Re: [time-nuts] NIST

[Hal Murray]

pla...@gmail.com said:
> Which satellites?  Most are here:  https://celestrak.com  Tracking programs
> are abundant. 

I was thinking of geo-sync, but if position info is widely available then I 
guess I should be interested in any satellites that provide good time.  (maybe 
an are likely to continue providing good time after some nasty event)


-- 
These are my opinions.  I hate spam.




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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Mark Goldberg]

On Fri, Aug 31, 2018 at 12:41 PM, Gerhard Hoffmann  wrote:

>
>
>> So you can test your hold over behavior with aluminum foil (or your hand)
>> over your antenna
>>
>> OMG, I first read "with aluminium foil hat over your head"
>

Now, foil under the antenna on the other hand, big improvement!


Regards,

Mark
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Re: [time-nuts] Fwd: Re: law and regulation applying to time.. was Re: OOPS on my wwv legal post

[shouldbe q931]

On Fri, Aug 31, 2018 at 10:31 AM Dr. Götz Romahn  wrote:
>
> For German regulations see here:
> https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time.html
> Götz
>
CET is derived from UTC

https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-441/realisation-of-legal-time-in-germany.html

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Re: [time-nuts] News

[Dr. Geophysics]

Congratulations!  Well done!

On Thu, Aug 30, 2018 at 16:40 Magnus Danielson 
wrote:

> Hi Bob,
>
> On 08/30/2018 10:33 PM, Bob kb8tq wrote:
> > Hi
> >
> > Magnus … do you have some news you might want to share with the group?
>
> Oh, well, sure:
>
> Today I received a nice email from IEEE starting with:
> "It is a great pleasure to congratulate you on your elevation to the
> grade of IEEE Senior member. IEEE Senior Membership is an honor bestowed
> only to those who have made significant contributions to the profession."
>
> I'm humbled by these words, but proud of the achievement and happy for
> the distinction. This has been a process that has been going on since
> spring when IEEE approached me and pointed out that I should be able to
> become senior member, writing up a modern CV and then being interviewed
> by three Senior Members was interesting, sharing the room with very
> senior engineers, PhDs and professors all seeking to reach the IEEE
> Senior member elevation.
>
> Cheers,
> Magnus
>
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http://dr.geophysics.googlepages.com
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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

Time is not (ultimately) determined by an atomic clock. It’s determined by 
astronomical observations 
that evaluate the rotation of the planet. Those observations are what drive 
things like leap seconds. 
In the event that a flare takes out 99% of all life on earth and every 
electrical device …. I don’t really 
think we will be worried about it being 12:01:01 PM. What we *will* be 
concerned about is not really
a Time Nut subject. 

To answer the question of how many clocks are there - take a look at how UTC is 
determined by BIH
Paris. The answer is in the “many hundreds”. Yes, 99% of them could go along 
with all the people that 
run them. Again … not really a Time Nut subject. That still leaves quite a few 
to run off of. 

Bob

> On Aug 31, 2018, at 6:38 PM, Dana Whitlow  wrote:
> 
> I'm thinking about if/when "the big one hits" and takes out most or all of
> the GPS
> sats, cell phone systems, etc.
> 
> Then the time required to reboot up to a reasonable level of technology
> might turn
> out to be limited by our ability to determine time and freq somewhat
> accurately.  The
> better we can do from scratch, the faster the reboot.
> 
> So one question is:  how many Cs beam clocks are out there which are kept
> running
> and "on time", at least by frequent logging of errors if not by actual
> setting/tweaking?
> 
> If "the big one" is global nuclear war, of course we'll all have far more
> to worry about
> than keeping our watches accurately set.  But what if it's another
> Carrington-level
> event?  I'm sure we'd all like to get back to business as usual as quickly
> as possible.
> 
> Dana
> 
> 
> On Fri, Aug 31, 2018 at 5:23 PM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> I think we have a little bit of confusion here. WWVB is not going to help
>> anybody navigate.
>> It’s not going to help track people with ankle bracelets or trucks
>> stopping at bars. Car thieves
>> jamming Lojack still happens. Turn iWWVB on or off, this stuff still goes
>> on. None of this is
>> a Time Nuts sort of issue.
>> 
>> The only thing WWVB *might* do is provide timing. That’s very different
>> than navigation. A
>> mobile this or that driving by puts your GPSDO into holdover. It maintains
>> time while it is in
>> holdover. Minutes or hours, possibly days … works the same way. The system
>> keeps running
>> just like GPS was doing fine. If after a day or more, the GPS is still
>> jammed, that single  cell tower
>> shuts down. Take out one cell tower and the system keeps running. There is
>> a lot of overlap on
>> these systems. Towers go down a lot more often than you might think …..
>> 
>> Do all systems work identically in terms of timing? Of course not. If
>> timing is critical to operation,
>> systems do use GPSDO’s. The same basic principles apply. The main question
>> would be one
>> of overlap between elements of the system.
>> 
>> The same jamming that takes out GPS for timing also takes it out for
>> normal navigation. Take
>> it out over an entire city and everybody’s vehicle navigation system goes
>> out. Do that even for
>> a couple of hours and it’s on the evening news. Do that for a day and
>> there *is* a response.
>> That’s the kind of thing needed to impact utility systems (like cell
>> towers) in a significant way.
>> It simply does not happen ….City wide is very hard to do from the ground.
>> From the air, you
>> can get the coverage. It’s tough to keep doing it from the air for days on
>> end.
>> 
>> So, interns of “the world ends if / when WWVB turns off” … not so much.
>> 
>> In terms of the initial question, GPSDO’s in general are pretty good at
>> handling the typical
>> jamming they might run into.
>> 
>> Bob
>> 
>> 
>> 
>>> On Aug 31, 2018, at 3:52 PM, Scott McGrath  wrote:
>>> 
>>> And here is one of the schematics running around the ‘net.   This one is
>> noise based
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On Aug 31, 2018, at 3:41 PM, Gerhard Hoffmann  wrote:
>>> 
>>> 
>>> 
 Am 31.08.2018 um 19:39 schrieb jimlux:
> On 8/31/18 10:15 AM, Bob kb8tq wrote:
> Hi
> 
> Having spent a lot of my life designing GPSDO’s it’s a “that depends”
>> sort of thing.
> For a simple noise jammer, yes, they pretty much all will go into
>> holdover. When the
> jammer goes away, they come out of holdover. There are a few older
>> units that may not
> do quite as well with various sorts of broadband jamming.  With a
>> spoofing jammer that is flying
> around overhead and simulating an entire constellation … you could see
>> any of them do odd
> things. An airborne jammer flying over this or that city likely gets
>> you into a “act of war” sort of issue.
> It’s something you build if you are a nation state.
> 
> The performance with noise jammers is not a guess. It’s based on field
>> experience and
> all those never ending meetings I keep referring to …..
> 
>>> IIRC, there was a truck driver who successfully jammed all those
>> airworthy GPS systems
>>> at SF airport 

Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Scott McGrath]

That’s the scenario i’m most concerned with not war or terrorism but a natural 
event which has occurred before and will occur again.

Rebooting technology will be a heck of a lot easier with a variety of precision 
time/frequency distribution methods.

After a Carrington type event a working Cs or Rb will be worth several times 
their weight in gold.

Its not that I’m nostalgic for the old days but having a HF frequency source 
will allow HF networks to determine propagation .

Content by Scott
Typos by Siri

On Aug 31, 2018, at 6:38 PM, Dana Whitlow  wrote:

I'm thinking about if/when "the big one hits" and takes out most or all of
the GPS
sats, cell phone systems, etc.

Then the time required to reboot up to a reasonable level of technology
might turn
out to be limited by our ability to determine time and freq somewhat
accurately.  The
better we can do from scratch, the faster the reboot.

So one question is:  how many Cs beam clocks are out there which are kept
running
and "on time", at least by frequent logging of errors if not by actual
setting/tweaking?

If "the big one" is global nuclear war, of course we'll all have far more
to worry about
than keeping our watches accurately set.  But what if it's another
Carrington-level
event?  I'm sure we'd all like to get back to business as usual as quickly
as possible.

