[time-nuts] quartz / liquid nitrogen

[Mark Sims]

And you want your semiconductors to be in ceramic/lided packages with the bond 
wires flapping in free air.   Bond wires embedded in epoxy like to break...  
don't ask how I found this out  ;-)   ... it brings back bad memories... and 
makes bad memories...  Quantum chips have very elaborate/specialized bonding to 
survive liquid helium... even with that, thermal cycling still breaks them.
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[time-nuts] TV Signals as a frequency reference

[Mark Sims]

Here's a local guy's take on monitoring time and DST errors on the stations in 
the Dallas area:
http://home.earthlink.net/~schultdw/atsc/
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[time-nuts] Harrison's birthday

[jimlux]

Google reminds us that 3 April is Harrison's birthday..

https://en.wikipedia.org/wiki/John_Harrison

Interesting he (depending on your calendar) was born and died on the 
same day.  And, interesting he died in 1776, which is of some 
significance in the US.

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Re: [time-nuts] TV Signals as a frequency reference

[Trent Piepho]

I wrote a program that would scan the PSIP data from my local stations
and the STT was always quite poor.  Usually several stations had the
GPS-UTC offset that was stale, even a year after a leap second.  It
would be trivial to make an automatic correct STT generator some
online data (NTP, etc.), why this was not part of the software that
generated the PSIP data is a mystery to me.

DST was a mess.  I think this bit from A/65 was confusing:

When the transition into daylight saving time is between one
day less than one month away and the actual transition the
DS_day_of_month field takes the value day_in, and the DS_hour field
takes the value hour_in. The DS_status bit is 0 indicating it is not
yet daylight saving time.

What exactly does "less than one month away" mean?  Does it mean less
than 31*24 hours away?  Does it mean in the current calendar month?

What happens is you get a STT that says "DST begins on the 11th at
2:00 AM".  They couldn't figure out how to pack the month in 16 bits
so you just get "the 11th", no month.  It's now Feb 12th.  Has DST
started?  Some devices would decide the answer is yes and others no.



On Mon, Apr 2, 2018 at 10:08 AM, Mark Sims  wrote:
> I read that there is a requirement that the time data in the PSIP data stream 
> has to be within one second.
>
> I have an over-the-air DVR that would mess up the time and recordings because 
> it was originally not filtering the times the stations broadcast.   They 
> finally modified the DVR firmware to do something like a median filter to 
> throw out the outliers.   A local TV guru beat up on all the local stations 
> with a copy of the FCC rules to get the stations to broadcast the correct 
> time.   And don't me started on the ways the stations still mess up the 
> daylight savings time transitions.  Many are a month, week, or day off.
>
> ---
>
>> There is no requirement for us to inject time of any prescribed accuracy
> into the digital stream.
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Re: [time-nuts] quartz / liquid nitrogen

[jimlux]

On 4/2/18 1:39 PM, Hal Murray wrote:

If not Nitrogen, how about dry ice (-109F -78C)?


Dry ice is relatively easy to get.  It wouldn't be hard to try a quick
experiment.





CTE mismatch in packages will be a significant problem - you might find 
that your ICs don't work because bond wires have been ripped off the 
die. Parts might have popped off the board too.


But if you have one, and it's sacrificable, give it a try - a cooler 
with some dry ice, and put the circuit above the dry ice, and it will 
cool slowly

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[time-nuts] Fwd: quartz / liquid nitrogen

[Alexander Pummer]

at low temperatures bipolar devices will have reduced gain

73

KJ6UHN

Alex



 Forwarded Message 
Subject:[time-nuts] quartz / liquid nitrogen
Date:   Mon, 2 Apr 2018 12:46:26 -0700
From:   Tom Van Baak 
Reply-To: 	Tom Van Baak , Discussion of precise time 
and frequency measurement 

Organization:   LeapSecond.com
To: 	Discussion of precise time and frequency measurement 





Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: -196 
C (-321F, 77K)? It's probably impractical commercially, but maybe something of 
value to a time nut. Would that dramatically lower temperature improve phase noise 
& short-term performance? Is there a crystal cut that could be optimized for 77 
K instead of ~25 C (room) or 60 C (oven)?

If not Nitrogen, how about dry ice (-109F -78C)?

/tvb

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---
This email has been checked for viruses by AVG.
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Re: [time-nuts] quartz / liquid nitrogen

[Bob kb8tq]

Hi



> On Apr 2, 2018, at 5:38 PM, Attila Kinali  wrote:
> 
> On Mon, 2 Apr 2018 12:46:26 -0700
> "Tom Van Baak"  wrote:
> 
>> Has anyone tried running a quartz oscillator at liquid nitrogen 
>> temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, 
>> but maybe something of value to a time nut. Would that dramatically lower 
>> temperature improve phase noise & short-term performance? Is there a crystal 
>> cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)?
>> 
>> If not Nitrogen, how about dry ice (-109F -78C)?
> 
> Yes, it has been done. Down to liquid helium tempratures even.
> The main benefit is that the Q of the crystal increses with
> decreasing temperatures, but the effect is not as large as with
> dielectric resonators (aka whispering galery mode CSO). 
> 
> Of course thermal noise decreases as well, but usually quartz
> oscillators are limited by their amplifiers and the 50 Ohm system
> for termal noise. I do not remember reading anything about flicker
> noise, but my guess would be that it decreases as well.

