastic process
PSD, because the SA is a LTI system.

2017-11-28 20:23 GMT+01:00 djl :

> True that the models depend on the noise statistics to be iid, that is
> ergodic. That's the first assumption, and, while making the math tractable,
> is the worst assumption.
> Don
>
>
> On 2017-11-28 01:52, Mattia Rizzi wrote:
>
>> Hi
>>
>> This is true. But then the Fourier transformation integrates time from
>>>
>> minus infinity to plus infinity. Which isn't exactly realistic either.
>>
>> That's the theory. I am not arguing that it's realistic.
>>
>> Ergodicity breaks because the noise process is not stationary.
>>>
>>
>> I know but see the following.
>>
>> Well, any measurement is an estimate.
>>>
>>
>> It's not so simple. If you don't assume ergodicity, your spectrum analyzer
>> does not work, because:
>> 1) The spectrum analyzer takes several snapshots of your realization to
>> estimate the PSD. If it's not stationary, the estimate does not converge.
>> 2) It's just a single realization, therefore also a flat signal can be a
>> realization of 1/f flicker noise. Your measurement has *zero* statistical
>> significance.
>>
>>
>>
>> 2017-11-27 23:50 GMT+01:00 Attila Kinali :
>>
>> Hoi Mattia,
>>>
>>> On Mon, 27 Nov 2017 23:04:56 +0100
>>> Mattia Rizzi  wrote:
>>>
>>> > >To make the point a bit more clear. The above means that noise with
>>> > > a PSD of the form 1/f^a for a>=1 (ie flicker phase, white frequency
>>> > > and flicker frequency noise), the noise (aka random variable) is:
>>> > > 1) Not independently distributed
>>> > > 2) Not stationary
>>> > > 3) Not ergodic
>>> >
>>> > I think you got too much in theory. If you follow striclty the
>>> statistics
>>> > theory, you get nowhere.
>>> > You can't even talk about 1/f PSD, because Fourier doesn't converge
>>> over
>>> > infinite power signals.
>>>
>>> This is true. But then the Fourier transformation integrates time from
>>> minus infinity to plus infinity. Which isn't exactly realistic either.
>>> The power in 1/f noise is actually limited by the age of the universe.
>>> And quite strictly so. The power you have in 1/f is the same for every
>>> decade in frequency (or time) you go. The age of the universe is about
>>> 1e10 years, that's roughly 3e17 seconds, ie 17 decades of possible noise.
>>> If we assume something like a 1k carbon resistor you get something around
>>> of 1e-17W/decade of noise power (guestimate, not an exact calculation).
>>> That 

Re: [time-nuts] Performance verification for time counters

[Poul-Henning Kamp]

In message <42a2f881-1631-402c-8ed6-2c863f6fe...@n1k.org>, Bob kb8tq writes:

>>> Needless to say *demonstrating* this 0.001 db sort of gain flatness on a 
>>> repeater
>>> out to crazy low frequencies is a bit involved. It *is* a great gig if you 
>>> happen to be
>>> a consultant …
>>
>> demonstrating 0.001 dB (or would that really be 0.1 mB or 100 microBels) 
>> precision in *any* application is a bit involved.  That's 0.03%
>> 
>
>Yup, now do it at some silly low frequency ( 0.(some number of zeros)1 Hz …. 
>great way to waste a lot of time. 

Sorry, I don't see the challenge:  HP3458A in sampling mode, careful cabling, 
done.

At RF frequencies where you have to think about impedance however...


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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