Dana


> On Fri, Aug 31, 2018 at 5:23 PM Bob kb8tq  wrote:
> 
> Hi
> 
> I think we have a little bit of confusion here. WWVB is not going to help
> anybody navigate.
> It’s not going to help track people with ankle bracelets or trucks
> stopping at bars. Car thieves
> jamming Lojack still happens. Turn iWWVB on or off, this stuff still goes
> on. None of this is
> a Time Nuts sort of issue.
> 
> The only thing WWVB *might* do is provide timing. That’s very different
> than navigation. A
> mobile this or that driving by puts your GPSDO into holdover. It maintains
> time while it is in
> holdover. Minutes or hours, possibly days … works the same way. The system
> keeps running
> just like GPS was doing fine. If after a day or more, the GPS is still
> jammed, that single  cell tower
> shuts down. Take out one cell tower and the system keeps running. There is
> a lot of overlap on
> these systems. Towers go down a lot more often than you might think …..
> 
> Do all systems work identically in terms of timing? Of course not. If
> timing is critical to operation,
> systems do use GPSDO’s. The same basic principles apply. The main question
> would be one
> of overlap between elements of the system.
> 
> The same jamming that takes out GPS for timing also takes it out for
> normal navigation. Take
> it out over an entire city and everybody’s vehicle navigation system goes
> out. Do that even for
> a couple of hours and it’s on the evening news. Do that for a day and
> there *is* a response.
> That’s the kind of thing needed to impact utility systems (like cell
> towers) in a significant way.
> It simply does not happen ….City wide is very hard to do from the ground.
> From the air, you
> can get the coverage. It’s tough to keep doing it from the air for days on
> end.
> 
> So, interns of “the world ends if / when WWVB turns off” … not so much.
> 
> In terms of the initial question, GPSDO’s in general are pretty good at
> handling the typical
> jamming they might run into.
> 
> Bob
> 
> 
> 
>> On Aug 31, 2018, at 3:52 PM, Scott McGrath  wrote:
>> 
>> And here is one of the schematics running around the ‘net.   This one is
> noise based
>> 
>> 
>> 
>> 
>> 
>> On Aug 31, 2018, at 3:41 PM, Gerhard Hoffmann  wrote:
>> 
>> 
>> 
 Am 31.08.2018 um 19:39 schrieb jimlux:
 On 8/31/18 10:15 AM, Bob kb8tq wrote:
 Hi
 
 Having spent a lot of my life designing GPSDO’s it’s a “that depends”
> sort of thing.
 For a simple noise jammer, yes, they pretty much all will go into
> holdover. When the
 jammer goes away, they come out of holdover. There are a few older
> units that may not
 do quite as well with various sorts of broadband jamming.  With a
> spoofing jammer that is flying
 around overhead and simulating an entire constellation … you could see
> any of them do odd
 things. An airborne jammer flying over this or that city likely gets
> you into a “act of war” sort of issue.
 It’s something you build if you are a nation state.
 
 The performance with noise jammers is not a guess. It’s based on field
> experience and
 all those never ending meetings I keep referring to …..
 
>> IIRC, there was a truck driver who successfully jammed all those
> airworthy GPS systems
>> at SF airport trying to hide his private detours, just by passing on the
> highway with
>> El Cheapo hardware.
>> 
>>> 
>>> In effect, a broadband jammer (or, probably, a tone jammer that
> overwhelms the 1 bit ADC receiver) is the same as a "loss of signal" - the
> receiver probably doesn't know the difference - it just drops sync and
> tries to unsuccessfully reacquire.
>> 
>> I think 

Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Dana Whitlow]

I'm thinking about if/when "the big one hits" and takes out most or all of
the GPS
sats, cell phone systems, etc.

Then the time required to reboot up to a reasonable level of technology
might turn
out to be limited by our ability to determine time and freq somewhat
accurately.  The
better we can do from scratch, the faster the reboot.

So one question is:  how many Cs beam clocks are out there which are kept
running
and "on time", at least by frequent logging of errors if not by actual
setting/tweaking?

If "the big one" is global nuclear war, of course we'll all have far more
to worry about
than keeping our watches accurately set.  But what if it's another
Carrington-level
event?  I'm sure we'd all like to get back to business as usual as quickly
as possible.

Dana


On Fri, Aug 31, 2018 at 5:23 PM Bob kb8tq  wrote:

> Hi
>
> I think we have a little bit of confusion here. WWVB is not going to help
> anybody navigate.
> It’s not going to help track people with ankle bracelets or trucks
> stopping at bars. Car thieves
> jamming Lojack still happens. Turn iWWVB on or off, this stuff still goes
> on. None of this is
> a Time Nuts sort of issue.
>
> The only thing WWVB *might* do is provide timing. That’s very different
> than navigation. A
> mobile this or that driving by puts your GPSDO into holdover. It maintains
> time while it is in
> holdover. Minutes or hours, possibly days … works the same way. The system
> keeps running
> just like GPS was doing fine. If after a day or more, the GPS is still
> jammed, that single  cell tower
> shuts down. Take out one cell tower and the system keeps running. There is
> a lot of overlap on
> these systems. Towers go down a lot more often than you might think …..
>
> Do all systems work identically in terms of timing? Of course not. If
> timing is critical to operation,
> systems do use GPSDO’s. The same basic principles apply. The main question
> would be one
> of overlap between elements of the system.
>
> The same jamming that takes out GPS for timing also takes it out for
> normal navigation. Take
> it out over an entire city and everybody’s vehicle navigation system goes
> out. Do that even for
> a couple of hours and it’s on the evening news. Do that for a day and
> there *is* a response.
> That’s the kind of thing needed to impact utility systems (like cell
> towers) in a significant way.
> It simply does not happen ….City wide is very hard to do from the ground.
> From the air, you
> can get the coverage. It’s tough to keep doing it from the air for days on
> end.
>
> So, interns of “the world ends if / when WWVB turns off” … not so much.
>
> In terms of the initial question, GPSDO’s in general are pretty good at
> handling the typical
> jamming they might run into.
>
> Bob
>
>
>
> > On Aug 31, 2018, at 3:52 PM, Scott McGrath  wrote:
> >
> > And here is one of the schematics running around the ‘net.   This one is
> noise based
> >
> > 
> >
> >
> >
> > On Aug 31, 2018, at 3:41 PM, Gerhard Hoffmann  wrote:
> >
> >
> >
> >> Am 31.08.2018 um 19:39 schrieb jimlux:
> >>> On 8/31/18 10:15 AM, Bob kb8tq wrote:
> >>> Hi
> >>>
> >>> Having spent a lot of my life designing GPSDO’s it’s a “that depends”
> sort of thing.
> >>> For a simple noise jammer, yes, they pretty much all will go into
> holdover. When the
> >>> jammer goes away, they come out of holdover. There are a few older
> units that may not
> >>> do quite as well with various sorts of broadband jamming.  With a
> spoofing jammer that is flying
> >>> around overhead and simulating an entire constellation … you could see
> any of them do odd
> >>> things. An airborne jammer flying over this or that city likely gets
> you into a “act of war” sort of issue.
> >>> It’s something you build if you are a nation state.
> >>>
> >>> The performance with noise jammers is not a guess. It’s based on field
> experience and
> >>> all those never ending meetings I keep referring to …..
> >>>
> > IIRC, there was a truck driver who successfully jammed all those
> airworthy GPS systems
> > at SF airport trying to hide his private detours, just by passing on the
> highway with
> > El Cheapo hardware.
> >
> >>
> >> In effect, a broadband jammer (or, probably, a tone jammer that
> overwhelms the 1 bit ADC receiver) is the same as a "loss of signal" - the
> receiver probably doesn't know the difference - it just drops sync and
> tries to unsuccessfully reacquire.
> >
> > I think that Holmes wrote somewhere that the easiest way to jam was a
> carrier quite close
> > to the frequency where the suppressed carrier of the BPSK would be. It
> could be weak because
> > it would have some processing gain, even if not completely sync to the
> rest of the signals.
> > The typical 1 or 2 Bit ADC has no chance to see it separated from the
> rest.
> >
> >>
> >> So you can test your hold over behavior with aluminum foil (or your
> hand) over your antenna
> >>
> > OMG, I first read "with aluminium foil hat over your head"
> >
> > Cheers,
> > 

Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

I think we have a little bit of confusion here. WWVB is not going to help 
anybody navigate. 
It’s not going to help track people with ankle bracelets or trucks stopping at 
bars. Car thieves 
jamming Lojack still happens. Turn iWWVB on or off, this stuff still goes on. 
None of this is 
a Time Nuts sort of issue. 

The only thing WWVB *might* do is provide timing. That’s very different than 
navigation. A 
mobile this or that driving by puts your GPSDO into holdover. It maintains time 
while it is in
holdover. Minutes or hours, possibly days … works the same way. The system 
keeps running
just like GPS was doing fine. If after a day or more, the GPS is still jammed, 
that single  cell tower 
shuts down. Take out one cell tower and the system keeps running. There is a 
lot of overlap on 
these systems. Towers go down a lot more often than you might think …..

Do all systems work identically in terms of timing? Of course not. If timing is 
critical to operation,
systems do use GPSDO’s. The same basic principles apply. The main question 
would be one
of overlap between elements of the system. 

The same jamming that takes out GPS for timing also takes it out for normal 
navigation. Take
it out over an entire city and everybody’s vehicle navigation system goes out. 
Do that even for
a couple of hours and it’s on the evening news. Do that for a day and there 
*is* a response. 
That’s the kind of thing needed to impact utility systems (like cell towers) in 
a significant way. 
It simply does not happen ….City wide is very hard to do from the ground.  From 
the air, you 
can get the coverage. It’s tough to keep doing it from the air for days on end. 

So, interns of “the world ends if / when WWVB turns off” … not so much.

In terms of the initial question, GPSDO’s in general are pretty good at 
handling the typical 
jamming they might run into. 