The gotcha there is that the 1/F noise of the resonator is already below 
the oscillator “result” at room temperature. Reducing it further is great, 
but it doesn’t translate directly to an improved signal source. 

Unless you have a “flat” crystal temperature wise *and* good temperature
controll (like micro degree level) improving ADEV …. not so much. 

Bob


> 
> I am sure I have some paper on this somewhere in my collection,
> if you want I can dig it out.
> 
>   Attila Kinali
> 
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
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Re: [time-nuts] quartz / liquid nitrogen

[Attila Kinali]

On Mon, 2 Apr 2018 12:46:26 -0700
"Tom Van Baak"  wrote:

> Has anyone tried running a quartz oscillator at liquid nitrogen 
> temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, 
> but maybe something of value to a time nut. Would that dramatically lower 
> temperature improve phase noise & short-term performance? Is there a crystal 
> cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)?
> 
> If not Nitrogen, how about dry ice (-109F -78C)?

Yes, it has been done. Down to liquid helium tempratures even.
The main benefit is that the Q of the crystal increses with
decreasing temperatures, but the effect is not as large as with
dielectric resonators (aka whispering galery mode CSO). 

Of course thermal noise decreases as well, but usually quartz
oscillators are limited by their amplifiers and the 50 Ohm system
for termal noise. I do not remember reading anything about flicker
noise, but my guess would be that it decreases as well.

I am sure I have some paper on this somewhere in my collection,
if you want I can dig it out.

Attila Kinali


-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] quartz / liquid nitrogen

[Bob kb8tq]

Hi

If you dig back in the FCS archives, you will find papers on “cold” OCXO’s. You 
also 
will find papers on cryo cooled quartz. The bottom line appears to be that if 
you are
going to all the trouble of cooling things, sapphire (or other exotic 
materials) are a 
better bet. 

Quick simple answer: not enough improvement in ADEV, aging, or phase noise to 
make it wroth it. As PHK mentioned, coming up with a “ideal” cut for your 
arbitrary
temperature  cryo setup is non-trivially difficult ( = plan on spending a few 
million 
dollars and a lot of years).

Bob

> On Apr 2, 2018, at 3:46 PM, Tom Van Baak  wrote:
> 
> Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: 
> -196 C (-321F, 77K)? It's probably impractical commercially, but maybe 
> something of value to a time nut. Would that dramatically lower temperature 
> improve phase noise & short-term performance? Is there a crystal cut that 
> could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)?
> 
> If not Nitrogen, how about dry ice (-109F -78C)?
> 
> /tvb
> 
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Re: [time-nuts] quartz / liquid nitrogen

[djl]

Tom: I sense a nice experiment!  Dry ice temps can be attained with 
modest Dewars and thermoelectric fridge devices. PID controller and 
bob's your uncle.  Type K thermocouple modules on epay.   With that 
apparat, a nice set of adev vs temperature possible?  Dry ice/acetone or 
ethyl alcohol (everclear) slurry is often used as a calibration point 
BTW. Liquid N2 may be too cold, or is it He I'm thinking of???

Don
On 2018-04-02 13:46, Tom Van Baak wrote:

Has anyone tried running a quartz oscillator at liquid nitrogen
temperatures: -196 C (-321F, 77K)? It's probably impractical
commercially, but maybe something of value to a time nut. Would that
dramatically lower temperature improve phase noise & short-term
performance? Is there a crystal cut that could be optimized for 77 K
instead of ~25 C (room) or 60 C (oven)?

If not Nitrogen, how about dry ice (-109F -78C)?

/tvb

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--
Dr. Don Latham
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

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Re: [time-nuts] quartz / liquid nitrogen

[Brooke Clarke]

Hi Tom:

Put the dry ice in acetone to the lowest temp.

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

 Original Message 

Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: -196 
C (-321F, 77K)? It's probably impractical commercially, but maybe something of 
value to a time nut. Would that dramatically lower temperature improve phase noise 
& short-term performance? Is there a crystal cut that could be optimized for 77 
K instead of ~25 C (room) or 60 C (oven)?

If not Nitrogen, how about dry ice (-109F -78C)?

/tvb

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Re: [time-nuts] quartz / liquid nitrogen

[Tisha Hayes]

You also run in to mechanical vibration issues from the cooling system. At
the temperatures involved you are looking at something like a Stirling
cycle cooler.

Here is a good article;

https://arxiv.org/pdf/1309.5445.pdf

Maintaining a very stable temperature probably has a much greater impact.

Tisha Hayes, AA4HA

*Ms. Tisha Hayes*


On Mon, Apr 2, 2018 at 2:58 PM, Poul-Henning Kamp 
wrote:

> 
> In message <299B45118C9248498D7B4F3AFE72231E@pc52>, "Tom Van Baak" writes:
>
> >Has anyone tried running a quartz oscillator at liquid nitrogen
> >temperatures: -196 C (-321F, 77K)? It's probably impractical
> >commercially, but maybe something of value to a time nut.
>
> Whispering gallery sapphire resonators at cryogenic temperatures
> is a thing for phase-noise, but those are dielectric (microwave)
> resonators, not piezoelectric resonators.
>
> > Would that dramatically lower temperature improve phase noise &
> > short-term performance?
>
> Yes it will reduce your thermal noise as a source of PN, and
> dramatically so.
>
> But I doubt short and long term performance will improve.
>
> Even if you can find a zero-turnover cut at a convenient temperature,
> I don't think anybody know how to produce mK temperature *stability*
> at cryogenic temperatures ?
>
> --
> 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] quartz / liquid nitrogen

[Hal Murray]

> If not Nitrogen, how about dry ice (-109F -78C)?

Dry ice is relatively easy to get.  It wouldn't be hard to try a quick 
experiment.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] quartz / liquid nitrogen

[Dana Whitlow]

Is the thermal noise generated in the loss in a quartz resonator a
significant part
of the overall phase noise picture?  I would have not thought so.  I'd
think that a
greater benefit ought to be derived from chilling the other parts in the
oscillator,
such as the active devices.  Unless, of course, chilling the quartz
actually improves
the Q significantly, which I don't know about.

If cooling (whatever) by just a modest amount helps much, then one could
consider using Peltier cooling.  It doesn't really get things very cold,
but is a
lot more convenient than either dry ice or LN2.  But then you don't get the
fun
that you do when playing with LN2, either.

Dana


On Mon, Apr 2, 2018 at 2:46 PM, Tom Van Baak  wrote:

> Has anyone tried running a quartz oscillator at liquid nitrogen
> temperatures: -196 C (-321F, 77K)? It's probably impractical commercially,
> but maybe something of value to a time nut. Would that dramatically lower
> temperature improve phase noise & short-term performance? Is there a
> crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60
> C (oven)?
>
> If not Nitrogen, how about dry ice (-109F -78C)?
>
> /tvb
>
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Re: [time-nuts] quartz / liquid nitrogen

[Poul-Henning Kamp]

In message <299B45118C9248498D7B4F3AFE72231E@pc52>, "Tom Van Baak" writes:

>Has anyone tried running a quartz oscillator at liquid nitrogen
>temperatures: -196 C (-321F, 77K)? It's probably impractical
>commercially, but maybe something of value to a time nut.

Whispering gallery sapphire resonators at cryogenic temperatures
is a thing for phase-noise, but those are dielectric (microwave)
resonators, not piezoelectric resonators.

> Would that dramatically lower temperature improve phase noise &
> short-term performance?

Yes it will reduce your thermal noise as a source of PN, and
dramatically so.

But I doubt short and long term performance will improve.

Even if you can find a zero-turnover cut at a convenient temperature,
I don't think anybody know how to produce mK temperature *stability*
at cryogenic temperatures ?

-- 
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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[time-nuts] quartz / liquid nitrogen

[Tom Van Baak]

Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: 
-196 C (-321F, 77K)? It's probably impractical commercially, but maybe 
something of value to a time nut. Would that dramatically lower temperature 
improve phase noise & short-term performance? Is there a crystal cut that could 
be optimized for 77 K instead of ~25 C (room) or 60 C (oven)?

If not Nitrogen, how about dry ice (-109F -78C)?

/tvb

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Re: [time-nuts] timing an ITR master clock

[Tom Van Baak]

Jerry,

Most people I know who time mechanical clocks use Bryan Mumford's Microset 
timer:

  https://www.bmumford.com/microset.html

  https://www.bmumford.com/mset/model3.html

Bryan has a wide variety of sensors: optical, acoustic, magnetic, laser, etc.

Of course it is possible to home-brew a solution. Many of us have done that. 
But it's not quite as easy as it sounds to get a system that gives you reliable 
data.

Several people use PC's as the timer, but be aware that pendulum clocks can 
easily achieve ppm levels of stability in which case the data you get might 
actually be your PC being timed by a pendulum, not a pendulum being timed by a 
PC.

You might also get good advice from one of the watch & clock forums on the 
'net. We tend to stay away from generic mechanical clock topics here on 
time-nuts.

/tvb

- Original Message - 
From: "Jerry Hancock" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, April 02, 2018 8:42 AM
Subject: [time-nuts] timing an ITR master clock


>I have a new to me International Time Recorder (pre-IBM) master clock.  I has 
>second, minute and hour closures and was thinking of using the second closure 
>to check the beat and time.  If others have done this kind of thing, let me 
>know.  I have a mix of timing equipment, of course, and have to be careful 
>with DC always, so I was thinking of just using an oscillator looped through 
>the second switch to get a rough idea of the timing.
> 
> Thoughts?  Beautiful clock, a friend of mine is the current expert having 
> over 300 such clocks and affiliated secondary clocks, etc.
> 
> Regards,
> 
> Jerry
> 
> 
> Jerry Hancock
> je...@hanler.com
> (415) 215-3779
> 
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[time-nuts] TV Signals as a frequency reference

[Mark Sims]

I read that there is a requirement that the time data in the PSIP data stream 
has to be within one second.  

I have an over-the-air DVR that would mess up the time and recordings because 
it was originally not filtering the times the stations broadcast.   They 
finally modified the DVR firmware to do something like a median filter to throw 
out the outliers.   A local TV guru beat up on all the local stations with a 
copy of the FCC rules to get the stations to broadcast the correct time.   And 
don't me started on the ways the stations still mess up the daylight savings 
time transitions.  Many are a month, week, or day off.