Bob



> On Aug 31, 2018, at 3:52 PM, Scott McGrath  wrote:
> 
> And here is one of the schematics running around the ‘net.   This one is 
> noise based
> 
> 
> 
> 
> 
> On Aug 31, 2018, at 3:41 PM, Gerhard Hoffmann  wrote:
> 
> 
> 
>> Am 31.08.2018 um 19:39 schrieb jimlux:
>>> On 8/31/18 10:15 AM, Bob kb8tq wrote:
>>> Hi
>>> 
>>> Having spent a lot of my life designing GPSDO’s it’s a “that depends” sort 
>>> of thing.
>>> For a simple noise jammer, yes, they pretty much all will go into holdover. 
>>> When the
>>> jammer goes away, they come out of holdover. There are a few older units 
>>> that may not
>>> do quite as well with various sorts of broadband jamming.  With a spoofing 
>>> jammer that is flying
>>> around overhead and simulating an entire constellation … you could see any 
>>> of them do odd
>>> things. An airborne jammer flying over this or that city likely gets you 
>>> into a “act of war” sort of issue.
>>> It’s something you build if you are a nation state.
>>> 
>>> The performance with noise jammers is not a guess. It’s based on field 
>>> experience and
>>> all those never ending meetings I keep referring to …..
>>> 
> IIRC, there was a truck driver who successfully jammed all those airworthy 
> GPS systems
> at SF airport trying to hide his private detours, just by passing on the 
> highway with
> El Cheapo hardware.
> 
>> 
>> In effect, a broadband jammer (or, probably, a tone jammer that overwhelms 
>> the 1 bit ADC receiver) is the same as a "loss of signal" - the receiver 
>> probably doesn't know the difference - it just drops sync and tries to 
>> unsuccessfully reacquire.
> 
> I think that Holmes wrote somewhere that the easiest way to jam was a carrier 
> quite close
> to the frequency where the suppressed carrier of the BPSK would be. It could 
> be weak because
> it would have some processing gain, even if not completely sync to the rest 
> of the signals.
> The typical 1 or 2 Bit ADC has no chance to see it separated from the rest.
> 
>> 
>> So you can test your hold over behavior with aluminum foil (or your hand) 
>> over your antenna
>> 
> OMG, I first read "with aluminium foil hat over your head"
> 
> Cheers,
> Gerhard
> 
> 
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Re: [time-nuts] NIST

[Hal Murray]

Thanks.

> perigee height:   35772 km
> apogee height:35800 km

If I did the math right, that's 89 microseconds.


-- 
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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Gerhard Hoffmann]

Am 31.08.2018 um 19:39 schrieb jimlux:

On 8/31/18 10:15 AM, Bob kb8tq wrote:

Hi

Having spent a lot of my life designing GPSDO’s it’s a “that depends” 
sort of thing.
For a simple noise jammer, yes, they pretty much all will go into 
holdover. When the
jammer goes away, they come out of holdover. There are a few older 
units that may not
do quite as well with various sorts of broadband jamming.  With a 
spoofing jammer that is flying
around overhead and simulating an entire constellation … you could 
see any of them do odd
things. An airborne jammer flying over this or that city likely gets 
you into a “act of war” sort of issue.

It’s something you build if you are a nation state.

The performance with noise jammers is not a guess. It’s based on 
field experience and

all those never ending meetings I keep referring to …..

IIRC, there was a truck driver who successfully jammed all those 
airworthy GPS systems
at SF airport trying to hide his private detours, just by passing on the 
highway with

El Cheapo hardware.



In effect, a broadband jammer (or, probably, a tone jammer that 
overwhelms the 1 bit ADC receiver) is the same as a "loss of signal" - 
the receiver probably doesn't know the difference - it just drops sync 
and tries to unsuccessfully reacquire.


I think that Holmes wrote somewhere that the easiest way to jam was a 
carrier quite close
to the frequency where the suppressed carrier of the BPSK would be. It 
could be weak because
it would have some processing gain, even if not completely sync to the 
rest of the signals.

The typical 1 or 2 Bit ADC has no chance to see it separated from the rest.



So you can test your hold over behavior with aluminum foil (or your 
hand) over your antenna



OMG, I first read "with aluminium foil hat over your head"

Cheers,
Gerhard


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[time-nuts] NIST

[Mark Sims]

A GPS receiver that supports SBAS, etc will tell you where the sats are.   Some 
only report to 1 degree,  others 0.1 to 0.01 degrees resolution.  The beam with 
of a small dish at GPS freqs is not all that narrow.

Using orbital elements or processing the GNSS ephemeris message will give you a 
result with quite a bit better resolution.

-
>  There is another problem in that area.  How accurately is the location of 
> the 
satellite known?  published?
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Re: [time-nuts] NIST

[jimlux]

On 8/31/18 11:17 AM, Hal Murray wrote:


att...@kinali.ch said:

I have somewhere a paper (which i cannot find currently, sorry) that used a
dish trained at one of the EGNOS satellites and used it as the only source
for timing. IIRC the results were promising, but not spectacular. The problem
being that all the ionospheric and tropospheric ...


There is another problem in that area.  How accurately is the location of the
satellite known?  published?

Geo-sync satellites actually wander around their nominal positions.  How much
does that effect timing?  I've seen figure-8 pictures of the pattern, but I
don't remember any data on elevation changes.



Their orbital elements are published and updated periodically - download 
them off spacetrack or other sources.


Here's an example

The orbit data is extracted from the following two-line orbital elements,

1 43228U 18023A   18243.14094620 -.0224  0-0  0+0 0  9995
2 43228   0.0377  58.1839 0003405  72.7364 229.1178  1.00272082  1950
Epoch (UTC):31 August 2018 03:22:57
Eccentricity:   0.0003405
inclination:0.0377°
perigee height: 35772 km
apogee height:  35800 km
right ascension of ascending node:  58.1839°
argument of perigee:72.7364°
revolutions per day:1.00272082
mean anomaly at epoch:  229.1178°
orbit number at epoch:  195














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Re: [time-nuts] NIST

[Hal Murray]

att...@kinali.ch said:
> I have somewhere a paper (which i cannot find currently, sorry) that used a
> dish trained at one of the EGNOS satellites and used it as the only source
> for timing. IIRC the results were promising, but not spectacular. The problem
> being that all the ionospheric and tropospheric ...

There is another problem in that area.  How accurately is the location of the 
satellite known?  published?

Geo-sync satellites actually wander around their nominal positions.  How much 
does that effect timing?  I've seen figure-8 pictures of the pattern, but I 
don't remember any data on elevation changes.





-- 
These are my opinions.  I hate spam.




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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

Most of them are doing CW signal detection and notch filtering. There are a 
number 
of ways for “birdies” to show up in any environment, jamming or no jamming. 
Some of
the details of who’s doing what and how well are under NDA. None of it is 100%
effective, it’s just a way to get another 10, 20 or 30 db of margin at this or 
that offset 
from carrier. 

Bob

> On Aug 31, 2018, at 1:36 PM, Mark Sims  wrote:
> 
> Several GPS receivers have a setting for enabling jamming detection and/or 
> mitigation.   The datasheets don't tend to talk about what it does.  But, if 
> the receiver supports it (Trimble and Venus devices), Lady Heather can 
> configure it.
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Re: [time-nuts] NIST

[jimlux]

On 8/31/18 10:31 AM, Brooke Clarke wrote:

Hi Azelio:

Thanks for the link.
It's interesting that their setup (a Ku band satellite TV antenna and a 
standard GPS timing antenna) worked as well as it did with reversed 
polarity.  Does anyone know of a source of reverse polarity GPS antennas 
and a GPS timing receiver that also processes WAAS signals?



you could wind your own helix - it's pretty non critical.
or just use linear pol, and take the 3dB hit. I'll bet the EGNOS + small 
dish has enough gain to make up for it. (but the gain of a dish that is 
a few lambda across isn't huge)




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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[jimlux]

On 8/31/18 10:15 AM, Bob kb8tq wrote:

Hi

Having spent a lot of my life designing GPSDO’s it’s a “that depends” sort of 
thing.
For a simple noise jammer, yes, they pretty much all will go into holdover. 
When the
jammer goes away, they come out of holdover. There are a few older units that 
may not
do quite as well with various sorts of broadband jamming.  With a spoofing 
jammer that is flying
around overhead and simulating an entire constellation … you could see any of 
them do odd
things. An airborne jammer flying over this or that city likely gets you into a 
“act of war” sort of issue.
It’s something you build if you are a nation state.

The performance with noise jammers is not a guess. It’s based on field 
experience and
all those never ending meetings I keep referring to …..




In effect, a broadband jammer (or, probably, a tone jammer that 
overwhelms the 1 bit ADC receiver) is the same as a "loss of signal" - 
the receiver probably doesn't know the difference - it just drops sync 
and tries to unsuccessfully reacquire.


So you can test your hold over behavior with aluminum foil (or your 
hand) over your antenna


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[time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Mark Sims]

Several GPS receivers have a setting for enabling jamming detection and/or 
mitigation.   The datasheets don't tend to talk about what it does.  But, if 
the receiver supports it (Trimble and Venus devices), Lady Heather can 
configure it.
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Re: [time-nuts] NIST

[Brooke Clarke]

Hi Azelio:

Thanks for the link.
It's interesting that their setup (a Ku band satellite TV antenna and a standard GPS timing antenna) worked as well as 
it did with reversed polarity.  Does anyone know of a source of reverse polarity GPS antennas and a GPS timing receiver 
that also processes WAAS signals?


--
Have Fun,

Brooke Clarke
https://www.PRC68.com
https://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how 
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

 Original Message 

Maybe this one is equivalent?

On Fri, Aug 31, 2018 at 4:55 PM Attila Kinali  wrote:

On Thu, 30 Aug 2018 18:54:17 -0700
Brooke Clarke  wrote:


I wonder if anyone has tried using a small parabolic dish, like used for Free 
To Air satellite TV and aimed it at a GPS
satellite track or at a WAAS geostationary satellite using a feed antenna with 
reverse polarization from a normal GPS
antenna?

I have somewhere a paper (which i cannot find currently, sorry) that
used a dish trained at one of the EGNOS satellites and used it as the
only source for timing. IIRC the results were promising, but not
spectacular. The problem being that all the ionospheric and tropospheric
effects limited the performance, which also could not be averaged
over several satellites. Hence most people today focus on whole
constelation systems and try to get the best out of that, even under
multipath and jamming.

 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, Neal Stephenson

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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

Well if you have a magic piece of code that will do the trick, why don’t you 
share it with the 
rest of us? In …. errr …. 50+ years of looking at the problem, nobody else 
seems to have
come up with an answer. It’s not because people have not tried. They’ve been 
working on 
this sort of thing since at least the 60’s. It was at the heart of some really 
big problems the
DOD had with HF and VLF links.  They poured some massive chunks of money into 
it. 

Bob

> On Aug 31, 2018, at 12:30 PM, Scott McGrath  wrote:
> 
> Strangely enough there are these devices called ‘computers’ which are rumored 
> to be able to perform measurements and mathematical calculations.
> 
> One of these ‘computers’ might be profitably employed to perform the 
> necessary measurements calculations and deliver a useful output,   
> 
> Employing a Mentat would be expensive for this task...
> 
> 
> On Aug 31, 2018, at 11:37 AM, Tom Holmes  wrote:
> 
> Uh, folks...Would the apparently still on hiatus TVB approve of this on-going 
> Urinary Olympiad? Just asking. And hoping post this won’t start another one.
> 
> Tom Holmes, N8ZM
> 
> -Original Message-
> From: time-nuts  On Behalf Of Bob kb8tq
> Sent: Friday, August 31, 2018 11:16 AM
> To: Martin VE3OAT ; Discussion of precise time and frequency 
> measurement 
> Subject: Re: [time-nuts] WWV and legal issues
> 
> Hi
> 
> That works fine if you are doing things manual to check a local standard. If 
> you are trying to 
> disipline a few thousand cell towers 24 hours a day … not so much. It also 
> works for 
> checking frequency. What modern systems need is time. That gets you into a 
> whole 
> world of resolving and identifying individual edges. The WWVB signal really 
> was never
> set up for this. Loran-C is an example of a signal that was designed to 
> identify a specific
> edge.
> 
> Bob
> 
>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT  wrote:
>> 
>> But the diurnal phase shifts at VLF are predictable and largely repeatable.  
>> Ignore the phase at night and use only the phase records during the day when 
>> an all-daylight propagation path exists.  You might have to "correct" the 
>> absolute phase reading by some multiple of the RF period, but with a low 
>> rate of local standard oscillator drift, this is a simple matter of 
>> arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field 
>> sites from my office and could maintain phase continuity for weeks at a 
>> time, until we had to diddle the dial on one or several of them to correct 
>> for crystal aging.  Then it was just more arithmetic again.  Several of the 
>> oscillators had such low drift rates that all I needed was one daily phase 
>> reading from the VLF phase tracking receiver (Tracor 599Js) at those sites 
>> to know the frequency of the Sulzers there.
>> 
>> ... Martin VE3OAT
>> 
>> On Thu, 30 Aug 2018 12:27:12 -0400
>> Bob kb8tq  wrote:
>> 
>>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>>> stable signal. As soon as
>>> that signal hits the real world things start to degrade. Propagation 
>>> between transmit and receive sites
>>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade 
>>> noise at 60 KHz. The receive
>>> signal to noise will never be as good as you might like it to be ?.
>> 
>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>> causes a phase shift of several 100?s at even moderate distances
>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>>   Attila Kinali
>> 
>> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

It’s back in the FCS archives. I don’t think it’s one of the ones you can hit 
without going through a
paywall. It was a fun paper to attend. The chatter in the room was 
“interesting” to say the least.

Bob

> On Aug 31, 2018, at 1:07 PM, Brooke Clarke  wrote:
> 
> Hi Bob:
> 
> Do you have and info on that article that would allow me to read it?
> 
> -- 
> Have Fun,
> 
> Brooke Clarke
> https://www.PRC68.com
> https://www.end2partygovernment.com/2012Issues.html
> axioms:
> 1. The extent to which you can fix or improve something will be limited by 
> how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
> 
>  Original Message 
>> Hi
>> 
>> The original “we cracked GPS” paper back in the 1980’s (that unlimitedly 
>> lead to the end of SA)
>> used a medium sized dish ( think of the good old C-band antennas) to pick 
>> out a single sat.
>> 
>> Bob
>> 
>>> On Aug 30, 2018, at 9:54 PM, Brooke Clarke  wrote:
>>> 
>>> Hi Gregory:
>>> 
>>> I wonder if anyone has tried using a small parabolic dish, like used for 
>>> Free To Air satellite TV and aimed it at a GPS satellite track or at a WAAS 
>>> geostationary satellite using a feed antenna with reverse polarization from 
>>> a normal GPS antenna?
>>> http://www.prc68.com/I/FTA.shtml
>>> 
>>> -- 
>>> Have Fun,
>>> 
>>> Brooke Clarke
>>> https://www.PRC68.com
>>> https://www.end2partygovernment.com/2012Issues.html
>>> axioms:
>>> 1. The extent to which you can fix or improve something will be limited by 
>>> how well you understand how it works.
>>> 2. Everybody, with no exceptions, holds false beliefs.
>>> 
>>>  Original Message 
 On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke  wrote:
> I would disagree in that ease of jamming/spoofing is strongly related to 
> wavelength.  That's because antenna efficiency
> goes down as the size of the antenna gets smaller than 1/4 wave.
> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 
> wavelength is a few inches, something that  you can
> hold in your hand.
 However, the short wavelengths of GPS make beam forming a reasonable
 countermeasure against jamming.
 
 By having a small array of GPS antennas a receiver can digitally form
 beams that both aim directly at the relevant satellites (so even
 reducing intersatellite interference) while also steering a deep null
 in the direction of the jammer.  If the jammer is powerful enough to
 overload the front-end then this won't help, but against a
 non-targeted area denying jammer it should be fairly effective.
 
 There are many papers on GNSS beamforming. ( e.g.
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ )
 
 This kind of anti-jamming solution should even be pretty inexpensive
 -- really no more than the cost of N receivers. Except that it is
 specialized technology and thus very expensive. :)
 
 Seeing some open source software implementing beam-forming was one of
 the things I hoped to see result from the open hardware multi-band
 GNSS receivers like the GNSS firehose project (
 http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
 you're going through the trouble of running three coherent receivers
 for three bands, stacking three more of them and locking them to the
 same clock doesn't seem like a big engineering challenge... and the
 rest is just DSP work.
 
 Even absent fancy beam forming, for GNSS timing with a surveyed
 position except at high latitudes it should be possible to use a
 relatively high gain antenna pointed straight up and by doing so blind
 yourself to terrestrial jammers at a cost of fewer SVs being
 available. But I've never tried it.
 
 In an urban area I noticed my own GPSDOs losing signal multiple times
 per week. Monitoring with an SDR showed what appeared to be jammers.
 
 As others have noted intermittent jamming is pretty benign to a GPSDO.
 Spoofing, OTOH, can trivially mess up the timing.  It's my view that
 if you need timing for a security critical purpose there isn't really
 any GNSS based solution commercially available to the general public
 right now, the best bet is a local atomic reference with a GPSDO used
 to monitor and initially set it.
 
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>> 
>> 

Re: [time-nuts] GNSS beam forming

[jimlux]

On 8/31/18 9:38 AM, Gregory Maxwell wrote:

On Fri, Aug 31, 2018 at 2:56 PM Attila Kinali  wrote:

"Just DSP work" is a tad bit more than you think. You are dealing
with sevaral 1Msps of data, even for a simple L1 C/A receiver.
If you are going multi-band-multi-GNSS you are usually in the 50MHz BW
at L1 and 80MHz BW at L2/L5 range, which means you are dealing with
something in the order of 100Msps of data per channel (either as
a single stream of sample or two streams of samples with half rate).