---

> There is no requirement for us to inject time of any prescribed accuracy 
into the digital stream.
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[time-nuts] timing an ITR master clock

[Jerry Hancock]

I have a new to me International Time Recorder (pre-IBM) master clock.  I has 
second, minute and hour closures and was thinking of using the second closure 
to check the beat and time.  If others have done this kind of thing, let me 
know.  I have a mix of timing equipment, of course, and have to be careful with 
DC always, so I was thinking of just using an oscillator looped through the 
second switch to get a rough idea of the timing.

Thoughts?  Beautiful clock, a friend of mine is the current expert having over 
300 such clocks and affiliated secondary clocks, etc.

Regards,

Jerry


Jerry Hancock
je...@hanler.com
(415) 215-3779

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[time-nuts] New GNSS chipsets

[Mark Sims]

I was measuring the jitter and adevs of the PPS signal from a GT-8736.   GPS 
only seems to be slightly better (1-3 ns more span) than GPS+GLONASS.  GLONASS 
only seems have around 50% more jitter than GPS only.  Glonaas only adevs are 3 
times as large as GPS only (at tau=1 seconds).  
 
-

> It is indeed a benefit to use the different constellations.
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Re: [time-nuts] GPS ANTENNA

[Bob kb8tq]

Hi

The problem with “to much gain” is that it is very hard to tell when you have 
to much gain. 
The system quite happily chugs along reporting fine S/N ratios. Cut the gain by 
20 db and
you get the same C/N ratios. The reason is pretty simple - the noise figure is 
set by the 
front end of the preamp. As long as you have “enough” gain it will dominate. Is 
“enough”
10 db or 100 db? Either way it’s enough to make that equation work.

The issue comes in mainly because these modules have a limited AGC range (or 
dynamic
range). For whatever reason, the AGC situation is not reported upstream. If the 
module has
run out of AGC and is about to loose it …. you simply have no way to tell. 

It’s not just TimeNuts that have trouble with this stuff. Very large / smart / 
big budget / outfits
run into this stuff as well. The same issues of poorly documented system 
requirements / 
non-standard system requirements are a major hassle for them. I’ve seen them 
spend 
major effort because of this stuff. 

So how to work it out? 

Stuff a (dc blocked) variable attenuator in the line. Pick a sat that is 
reporting something like
35 db S/N. Flip between two attenuator settings every 30 seconds or so. Note 
any change. 
Do it multiple times with multiple sats. Then move on to your next settings 
pair. I’d start big,
maybe a 10 db step and go smaller if you can stand the boredom. 

As long as 35 db stays roughly 35 db, you have “enough” gain. Since sat’s move 
and that 
impacts S/N, there is no exact 0.05 db sort of number. Even looking at numbers 
over a day
can be tricky. Things are never quite the same today as they were yesterday. 

It does seem strange that you want the minimum gain. It’s not so strange if you 
dig into things
like land mobile radio design. Your best overload performance is always going 
to be the 
design with barely enough gain in the front end. 

Lots of fun. 

Bob

> On Apr 2, 2018, at 6:07 AM, ew via time-nuts  wrote:
> 
> Question
> Using L/H  what is too much signal 
> Bert Kehren
>  
> In a message dated 4/1/2018 10:54:23 PM Eastern Standard Time, 
> david.partri...@perdrix.co.uk writes:
> 
>  
> just use a bias tee to feed in the antenna volts :)
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio 
> Boriani
> Sent: 01 April 2018 23:29
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS ANTENNA
> 
> An unusual attenuator with a DC pass.
> 
> On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge 
>  wrote:
>> Or use a choke ring survey antenna and an attenuator :)
>> 
>> Dave
>> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
>> kb8tq
>> Sent: 01 April 2018 14:43
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] GPS ANTENNA
>> 
>> Hi
>> 
>> Indeed, it is *very* easy to put to much gain in front of a timing GNSS 
>> receiver. These beasts are trying to dig out a signal that you can’t even 
>> see with a spectrum analyzer.
>> It’s way to far below the noise floor to detect that way. They optimize 
>> things pretty tightly to get that done (and to hit a price target ….). Put 
>> to much gain in front of them and they get unhappy.
>> 
>> Making this even more crazy, the survey industry standard antenna *does* 
>> have a lot of gain. Survey receivers need way more gain in front of them 
>> than timing receivers. Put a survey antenna directly on a timing device and 
>> trouble will likely be the outcome. Equally, a survey instrument probably 
>> will not be happy with a timing receiver.
>> 
>> Why all this nonsense? As far as I can tell, it goes back to how the very 
>> early L1 / L2 survey boxes were designed back in the 1980’s and early 
>> 1990’s. They made a basic decision to put a lot of gain at the antenna. 
>> Motorola came along with their GPS modules later on. They made a *very* 
>> different decision about how to distribute the gain. There are very good 
>> arguments on both sides for why they did it this way.
>> The bottom line is still - you need to match things up …
>> 
>> Bob
>> 
>>> On Apr 1, 2018, at 2:36 AM, cfo  wrote:
>>> 
>>> On Sat, 31 Mar 2018 10:58:19 -0500,
>>> donandarline-Re5JQEeQqe8AvxtiuMwx3w
>>> wrote:
>>> 
 I found a supplier for high quality GPS antennas at a very 
 reasonable price. PCTEL GPSL1-TMG-SPI-40NCB.
>>> 
>>> *** SNIP ***
>>> 
>>> I had one of those on 25m cable, and it worked fine on a Tbolt , 
>>> until i got an active antenna splitter that also had some gain.
>>> Then i had to replace it w. a 26dB version of same type, else the 
>>> "Jackson Lite" was loosing sync.
>>> 
>>> What i mean here, is that you can get too much gain too.
>>> 
>>> Btw: Good price.
>>> 
>>> CFO
>>> Denmark
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com To 