I have done beamforming in software for wifi signals, which is quite
similar a task.

You are probably underestimating somewhat how fast modern systems have
become.  There are now people using GPUs for SDR now as well, which is
perhaps more fitting to a GNSS timestamper than many other SDR
applications, since that application doesn't need to be low latency.
There are now consumer GPUs that do 14 trillion single precision
multiply-adds per second.


Then you add to it that you will need at least 4bit ADCs to get
somewhat jaming proof, probably even 10bit or more and suddenly


There I agree.  It seems to me that a interesting architecture would
be to run a sinusoid killer on a FPGA immediately behind the DACs,
then spit out a 2 or 4 bit stream.






AJ is a slightly different problem than straight up beamforming

You need N+1 receivers to suppress N point source jammers - it's more of 
an adaptive canceller than a beamformer.


The literature has been around since the 60s on how to do this in a 
variety of cases and signals, with plenty of hardware demonstrations 
over the decades ranging from analog combiners to very sophisticated 
digital approaches using algorithms like ESPRIT or MUSIC.


There's also extensive work on AJ techniques for PN signals, although I 
don't know how much is in the open literature.


One wants to think about the jamming/interference signal

In general, you're probably not going to design to "notch" a sinusoid - 
sure that might be a common jammer, but the sinewave generated by the 
jammer might be very noisy and unstable in frequency - sort of the 
opposite of the sinusoids desired by list members :) - the spurious 
oscillation of the TV antenna amplifier was in this bucket.


The jamming signal is likely to be somewhat broadband = pulsed, or 
harmonics of some lower frequency signal, which is none too clean - most 
power supply designers do not lock their PWM rate to a maser, after all.


If you're talking about a sophisticated jammer - typically they'll 
attack some design feature - For instance, way back (more than 50 
years), a strategy for radars was to transmit two tones separated by 
60MHz (Radar IF chains were at 60 MHz) and pulse it, in hopes that you'd 
hose up the AGC, or create intermods. Similarly, transmitting on some 
ham bands in the  50s would get into the TV receiver IF.


Then you get into sophisticated approaches which are more like spoofing 
- transmit a PN modulated signal that replicates the desired signal, 
then pull it away and turn off, forcing the receiver to be in 
"acquisition" mode all the time.


Can you build a receiver which is immune to all of these and sell it for 
$10?  Probably not.  Can you do it for $100-1000, almost certainly.


So now it comes down to the classic tradeoff - what is the value of the 
thing you are protecting.



On time-nuts, we're used to "better performance for its own sake" - it's 
cool, it's nifty, it's educational, for most of us, we don't necessarily 
have to justify our desire to get that next digit. We're also often very 
thrifty - as part of the challenge - I know I can get accuracy X by 
spending $100k, but can I get there spending only $200.


The commercial world, which has to consider the slings and arrows of 
these threats does put a value on it, and that drives the budgets for 
the fixes.  I would venture that *in most cases*, the cost of a fancy 
holdover GPSDO is a tiny, tiny part of the cost of a cell site - 
Installation of the concrete pad for the tower probably costs more.


Sure, if you've got 1000 sites, and you need to upgrade them all at 
$10k/each, that's a $10M hit you need to explain to the shareholders, 
but, it *is* a cost of doing business.


And, realistically, it's much more likely your network failure will be 
because some idiot dug in the wrong place, or someone rolled out a 
software update with a bug, rather than a freak ionization event 
blocking GPS.


Check out the telephone switch bug that shutdown phone service for a day 
in 1990 -

https://users.csc.calpoly.edu/~jdalbey/SWE/Papers/att_collapse.html






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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

Having spent a lot of my life designing GPSDO’s it’s a “that depends” sort of 
thing. 
For a simple noise jammer, yes, they pretty much all will go into holdover. 
When the
jammer goes away, they come out of holdover. There are a few older units that 
may not
do quite as well with various sorts of broadband jamming.  With a spoofing 
jammer that is flying
around overhead and simulating an entire constellation … you could see any of 
them do odd 
things. An airborne jammer flying over this or that city likely gets you into a 
“act of war” sort of issue. 
It’s something you build if you are a nation state. 

The performance with noise jammers is not a guess. It’s based on field 
experience and
all those never ending meetings I keep referring to …..

Bob

> On Aug 31, 2018, at 12:04 PM, Mark Spencer  wrote:
> 
> Hi:
> 
> I'm curious if anyone knows how typical GPSDO's are likely to respond to 
> simple GPS jammers ?  Could the GPSDO be reasonably expected to go into hold 
> over ?
> 
> The use case I am thinking is along the lines of:
> 
> -A commercial operation relies on a GPSDO for timing at a remote site.  
> 
> -A vehicle with a simple GPS jammer (perhaps intended by the vehicle driver 
> to defeat a GPS tracking system installed near the vehicle) parks near the 
> GPS antenna.
> 
> I'm thinking one likely outcome is the GPSDO goes into hold over and when the 
> vehicle moves away it exits hold over ?   This is all just speculation on my 
> part.
> 
> Comments ?
> 
> Thanks 
> Mark Spencer
> 
> m...@alignedsolutions.com
> 604 762 4099
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Re: [time-nuts] NIST

[Brooke Clarke]

Hi Bob:

Do you have and info on that article that would allow me to read it?

--
Have Fun,

Brooke Clarke
https://www.PRC68.com
https://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how 
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

 Original Message 

Hi

The original “we cracked GPS” paper back in the 1980’s (that unlimitedly lead 
to the end of SA)
used a medium sized dish ( think of the good old C-band antennas) to pick out a 
single sat.

Bob


On Aug 30, 2018, at 9:54 PM, Brooke Clarke  wrote:

Hi Gregory:

I wonder if anyone has tried using a small parabolic dish, like used for Free 
To Air satellite TV and aimed it at a GPS satellite track or at a WAAS 
geostationary satellite using a feed antenna with reverse polarization from a 
normal GPS antenna?
http://www.prc68.com/I/FTA.shtml

--
Have Fun,

Brooke Clarke
https://www.PRC68.com
https://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how 
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

 Original Message 

On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke  wrote:

I would disagree in that ease of jamming/spoofing is strongly related to 
wavelength.  That's because antenna efficiency
goes down as the size of the antenna gets smaller than 1/4 wave.
So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 wavelength 
is a few inches, something that  you can
hold in your hand.

However, the short wavelengths of GPS make beam forming a reasonable
countermeasure against jamming.

By having a small array of GPS antennas a receiver can digitally form
beams that both aim directly at the relevant satellites (so even
reducing intersatellite interference) while also steering a deep null
in the direction of the jammer.  If the jammer is powerful enough to
overload the front-end then this won't help, but against a
non-targeted area denying jammer it should be fairly effective.

There are many papers on GNSS beamforming. ( e.g.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ )

This kind of anti-jamming solution should even be pretty inexpensive
-- really no more than the cost of N receivers. Except that it is
specialized technology and thus very expensive. :)

Seeing some open source software implementing beam-forming was one of
the things I hoped to see result from the open hardware multi-band
GNSS receivers like the GNSS firehose project (
http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
you're going through the trouble of running three coherent receivers
for three bands, stacking three more of them and locking them to the
same clock doesn't seem like a big engineering challenge... and the
rest is just DSP work.

Even absent fancy beam forming, for GNSS timing with a surveyed
position except at high latitudes it should be possible to use a
relatively high gain antenna pointed straight up and by doing so blind
yourself to terrestrial jammers at a cost of fewer SVs being
available. But I've never tried it.

In an urban area I noticed my own GPSDOs losing signal multiple times
per week. Monitoring with an SDR showed what appeared to be jammers.

As others have noted intermittent jamming is pretty benign to a GPSDO.
Spoofing, OTOH, can trivially mess up the timing.  It's my view that
if you need timing for a security critical purpose there isn't really
any GNSS based solution commercially available to the general public
right now, the best bet is a local atomic reference with a GPSDO used
to monitor and initially set it.

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Re: [time-nuts] GNSS beam forming (was: NIST)

[Gregory Maxwell]

On Fri, Aug 31, 2018 at 2:56 PM Attila Kinali  wrote:
> "Just DSP work" is a tad bit more than you think. You are dealing
> with sevaral 1Msps of data, even for a simple L1 C/A receiver.
> If you are going multi-band-multi-GNSS you are usually in the 50MHz BW
> at L1 and 80MHz BW at L2/L5 range, which means you are dealing with
> something in the order of 100Msps of data per channel (either as
> a single stream of sample or two streams of samples with half rate).

I have done beamforming in software for wifi signals, which is quite
similar a task.

You are probably underestimating somewhat how fast modern systems have
become.  There are now people using GPUs for SDR now as well, which is
perhaps more fitting to a GNSS timestamper than many other SDR
applications, since that application doesn't need to be low latency.
There are now consumer GPUs that do 14 trillion single precision
multiply-adds per second.