Re: [time-nuts] GPS ANTENNA

[Bob kb8tq]

Hi

As you rummage around your junk box, do be a bit careful Most of what I have 
here are
tee’s that include DC blocks. There are blocks that don’t do that. Trying to 
run your bias
supply into 50 or 25 ohms is not a real good idea.

Bob

> On Apr 1, 2018, at 9:43 PM, David C. Partridge 
>  wrote:
> 
> just use a bias tee to feed in the antenna volts :)
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio 
> Boriani
> Sent: 01 April 2018 23:29
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS ANTENNA
> 
> An unusual attenuator with a DC pass.
> 
> On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge 
>  wrote:
>> Or use a choke ring survey antenna and an attenuator :)
>> 
>> Dave
>> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
>> kb8tq
>> Sent: 01 April 2018 14:43
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] GPS ANTENNA
>> 
>> Hi
>> 
>> Indeed, it is *very* easy to put to much gain in front of a timing GNSS 
>> receiver. These beasts are trying to dig out a signal that you can’t even 
>> see with a spectrum analyzer.
>> It’s way to far below the noise floor to detect that way. They optimize 
>> things pretty tightly to get that done (and to hit a price target ….). Put 
>> to much gain in front of them and they get unhappy.
>> 
>> Making this even more crazy, the survey industry standard antenna *does* 
>> have a lot of gain. Survey receivers need way more gain in front of them 
>> than timing receivers. Put a survey antenna directly on a timing device and 
>> trouble will likely be the outcome. Equally, a survey instrument probably 
>> will not be happy with a timing receiver.
>> 
>> Why all this nonsense? As far as I can tell, it goes back to how the very 
>> early L1 / L2 survey boxes were designed back in the 1980’s and early 
>> 1990’s. They made a basic decision to put a lot of gain at the antenna. 
>> Motorola came along with their GPS modules later on. They made a *very* 
>> different decision about how to distribute the gain. There are very good 
>> arguments on both sides for why they did it this way.
>> The bottom line is still - you need to match things up …
>> 
>> Bob
>> 
>>> On Apr 1, 2018, at 2:36 AM, cfo  wrote:
>>> 
>>> On Sat, 31 Mar 2018 10:58:19 -0500,
>>> donandarline-Re5JQEeQqe8AvxtiuMwx3w
>>> wrote:
>>> 
 I found a supplier for high quality GPS antennas at a very 
 reasonable price. PCTEL GPSL1-TMG-SPI-40NCB.
>>> 
>>> *** SNIP ***
>>> 
>>> I had one of those on 25m cable, and it worked fine on a Tbolt , 
>>> until i got an active antenna splitter that also had some gain.
>>> Then i had to replace it w. a 26dB version of same type, else the 
>>> "Jackson Lite" was loosing sync.
>>> 
>>> What i mean here, is that you can get too much gain too.
>>> 
>>> Btw: Good price.
>>> 
>>> CFO
>>> Denmark
>>> 
>>> ___
>>> 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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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] New GNSS chipsets

[Bob kb8tq]

Hi



> On Apr 1, 2018, at 9:47 PM, Hal Murray  wrote:
> 
> 
> mag...@rubidium.dyndns.org said:
>> I have advocated for receivers able to handle multiple frequencies and
>> multiple GNSS for some time, sneaking it into documents, so there should be
>> some preparations for this now.
> 
> How well do various GNSS track UTC and/or eachother?

These days Glonass puts out an offset number that should be good to the single 
digit nanoseconds (unless it’s broke). The Europeans have set up to effectively 
stay
“as close as you can get” to sync. Right now those are the only three that are 
likely 
candidates for time sources. 

> 
> 
>> The benefit is naturally redundancy, but also higher precision. 
> 
> I've been assuming the cheap GPS jammers will kill the others too.

Maybe not. Glonass is not on quite the same frequencies. The signal formats of
each system are very different. A jammer that nukes one may not have any 
impact on the rest. Indeed a megawatt level broadband DC to light jammer 
would take out a lot of things. It’s also a pretty easy item to track down. 

Straight broadband jamming *should* simply shut a receiver down. That’s why 
GPSDO’s go into holdover (and why you have GPSDO’s). Are all receivers ever 
made perfect in the face of any and all crud … maybe not. 

The bigger issue is a “spoof” signal that deliberately tricks the receiver into 
thinking
it is locked to legitimate satellites. There are ways to do that. Receivers are 
not
going to reject that solution and away you go. Doing a working spoof for 
multiple 
systems …. much harder than a single system. 

Bob


>  Are there 
> any signals far enough away from L1 that they might get through?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] New GNSS chipsets

[Bob kb8tq]

Hi

A….. but ….. 