> Then you add to it that you will need at least 4bit ADCs to get
> somewhat jaming proof, probably even 10bit or more and suddenly

There I agree.  It seems to me that a interesting architecture would
be to run a sinusoid killer on a FPGA immediately behind the DACs,
then spit out a 2 or 4 bit stream.

The best processing tool I have for estimating sinusoid parameters is
https://arxiv.org/abs/1602.05900  the computationally hungry parts
(measuring correlations with candidate sinusoids and the signal) are
easily implemented on an FPGA but still would be pretty impressive to
see running at 50msps. For GNSS applications something far stupider
probably is adequate: FFTs on windowed overlapping blocks, null out
outlying peaks and ifft.  It would not take a very large FFT to get
enough frequency selectivity to kill only 1% of signal power per
eliminated sinusoid-- maybe 256 samples.

> you are dealing with 200-400Mbyte/s data per antenna. Constantly.
> To be able to do reasonable beam forming, you probably need a 4 by 4
> grid at least, that makes 16 antennas which brings us into the

There are many papers showing interesting GNSS beamforming results
with far fewer antennas:

4 antennas, 14-bit, 40msps, and a GPU based decoder:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3231503/pdf/sensors-11-08966.pdf

This one has simulated polar patterns for 7 antennas that look pretty
impressive 
https://web.stanford.edu/group/scpnt/gpslab/pubs/papers/DeLorenzo_IONGNSS_2004.pdf

This one has measurements with 7 antennas on actual hardware:
https://pdfs.semanticscholar.org/5531/aa89f81e4cdfa15e74e98c264dcb697395ca.pdf
(and also talks a bit about their SSE correlators needed to get
realtime performance in a software implementation).

> You still need the lower satellites to survey your position accurately.

Yes, but that is potentially a one time operation.

> Also, going from ~10 birds in view down to ~5 means that
> your PPS jitter just increased by a factor of 5 to 10.
> (source: experiment i've done here some time ago)

But, if your SNR on those 5 remaining birds increases substantially
from increased antenna gain might it not offset some of that loss? I
would worry that getting a consistent phase center on some weird high
gain antenna design would be hard, however.

> There is a reason why Microsemi is building more 5071 these days than
> ever before (rumors have it that they are are 3-4 devices per week).

If you consider the cost of a new 5071 ... that would pay for a heck
of a beam-forming anti-jamming receiver-- at least hardware wise. :)

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Re: [time-nuts] WWV and legal issues

[Scott McGrath]

Strangely enough there are these devices called ‘computers’ which are rumored 
to be able to perform measurements and mathematical calculations.

One of these ‘computers’ might be profitably employed to perform the necessary 
measurements calculations and deliver a useful output,   

Employing a Mentat would be expensive for this task...


On Aug 31, 2018, at 11:37 AM, Tom Holmes  wrote:

Uh, folks...Would the apparently still on hiatus TVB approve of this on-going 
Urinary Olympiad? Just asking. And hoping post this won’t start another one.

Tom Holmes, N8ZM

-Original Message-
From: time-nuts  On Behalf Of Bob kb8tq
Sent: Friday, August 31, 2018 11:16 AM
To: Martin VE3OAT ; Discussion of precise time and frequency 
measurement 
Subject: Re: [time-nuts] WWV and legal issues

Hi

That works fine if you are doing things manual to check a local standard. If 
you are trying to 
disipline a few thousand cell towers 24 hours a day … not so much. It also 
works for 
checking frequency. What modern systems need is time. That gets you into a 
whole 
world of resolving and identifying individual edges. The WWVB signal really was 
never
set up for this. Loran-C is an example of a signal that was designed to 
identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT  wrote:
> 
> But the diurnal phase shifts at VLF are predictable and largely repeatable.  
> Ignore the phase at night and use only the phase records during the day when 
> an all-daylight propagation path exists.  You might have to "correct" the 
> absolute phase reading by some multiple of the RF period, but with a low rate 
> of local standard oscillator drift, this is a simple matter of arithmetic. 
> Back in the day, I managed Sulzer crystal oscillators at 5 field sites from 
> my office and could maintain phase continuity for weeks at a time, until we 
> had to diddle the dial on one or several of them to correct for crystal 
> aging.  Then it was just more arithmetic again.  Several of the oscillators 
> had such low drift rates that all I needed was one daily phase reading from 
> the VLF phase tracking receiver (Tracor 599Js) at those sites to know the 
> frequency of the Sulzers there.
> 
> ... Martin VE3OAT
> 
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq  wrote:
> 
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>> stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between 
>> transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade 
>> noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
> 
>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>Attila Kinali
> 
> 
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[time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Mark Spencer]

Hi:

I'm curious if anyone knows how typical GPSDO's are likely to respond to simple 
GPS jammers ?  Could the GPSDO be reasonably expected to go into hold over ?

The use case I am thinking is along the lines of:

-A commercial operation relies on a GPSDO for timing at a remote site.  

-A vehicle with a simple GPS jammer (perhaps intended by the vehicle driver to 
defeat a GPS tracking system installed near the vehicle) parks near the GPS 
antenna.

I'm thinking one likely outcome is the GPSDO goes into hold over and when the 
vehicle moves away it exits hold over ?   This is all just speculation on my 
part.

Comments ?

Thanks 
Mark Spencer

m...@alignedsolutions.com
604 762 4099
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Re: [time-nuts] NIST

[Azelio Boriani]

Maybe this one is equivalent?

On Fri, Aug 31, 2018 at 4:55 PM Attila Kinali  wrote:
>
> On Thu, 30 Aug 2018 18:54:17 -0700
> Brooke Clarke  wrote:
>
> > I wonder if anyone has tried using a small parabolic dish, like used for 
> > Free To Air satellite TV and aimed it at a GPS
> > satellite track or at a WAAS geostationary satellite using a feed antenna 
> > with reverse polarization from a normal GPS
> > antenna?
>
> I have somewhere a paper (which i cannot find currently, sorry) that
> used a dish trained at one of the EGNOS satellites and used it as the
> only source for timing. IIRC the results were promising, but not
> spectacular. The problem being that all the ionospheric and tropospheric
> effects limited the performance, which also could not be averaged
> over several satellites. Hence most people today focus on whole
> constelation systems and try to get the best out of that, even under
> multipath and jamming.
>
> 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, Neal Stephenson
>
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Re: [time-nuts] WWV and legal issues

[Tom Holmes]

Uh, folks...Would the apparently still on hiatus TVB approve of this on-going 
Urinary Olympiad? Just asking. And hoping post this won’t start another one.

Tom Holmes, N8ZM

-Original Message-
From: time-nuts  On Behalf Of Bob kb8tq
Sent: Friday, August 31, 2018 11:16 AM
To: Martin VE3OAT ; Discussion of precise time and frequency 
measurement 
Subject: Re: [time-nuts] WWV and legal issues

Hi

That works fine if you are doing things manual to check a local standard. If 
you are trying to 
disipline a few thousand cell towers 24 hours a day … not so much. It also 
works for 
checking frequency. What modern systems need is time. That gets you into a 
whole 
world of resolving and identifying individual edges. The WWVB signal really was 
never
set up for this. Loran-C is an example of a signal that was designed to 
identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT  wrote:
> 
> But the diurnal phase shifts at VLF are predictable and largely repeatable.  
> Ignore the phase at night and use only the phase records during the day when 
> an all-daylight propagation path exists.  You might have to "correct" the 
> absolute phase reading by some multiple of the RF period, but with a low rate 
> of local standard oscillator drift, this is a simple matter of arithmetic. 
> Back in the day, I managed Sulzer crystal oscillators at 5 field sites from 
> my office and could maintain phase continuity for weeks at a time, until we 
> had to diddle the dial on one or several of them to correct for crystal 
> aging.  Then it was just more arithmetic again.  Several of the oscillators 
> had such low drift rates that all I needed was one daily phase reading from 
> the VLF phase tracking receiver (Tracor 599Js) at those sites to know the 
> frequency of the Sulzers there.
> 
> ... Martin VE3OAT
> 
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq  wrote:
> 
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>> stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between 
>> transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade 
>> noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
> 
> > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>  Attila Kinali
> 
> 
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Re: [time-nuts] Possible End of Daylight Savings Time in Europe?

[Bob kb8tq]

Hi

Here in the US, we have been creeping along getting rid of daylight time. At 
the rate we have been 
changing the magic dates, I’d bet we have it gone in a few hundred years :)

Bob

> On Aug 31, 2018, at 8:57 AM, John Franke  wrote:
> 
> See: 
> https://www.msn.com/en-us/news/world/europe-ticks-closer-to-ending-daylight-saving-time/ar-BBMGU2d?ocid=spartandhp
> 
> John  WA4WDL


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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

That works fine if you are doing things manual to check a local standard. If 
you are trying to 
disipline a few thousand cell towers 24 hours a day … not so much. It also 
works for 
checking frequency. What modern systems need is time. That gets you into a 
whole 
world of resolving and identifying individual edges. The WWVB signal really was 
never
set up for this. Loran-C is an example of a signal that was designed to 
identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT  wrote:
> 
> But the diurnal phase shifts at VLF are predictable and largely repeatable.  
> Ignore the phase at night and use only the phase records during the day when 
> an all-daylight propagation path exists.  You might have to "correct" the 
> absolute phase reading by some multiple of the RF period, but with a low rate 
> of local standard oscillator drift, this is a simple matter of arithmetic. 
> Back in the day, I managed Sulzer crystal oscillators at 5 field sites from 
> my office and could maintain phase continuity for weeks at a time, until we 
> had to diddle the dial on one or several of them to correct for crystal 
> aging.  Then it was just more arithmetic again.  Several of the oscillators 
> had such low drift rates that all I needed was one daily phase reading from 
> the VLF phase tracking receiver (Tracor 599Js) at those sites to know the 
> frequency of the Sulzers there.
> 
> ... Martin VE3OAT
> 
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq  wrote:
> 
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>> stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between 
>> transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade 
>> noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
> 
> > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>  Attila Kinali
> 
> 
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Re: [time-nuts] GNSS beam forming (was: NIST)

[Scott McGrath]

I/We track down things that jam weather radars.  Mostly WiFi access points 
misconfigured.   

Which share many of the characteristics of GPS jammers

1 - small low powered
2 - one can ruin a pilots entire day
3 - distributed
4 - can literally be anywhere

Stuff like this is why FCC blocked anyone but chip manufacturers from updating 
WiFi radio firmware.

The overwhelming majority of the mods were attempts to improve performance.   
But the firmware hackers were unaware of the band sharing and also did not 
understand that signal characteristics need to be closely controlled and the 
limits the FCC applies are not there to ‘ruin my performance’ but to allow 
others to play nicely in that sandbox.

So many things in life should have been learned in kindergarten.  Sadly many 
have forgotten those lessons.

On Aug 31, 2018, at 10:55 AM, Attila Kinali  wrote:

On Thu, 30 Aug 2018 23:05:48 +
Gregory Maxwell  wrote:


> Seeing some open source software implementing beam-forming was one of
> the things I hoped to see result from the open hardware multi-band
> GNSS receivers like the GNSS firehose project (
> http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
> you're going through the trouble of running three coherent receivers
> for three bands, stacking three more of them and locking them to the
> same clock doesn't seem like a big engineering challenge... and the
> rest is just DSP work.

"Just DSP work" is a tad bit more than you think. You are dealing
with sevaral 1Msps of data, even for a simple L1 C/A receiver.
If you are going multi-band-multi-GNSS you are usually in the 50MHz BW
at L1 and 80MHz BW at L2/L5 range, which means you are dealing with
something in the order of 100Msps of data per channel (either as
a single stream of sample or two streams of samples with half rate).
Then you add to it that you will need at least 4bit ADCs to get
somewhat jaming proof, probably even 10bit or more and suddenly
you are dealing with 200-400Mbyte/s data per antenna. Constantly.
To be able to do reasonable beam forming, you probably need a 4 by 4
grid at least, that makes 16 antennas which brings us into the
3Gbyte/s to 6Gbyte/s region. And that's just the raw _input_ datarate 
you have to handle  A modern GNSS receiver has something in the
order of 50-100 correlators per band, each of which needs to receive 
the full data rate mentioned above. So inside the chip, the data rate
gets multiplied as well.

Now take into considerations that beside running the correlators,
after you phase shifted and weighted the inputs correctly, you
have to run some fancy algorithms (on the raw data) to figure
out what these phase shifts and weights are. For each satellite
you are tracking individually. All this toghether means you have
run some pretty heavy computation, that is very likely not going
to fit into an FPGA, so you need to build a custom ASIC.



> Even absent fancy beam forming, for GNSS timing with a surveyed
> position except at high latitudes it should be possible to use a
> relatively high gain antenna pointed straight up and by doing so blind
> yourself to terrestrial jammers at a cost of fewer SVs being
> available. But I've never tried it.

You still need the lower satellites to survey your position accurately.
Besides that you lose a lot of in terms of timing accuracy, if you
have only a limited number of satellites. So you cannot decrease the
lower elevation angles too much. Going below -10dB is probably not
agood idea. Also, going from ~10 birds in view down to ~5 means that
your PPS jitter just increased by a factor of 5 to 10. 
(source: experiment i've done here some time ago)

Besides, a narrow band jammer trips up most of the commercial receivers
badly (adds a correlation peak where it does not belong).
And for that to be effective you only need to be 5-10dB above the noise
level. Which is pretty easy to achieve, even if you have very directive
antenna (the sidelobes are usually only 10-30dB down from the main lobe)

Fortunately, narrow band jammers are also pretty easy to mask, given
you have enough bits in your ADC.

> As others have noted intermittent jamming is pretty benign to a GPSDO.
> Spoofing, OTOH, can trivially mess up the timing.  It's my view that
> if you need timing for a security critical purpose there isn't really
> any GNSS based solution commercially available to the general public
> right now, the best bet is a local atomic reference with a GPSDO used
> to monitor and initially set it.

There is a reason why Microsemi is building more 5071 these days than
ever before (rumors have it that they are are 3-4 devices per week).

   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, Neal Stephenson

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Re: [time-nuts] NIST

[Attila Kinali]

On Thu, 30 Aug 2018 18:54:17 -0700
Brooke Clarke  wrote:

> I wonder if anyone has tried using a small parabolic dish, like used for Free 
> To Air satellite TV and aimed it at a GPS 
> satellite track or at a WAAS geostationary satellite using a feed antenna 
> with reverse polarization from a normal GPS 
> antenna?

I have somewhere a paper (which i cannot find currently, sorry) that
used a dish trained at one of the EGNOS satellites and used it as the
only source for timing. IIRC the results were promising, but not
spectacular. The problem being that all the ionospheric and tropospheric
effects limited the performance, which also could not be averaged
over several satellites. Hence most people today focus on whole
constelation systems and try to get the best out of that, even under
multipath and jamming.

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, Neal Stephenson

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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

 “Backbone timing” gets done by boxes buried deep in systems. Those systems 
take years
to design. The boxes that go in them similarly take years to get onto the 
market. Once designed
deployment is far from instantaneous. Operators are always pressed by cost 
constraints. Adding
anything beyond the minimums … not going to happen.

The result is that there are no systems out there that use WWVB or WWV other 
than wrist watches
and wall clock like devices. Utilities (cell phones, internet, finance ) run 
with something else. Converting
them to a secondary “something” is a many years sort of thing, even if it is 
technically feasible. 

You can pull a bunch of spare GPS sat’s out of storage and get them in orbit 
*way* quicker than you can 
rebuild every cell tower in the country. In fact, newer designs run their 
timing in a way that a GPS failure 
is not that big a deal. How long it’ll take before that sort of design is 
common in the US…. years and years …

If you are going to come up with a time source at the ~ 10 ns level, that’s not 
going to happen from WWVB
or WWV. They never were good enough to get to that level and it’s not on the 
transmit end. You would need
a very different system. It’s been a long time since any of these services 
(internet, finance, cell )  were in the 
millisecond or even the microsecond range. The modern stuff in all theses areas 
 is  < 100 ns. 

How long would it take to change all this? Well first some random Senior Member 
of the IEEE would 
have to start writing papers about the various issues. Various organizations in 
various countries would 
need to hold meeting after meeting after meeting talking things over. Somebody 
eventually would have
to come up with funds to actually try a few things. Maybe they work in the real 
world / maybe they don’t
work. 

Once you prove you have a system that can do “good enough", you would need laws 
/ regulations passed to
make the “new thing” part of the required designs. You also need funding bills 
to deploy the “source” end 
of things and time to get that up and running. Once it’s running, you then give 
manufacturers some amount of time 
to get it in the field ….. and extensions when that doesn’t happen. Twenty 
years? Thirty years? Maybe longer? 
This stuff does not go very fast. 

Best bet on what the “new thing” would be? Something like IEEE-1588 over fiber. 
It cuts out a bunch of this and 
that in terms of experiments and testing the basic system. We know most of 
*how* to do it already. It’s just a matter 
of a  billions of dollars in tax money to get the gaps filled in and then a few 
tens of billions in tax money to get
the backbone gear in place. Once that’s done you ramp up to the really 
expensive part of the deal ….Is it paid
for by your tax return in April or by a higher price on every cell call / 
transaction you make? … who knows … it’s 
a tax that you are paying either way. 

Bob

> On Aug 30, 2018, at 2:14 PM, Peter Laws via time-nuts 
>  wrote:
> 
> On Thu, Aug 30, 2018 at 12:59 PM Bob kb8tq  wrote:
> 
>> There most certainly was a lot of “stuff” in orbit by that time. If there was
>> a mass die off of satellites, you would not have to look hard to find out 
>> about
>> it.
> 
> Probably not as many as there are 3 decades later, but of course.
> Satellite service (any type of satellite) is much more likely to be
> human-caued.
> 
> But here (and in other fora) the concern is that WWV Must Be
> Maintained in order to save us from being late for coffee if another
> event on the level of the Carrington Event takes out every single GNSS
> spacecraft in orbit.  But I can't find anything on the effect of that
> sort of solar event on satellites.  Almost as if, maybe, satellite
> operators were aware of solar physics and planned for this sort of
> event.
> 
> And I still haven't seen any coherent argument in favor of keeping WWV
> that doesn't involve nostalgia or (perhaps) unfounded fear.
> 
> -- 
> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
> 
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[time-nuts] Possible End of Daylight Savings Time in Europe?