The uBlox parts are available with the existing chip sets pretty easily today.
That has not always been the case with uBlox. Back when the chips were
new / unique / hard to support it was significantly more difficult to get 
anything
out of them (at least at a rational price). 

Broadcom …. yikes … I’ve sat in around in meetings where giant telecom 
companies can’t get adequate information on chips they are using from 
those guys. Even simple stuff like “what does this register do”. Three years
later back comes “the XXX register must be set this way for the chip not to
lock up intermittently” …. gee … maybe it wasn’t Bob’s fault :)

It *is* a big bet so I can’t say any of this with certainty. It’s simply my 
guess 
that on something this complex, we are back to the way things worked a 
decade or two ago. 

Bob

> On Apr 1, 2018, at 8:06 PM, Joseph Gray  wrote:
> 
> Bob,
> 
> If it was a glass of good bourbon, I'd take you up on that offer :-)
> 
> The Broadcom chipsets are touted as being specifically for phones. Whether
> we'll be able to buy stand alone modules, I don't know. The uBlox chipsets
> have in that past been widely available at rational prices. Hopefully the
> new "9" series will be, also. As for the ST Micro, I haven't a clue, but
> considering how their microcontrollers are so widely available from China,
> who knows what will happen.
> 
> Joe Gray
> W5JG
> 
> 
> On Sun, Apr 1, 2018 at 9:37 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> I’d bet a warm glass of beer  ( pick up only, no free delivery ) that you
>> will not see them in user level
>> modules ( = something you can fire up)  at a rational price ( < $500)  for
>> quite a while ( = years …).
>> The target market is integration in self driving / autonomous vehicles. If
>> you are GM or Toyota,
>> they will gladly support you. For the rest of us …. go to the back of the
>> line ….. That’s been the pattern
>> on this stuff like this for quite a while.
>> 
>> Bob
>> 
>>> On Apr 1, 2018, at 1:04 PM, Joseph Gray  wrote:
>>> 
>>> Magnus,
>>> 
>>> When I can buy one of these new, multi-frequency receivers, I'll remember
>>> to thank you :-) I wonder if any of the three will be available this
>> year.
>>> The Broadcom chipset in phones will be nice, but I'd also like a
>> standalone
>>> module from anyone. More fun stuff to play with.
>>> 
>>> Joe Gray
>>> W5JG
>>> 
>>> 
>>> On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson <
>> mag...@rubidium.dyndns.org
 wrote:
>>> 
 Hi Joe,
 
 On 03/31/2018 01:16 PM, Joseph Gray wrote:
> I've been reading announcements by Broadcom, uBlox and ST Micro for new
> chipsets that will use L1, L2, L5 to provide significantly more precise
> positioning for every day applications like cell phone, autonomous
> vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says
 "centimeter
> level". The next few years ought to be very interesting, as these
 chipsets
> become available in consumer products.
 
 I have advocated for receivers able to handle multiple frequencies and
 multiple GNSS for some time, sneaking it into documents, so there should
 be some preparations for this now.
 
 The benefit is naturally redundancy, but also higher precision.
 
 Natural I would enjoy cheap multi-frequency receivers myself, but I
 would never admit that this would be a reason for advocating it. ;-)
 
 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
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>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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Re: [time-nuts] GPS ANTENNA

[ew via time-nuts]

Question
Using L/H  what is too much signal 
Bert Kehren
 
In a message dated 4/1/2018 10:54:23 PM Eastern Standard Time, 
david.partri...@perdrix.co.uk writes:

 
 just use a bias tee to feed in the antenna volts :)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani
Sent: 01 April 2018 23:29
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS ANTENNA

An unusual attenuator with a DC pass.

On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge 
 wrote:
> Or use a choke ring survey antenna and an attenuator :)
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
> kb8tq
> Sent: 01 April 2018 14:43
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS ANTENNA
>
> Hi
>
> Indeed, it is *very* easy to put to much gain in front of a timing GNSS 
> receiver. These beasts are trying to dig out a signal that you can’t even see 
> with a spectrum analyzer.
> It’s way to far below the noise floor to detect that way. They optimize 
> things pretty tightly to get that done (and to hit a price target ….). Put to 
> much gain in front of them and they get unhappy.
>
> Making this even more crazy, the survey industry standard antenna *does* have 
> a lot of gain. Survey receivers need way more gain in front of them than 
> timing receivers. Put a survey antenna directly on a timing device and 
> trouble will likely be the outcome. Equally, a survey instrument probably 
> will not be happy with a timing receiver.
>
> Why all this nonsense? As far as I can tell, it goes back to how the very 
> early L1 / L2 survey boxes were designed back in the 1980’s and early 1990’s. 
> They made a basic decision to put a lot of gain at the antenna. Motorola came 
> along with their GPS modules later on. They made a *very* different decision 
> about how to distribute the gain. There are very good arguments on both sides 
> for why they did it this way.
> The bottom line is still - you need to match things up …
>
> Bob
>
>> On Apr 1, 2018, at 2:36 AM, cfo  wrote:
>>
>> On Sat, 31 Mar 2018 10:58:19 -0500,
>> donandarline-Re5JQEeQqe8AvxtiuMwx3w
>> wrote:
>>
>>> I found a supplier for high quality GPS antennas at a very 
>>> reasonable price. PCTEL GPSL1-TMG-SPI-40NCB.
>>
>> *** SNIP ***
>>
>> I had one of those on 25m cable, and it worked fine on a Tbolt , 
>> until i got an active antenna splitter that also had some gain.
>> Then i had to replace it w. a 26dB version of same type, else the 
>> "Jackson Lite" was loosing sync.
>>
>> What i mean here, is that you can get too much gain too.
>>
>> Btw: Good price.
>>
>> CFO
>> Denmark
>>
>> ___
>> 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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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] New GNSS chipsets