[John Franke]

See: 
https://www.msn.com/en-us/news/world/europe-ticks-closer-to-ending-daylight-saving-time/ar-BBMGU2d?ocid=spartandhp

John  WA4WDL

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[time-nuts] UK: Annual maintenance: 3–21 September 2018

[David J Taylor via time-nuts]

From the NPL:

Annual maintenance: 3–21 September 2018

The annual maintenance shutdown of the MSF service to allow safe maintenance 
of the masts and antennas, including greasing of the stays, will take place 
between 3 and 21 September 2018. The service will be off-air from 08:00 to 
18:00 BST each day, including weekends. If the weather is unsuitable for 
work to be carried out, then the service will not be turned off. If the work 
is completed sooner than 18:00 BST on any day, the service will be restored 
as soon as possible.


 
http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-outages

Question to time-nuts: could you manage with a daytime outage of WWVB for 
over two weeks?  Haven't heard many UK folk complaining during previous 
maintenance periods.


Cheers,
David
--
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 



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[time-nuts] Fwd: Re: law and regulation applying to time.. was Re: OOPS on my wwv legal post

[Dr . Götz Romahn]

 Weitergeleitete Nachricht 
Betreff: Re: [time-nuts] law and regulation applying to time.. was Re: 
OOPS on my wwv legal post

Datum: Fri, 31 Aug 2018 11:25:44 +0200
Von: Dr. Götz Romahn 
An: Dr. David Kirkby 

For German regulations see here:
https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time.html
Götz


Am 31.08.2018 um 00:30 schrieb Dr. David Kirkby:

On Thu, 30 Aug 2018 at 14:03, jimlux  wrote:



There may well be a law in the United States, probably buried in some
enabling or appropriating bill, that says "The Department of Commerce
shall provide national standards for mass, time, voltage, etc."  but
that doesn't say "and all residents of the United States shall use only
the standard provided by the Department of Commerce, and no other"

What about Germany? Notoriously it is "Das Land der Gebote, der
Vorschriften, und der Verbote."  (Commandments, regulations, and
prohibitions)




In the UK there are laws requiring metric for most things - beer being one
obvious exception I can think of, as I had 3 pints today.

https://www.gov.uk/guidance/packaged-goods-weights-and-measures-regulations

That said, it references the "1985 Weights and measures Act"

http://www.legislation.gov.uk/ukpga/1985/72/contents

which refers to "United Kingdom primary standards and authorised copies of
the primary standards."

The United Kingdom primary standards shall be—

(a)in the case of the yard, the bar described in Part I of Schedule 2 to
this Act;

(b)in the case of the pound, the cylinder described in Part II of that
Schedule;

(c)in the case of the metre, the bar described in Part III of that Schedule;

(d)in the case of the kilogram, the cylinder described in Part IV of that
Schedule.

Then going to the metre definition, it talks of an X shaped bar

http://www.legislation.gov.uk/ukpga/1985/72/schedule/2

I believe that is almost certainly the one held at NPL, and was on display
at the recent "NPL Open House". However, it makes no reference to NPL
directly.

There was a case of a butcher not too far from me who refused to sell meat
in kg.

http://news.bbc.co.uk/1/hi/uk/629763.stm

I believe he died before going to prison, but he was quite adamant he would
not sell in kg. It would have been interesting if he priced his meat at £12
/ 0.45454545454545454545454545454545454545454545454545454545454545454 kg,
which would be £12/pound.

When it comes to time (the subject of this list), I'm not sure where the UK
stands legally. I will ask on the newgroup uk.legal.moderated

https://groups.google.com/forum/#!forum/uk.legal.moderated

which is visited by solicitors, students of law, and people wanting legal
advice.

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
https://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
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--
Götz Romahn

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Re: [time-nuts] WWVB Signal Generator

[Wayne Holder]

> Wayne very good progress. You can actually feed the loop coild that exists
> with the cap it should resonate.
> Thats my plan at least.

Thanks, Paul.  Actually, after running a few more tests, the BALDR seems to
now set quite reliably with the wire just wrapped around the ferrite rod as
long as the clock is with 2 inches of the ferrite rod.  I'm using the WWVB
receiver module in another experiment, so I don't want to risk damaging the
module by applying a 5 volt PVM signal to the coil.  But, I have a another
WWVB receiver module on order so, once it arrives, I'll try out your
suggestion.  I've also ordered some ferrite rods in order try my hand at
rolling a 60 kHz antenna from scratch, so that will be another adventure.

Wayne


On Thu, Aug 30, 2018 at 8:04 PM paul swed  wrote:

> Wayne very good progress. You can actually feed the loop coild that exists
> with the cap it should resonate.
> Thats my plan at least.
> Regards
> Paul
> WB8TSL
>
> On Thu, Aug 30, 2018 at 9:44 PM, Wayne Holder 
> wrote:
>
> > I've had some luck improving things with my ATTiny85-based WWVB Simulator
> > design by replacing the crappy, 8 MHz internal oscillator with an 8 MHz
> > crystal and removing the tweaked timer values I had previously used.  In
> > addition, based on a suggestion from Paul Swed, I tried looping the
> antenna
> > wire a few times around the ferrite rod of a WWVB receiver module I
> > happened to have lying around and this also greatly improved things (see
> > photo on web page at
> > https://sites.google.com/site/wayneholder/controlling-time).  In fact,
> > with
> > the ferrite rod in place, the BALDR clock now syncs even when completely
> > disconnected from being grounded to the ATTiny85 and the scope.
> >
> > I've updated my web page, and the source code at the bottom of the page,
> > accordingly.  BTW, the SYNC output is now moved to pin 7 and the PPS
> output
> > is currently disabled in the code. In addition, I've added some
> additional
> > info on my web page about how to compile and download the program to an
> > ATTiny85 using ATTinyCore by Spence Konde.
> >
> > I've ordered a 15.36 MHz crystal to try, as that should let the ATTiny85
> > generate a true, 60,000 Hz output but, so far, the 8 MHz crystal has
> helped
> > improve things quite a bit.  In addition, I plan to do more tests on
> > different types of antennas in order to see if I can make things even
> more
> > reliable and stable.
> >
> > I still plan on reworking the code so it can also run on a 328-based
> > Arduino board but, currently, the Arduino IDE has no easy way to work
> with
> > boards that don't use a standard, 16 MHz crystal, as this frequency is
> used
> > by the serial port and, in turn, by the boot loader, so altering it can
> > break the ability to upload code.  This has actually caused some issues
> for
> > some of my other projects, so I'm investigating how this issue might be
> > handled.
> >
> > Also, if anyone is interested in trying out other modulation schemes, I
> can
> > easily add a compile option t the code that will let it output a binary
> > low/high modulation signal instead of the PWM signal.
> >
> > Wayne
> >
> > On Thu, Aug 30, 2018 at 8:53 AM paul swed  wrote:
> >
> > > Wayne as I work through the chronverter I do know the good phase
> tracking
> > > clocks really demand on frequency behavior. As I measured its +/- .6 Hz
> > at
> > > 60 KHz. I believe the cheapy wall clocks are a bit wider, but not sure
> as
> > > they are hard to actually measure. They do use a small tuning fork
> > crystal
> > > and from experience these are sharp. When I experimented with them they
> > > were maybe 5 Hz. Indeed the Chinese website had 25 X 60 KHz crystals
> for
> > > maybe $2.
> > > With respect to the antenna. My thinking is a loopstick resonated on 60
> > KHz
> > > and most likely driving it push pull or single ended. Thats 1
> transistor
> > if
> > > single ended as common collector if I had to guess. The reason is the
> > > micros put out a fair level of signal so its a case of upping current
> > into
> > > the antenna. But it really will be a bit of experimenting.
> > > I did look at your code and that was so nice it opened up straight into
> > the
> > > arduino IDE.
> > > Regards
> > > Paul
> > > WB8TSL
> > >
> > > On Thu, Aug 30, 2018 at 5:12 AM, Wayne Holder 
> > > wrote:
> > >
> > > > For anyone trying out my ATTiny85 code, I've done some additional
> tests
> > > and
> > > > find that placement of the antenna near the clock is very finicky
> and,
> > so
> > > > far, the only way to get a reliable decode of the time in the clock
> is
> > by
> > > > using a scope to monitor the demodulated output and then moving the
> > > antenna
> > > > around until the demodulated signal lines up cleanly with modulated
> > > carrier
> > > > and there are no intra bit glitches.  This can take a bit of
> patience,
> > so
> > > > clearly a better solution needs to be found.  I've found that any
> type
> > of
> > > > glitch in