[Magnus Danielson]

Hi Hal,

On 04/02/2018 03:47 AM, Hal Murray wrote:
> 
> mag...@rubidium.dyndns.org said:
>> I have advocated for receivers able to handle multiple frequencies and
>> multiple GNSS for some time, sneaking it into documents, so there should be
>> some preparations for this now.
> 
> How well do various GNSS track UTC and/or eachother?

Within a handful of ns from UTC, which is quite good.

GPS masterclock is to be held with +/- 1 us of UTC USNO, but in practice
it is held much tighter, as within 3-5 ns or so. I expect the other
constellations to be in that neighborhood even if not with that low
value. It should be easy to check, but I'm a bit lazy to do so right now.

>> The benefit is naturally redundancy, but also higher precision. 
> 
> I've been assuming the cheap GPS jammers will kill the others too.  Are there 
> any signals far enough away from L1 that they might get through?

The cheap jammers hit L1 C/A. It takes more jammer-cores to cover more
frequencies, and the more frequencies you track, the harder to pinpoint
them all, and well, until full constellation full frequency receivers is
common, jammers will not adapt fully to it.

How well antennas and receivers handle sideband jamming depends on the
receiver design, just as in normal radio setups.

Cheers,
Magnus
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Re: [time-nuts] New GNSS chipsets

[ew via time-nuts]

I think Bob is right and knows what he is talking about.  Example Furuno GT-87, 
how many years have I known about it and tried to buy some, just recently 
became available.
Bert Kehren
 
In a message dated 4/1/2018 10:52:50 PM Eastern Standard Time, jg...@zianet.com 
writes:

 
 Bob,

If it was a glass of good bourbon, I'd take you up on that offer :-)

The Broadcom chipsets are touted as being specifically for phones. Whether
we'll be able to buy stand alone modules, I don't know. The uBlox chipsets
have in that past been widely available at rational prices. Hopefully the
new "9" series will be, also. As for the ST Micro, I haven't a clue, but
considering how their microcontrollers are so widely available from China,
who knows what will happen.

Joe Gray
W5JG


On Sun, Apr 1, 2018 at 9:37 PM, Bob kb8tq  wrote:

> Hi
>
> I’d bet a warm glass of beer ( pick up only, no free delivery ) that you
> will not see them in user level
> modules ( = something you can fire up) at a rational price ( < $500) for
> quite a while ( = years …).
> The target market is integration in self driving / autonomous vehicles. If
> you are GM or Toyota,
> they will gladly support you. For the rest of us …. go to the back of the
> line ….. That’s been the pattern
> on this stuff like this for quite a while.
>
> Bob
>
> > On Apr 1, 2018, at 1:04 PM, Joseph Gray  wrote:
> >
> > Magnus,
> >
> > When I can buy one of these new, multi-frequency receivers, I'll remember
> > to thank you :-) I wonder if any of the three will be available this
> year.
> > The Broadcom chipset in phones will be nice, but I'd also like a
> standalone
> > module from anyone. More fun stuff to play with.
> >
> > Joe Gray
> > W5JG
> >
> >
> > On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson <
> mag...@rubidium.dyndns.org
> >> wrote:
> >
> >> Hi Joe,
> >>
> >> On 03/31/2018 01:16 PM, Joseph Gray wrote:
> >>> I've been reading announcements by Broadcom, uBlox and ST Micro for new
> >>> chipsets that will use L1, L2, L5 to provide significantly more precise
> >>> positioning for every day applications like cell phone, autonomous
> >>> vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says
> >> "centimeter
> >>> level". The next few years ought to be very interesting, as these
> >> chipsets
> >>> become available in consumer products.
> >>
> >> I have advocated for receivers able to handle multiple frequencies and
> >> multiple GNSS for some time, sneaking it into documents, so there should
> >> be some preparations for this now.
> >>
> >> The benefit is naturally redundancy, but also higher precision.
> >>
> >> Natural I would enjoy cheap multi-frequency receivers myself, but I
> >> would never admit that this would be a reason for advocating it. ;-)
> >>
> >> 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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> mailman/listinfo/time-nuts
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Re: [time-nuts] New GNSS chipsets

[Magnus Danielson]

Hi Tom,

It is indeed a benefit to use the different constellations. However, I
want to make one point regarding propagation delay. As you observe one
satellite in 2 frequencies, you can use the fact that the ionospheric
shift at one frequency depends on the frequency and the TEC of that
path. As you now observe on two frequencies, you can now on the
difference between the measures estimate how much the difference of
frequency picked up at TEC, thus one can separate out the TEC effect. By
estimating TEX from those observations, the ionspheric effect can be
removed from both observations. If you try to do this with another
constellation, you add a number of complicating factors and loose
precision as you do so. Can you observe the same satellite in three
frequencies, you can build a more accurate estimation and compensation.
Also, you an loose one of the signals and still be able to perform the
processing. One should be prepared to do L1 only, L2C only, L5 only, L1
& L2C, L1 & L5, L2C & L5 and finally L1 & L2C & L5.

Cheers,
Magnus

On 04/01/2018 11:53 PM, Tom Knox wrote:
> Hi All;
> 
> I think the real break through is using these different constellations and 
> their different frequencies and looking at carrier phase verses timing 
> elements. This should allow the removal of propagation delay.
> 
> Cheers;
> 
> Thomas Knox
> act...@hotmail.com
> 
> 
> 
> From: time-nuts  on behalf of Magnus Danielson 
> 
> Sent: Sunday, April 1, 2018 2:40 PM
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] New GNSS chipsets
> 
> Joe,
> 
> I'm not sure I had much influence, but I at least try to advocate for it
> to become a good market, so hopefully it will be affordable. It has
> actually been affordable for quite some time, so going multifrequency
> should be the next step and with that the benefits.
> 
> Cheers,
> Magnus
> 
> On 04/01/2018 07:04 PM, Joseph Gray wrote:
>> Magnus,
>>
>> When I can buy one of these new, multi-frequency receivers, I'll remember
>> to thank you :-) I wonder if any of the three will be available this year.
>> The Broadcom chipset in phones will be nice, but I'd also like a standalone
>> module from anyone. More fun stuff to play with.
>>
>> Joe Gray
>> W5JG
>>
>>
>> On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson >> wrote:
>>
>>> Hi Joe,
>>>
>>> On 03/31/2018 01:16 PM, Joseph Gray wrote:
 I've been reading announcements by Broadcom, uBlox and ST Micro for new
 chipsets that will use L1, L2, L5 to provide significantly more precise
 positioning for every day applications like cell phone, autonomous
 vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says
>>> "centimeter
 level". The next few years ought to be very interesting, as these
>>> chipsets
 become available in consumer products.
>>>
>>> I have advocated for receivers able to handle multiple frequencies and
>>> multiple GNSS for some time, sneaking it into documents, so there should
>>> be some preparations for this now.
>>>
>>> The benefit is naturally redundancy, but also higher precision.
>>>
>>> Natural I would enjoy cheap multi-frequency receivers myself, but I
>>> would never admit that this would be a reason for advocating it. ;-)
>>>
>>> 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] GPS ANTENNA

[Björn]

Or find an Arra “level set” variable attenuator. 3844 and 3854 models can often 
be found cheaply, have dc-pass and attenuate at both L1 and L2.

/Björn 

Sent from my iPhone

> On 2 Apr 2018, at 03:43, David C. Partridge  
> wrote:
> 
> just use a bias tee to feed in the antenna volts :)
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio 
> Boriani
> Sent: 01 April 2018 23:29
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS ANTENNA
> 
> An unusual attenuator with a DC pass.
> 
>> On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge 
>>  wrote:
>> Or use a choke ring survey antenna and an attenuator :)
>> 
>> Dave
>> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
>> kb8tq
>> Sent: 01 April 2018 14:43
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] GPS ANTENNA
>> 
>> Hi
>> 
>> Indeed, it is *very* easy to put to much gain in front of a timing GNSS 
>> receiver. These beasts are trying to dig out a signal that you can’t even 
>> see with a spectrum analyzer.
>> It’s way to far below the noise floor to detect that way. They optimize 
>> things pretty tightly to get that done (and to hit a price target ….). Put 
>> to much gain in front of them and they get unhappy.
>> 
>> Making this even more crazy, the survey industry standard antenna *does* 
>> have a lot of gain. Survey receivers need way more gain in front of them 
>> than timing receivers. Put a survey antenna directly on a timing device and 
>> trouble will likely be the outcome. Equally, a survey instrument probably 
>> will not be happy with a timing receiver.
>> 
>> Why all this nonsense? As far as I can tell, it goes back to how the very 
>> early L1 / L2 survey boxes were designed back in the 1980’s and early 
>> 1990’s. They made a basic decision to put a lot of gain at the antenna. 
>> Motorola came along with their GPS modules later on. They made a *very* 
>> different decision about how to distribute the gain. There are very good 
>> arguments on both sides for why they did it this way.
>> The bottom line is still - you need to match things up …
>> 
>> Bob
>> 
>>> On Apr 1, 2018, at 2:36 AM, cfo  wrote:
>>> 
>>> On Sat, 31 Mar 2018 10:58:19 -0500,
>>> donandarline-Re5JQEeQqe8AvxtiuMwx3w
>>> wrote:
>>> 
 I found a supplier for high quality GPS antennas at a very 
 reasonable price. PCTEL GPSL1-TMG-SPI-40NCB.
>>> 
>>> *** SNIP ***
>>> 
>>> I had one of those on 25m cable, and it worked fine on a Tbolt , 
>>> until i got an active antenna splitter that also had some gain.
>>> Then i had to replace it w. a 26dB version of same type, else the 
>>> "Jackson Lite" was loosing sync.
>>> 
>>> What i mean here, is that you can get too much gain too.
>>> 
>>> Btw: Good price.
>>> 
>>> CFO
>>> Denmark
>>> 
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