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POTENZIALE PROBLEMA CON IL GPS IL 6 APRILE

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  • POTENZIALE PROBLEMA CON IL GPS IL 6 APRILE

    Ciao a tutti,

    non so a quanti possa interessare questa notizia ma la ritengo interessante per chi utilizza il GPS. Potrebbe essere un problema simile all'atteso del millennium.
    Da quello che ho capito, qualche apparato GPS utilizzato potrebbe cambiare data ma fornire l'impulso di 1pps corretto

    Mi dispiace che le informazioni siano tutte in inglese, le ho ricevute oggi dal gruppo tecnico della rsgb. Spero qualche volontario metta in luce, in italiano, il probabile problema e che cosa potrebbe succedere.

    73

    Gian
    I7SWX

    2a.
    Possible GPS problem 6th April
    From: Peter Martinez
    Date: Sun, 24 Feb 2019 11:00:00 CET

    My attention has been drawn to the appended post by Mark GM4ISM. I think my own GPS (Trimble Palisade) will be OK. It already gives me the wrong date - probably because it missed the last week-number rollover in August 1999. After April 6th it might stay 19 years ago or it might jump to 39 years ago, but the time and the PPS should be OK.

    73
    Peter G3PLX

    -------- Forwarded Message --------
    Subject: [UKMicrowaves] GPS Frequency standards.. Week Zero alert.
    Date: Thu, 7 Feb 2019 18:39:05 -0000
    From: Mark GM4ISM via Groups.Io <gm4ism=blueyonder.co.uk@groups.io>
    Reply-To: UKMicrowaves@groups.io
    To: UKMicrowaves@groups.io



    For those of us reliant on GPS based frequency standards and location
    systems, there is an upcoming event that may upset some GPS engines.

    GPS week numbers only go up to 1024 and we hit another 'week zero' event
    on 6th April this year.

    This can and does cause some older GPS engines to become rather upset.
    Some completely loose lock, some may still produce 1PPS etc but output
    the wrong date and time
    Many of these recover at week 1 but that is not guaranteed.

    Some testing has been done by a colleague on a number of GPS based
    systems using a locally generated GPS signal set that simulates the week
    zero signals.
    A number of older GPS engines have failed this test and the frequency
    standards associated with them have been shown to go into holdover and
    start to drift....
    Amongst the ones likely to fall over are the Rockwell chipset widely
    used by amateurs. The exact model with 10KHz (Jupiter) out has not been
    confirmed but pretty much all of the related models, used in a number of
    GPS disciplined oscillators, fell over.
    The Jupiter in my old RUH system already needs a poke of serial data at
    start-up, I believe to correct a previous timestamp rollover. I guess it
    may need a different one soon.
    I am aware that if all else fails, UBlox GPS engines have been
    successfully used in the RUH design standard in place of the Jupiter, as
    some Ublox engines can be programmed to output the required 10KHz
    instead of 1PPS
    All (slightly older ) UBlox modules that have been tested were
    unaffected so it is likely that newer ones will be OK too,

    Some older Rapco GPS standards fail the Week Zero test which makes them
    think they are the best part of twenty years younger. Their recovery
    into week 1 is not certain.

    I am aware that at least one model of these has an internal firmware
    week counter which will rollover in July if I recall, further
    complicating matters
    I also have one of these and its useful life is now in question.

    The Trimble Palisades out there are an unknown quantity.
    I will try to get one tested. I use one of these with a VE2ZAZ system
    and so does GB3CSB



    Recovery in week 1 has not been tested in my world, a full week in
    holdover is not acceptable so units are being replaced.


    So the upshot is that for the duration of week 0, your GPS freq
    standard, if based round an older GPS engine, may fail to lock and
    provide an accurate 10MHz
    I have a Rubidium standalone, which I fear I may need because none of my
    references are modern.


    You may see people flogging off some professional GPS frequency
    standards. Some may be real bargains if there is a 'fix', other may
    become simply a source of a reasonable 10MHz OCXO Caveat emptor!


    Happy Binary Birthday GPS!

    Mark GM4ISM
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    2b.
    Re: Possible GPS problem 6th April
    From: David Barber
    Date: Sun, 24 Feb 2019 11:44:33 CET

    Just out of curiosity I wonder why this / these issues are out there?

    Did the clever people who designed the hardware and wrote the firmware for
    these GPS modules 'forget' this would happen? Was there a cost saving in
    doing it this way?

    Or were these modules never expected to be in service for a period beyond
    which the issue would be encountered?

    David Barber
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    2c.
    Re: Possible GPS problem 6th April
    From: Peter Martinez
    Date: Sun, 24 Feb 2019 12:24:56 CET

    David said:

    Did the clever people who designed the hardware and wrote the firmware for
    these GPS modules 'forget' this would happen?

    I am guessing that this problem is just poorly-written software. The Millenium Bug was a similar problem, where programmers chose to record years with only the last two digits (so it should have been called the Century Bug!) so at year 2000 these programs registered the year as 1900. In this case the GPS satellites only have 10 bits to count the passing weeks and then return to zero, which it will do midnight 6/7th April. GPS receiver designers should have been able to predict this and avoid it, but evidently some of them will malfunction and some may never work properly thereafter.

    73
    Peter G3PLX

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    2d.
    Re: Possible GPS problem 6th April
    From: Dave Sergeant G3YMC
    Date: Sun, 24 Feb 2019 13:27:30 CET

    There seems to be quite a lot of confusion on this matter, and even
    with far newer satnaves. Tom Tom have a page about it on their website
    with a box to type your satnav serial number to check. My Start 20
    comes up as needing a firmware update but when I check it online there
    is none available. It seems it was patched in a software update early
    last year which it had installed already during the normal updates.
    Together with as reported on the radio last week them sending emails to
    customers with a link to click that looked just like a spam. I imagine
    most current satnavs will continue to work just fine, but clearly we as
    amateurs who use them in different modes may find otherwise.

    73 Dave G3YMC

    On 24 Feb 2019 at 9:53, Peter Martinez via Groups.Io wrote:

    My attention has been drawn to the appended post by Mark GM4ISM. I
    think my own GPS (Trimble Palisade) will be OK. It already gives me the
    wrong date - probably because it missed the last week-number rollover in
    August 1999. After April 6th it might stay 19 years ago or it might jump
    to 39 years ago, but the time and the PPS should be OK.


    http://davesergeant.com

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    2e.
    Re: Possible GPS problem 6th April
    From: Neil Smith G4DBN
    Date: Sun, 24 Feb 2019 14:20:53 CET

    Tim N3QE has a Z3801 which is going through it's second rollover and will be into its third 1024-week epoch.

    For the technical detail about rollover, search the Time-nuts forum for "Rollover" (it is indexed on google). Loads of intricate stuff on there about the issues around rollovers.

    Good history at http://www.leapsecond.com/notes/gpswnro.htm

    whenre Joe Gwinn discusses (amongst other things) the use of the drifting offset between GPS time and UTC as an identifier for which 1024-week GPOS epoch you are in.

    https://www.febo.com/pipermail/time-...ne/067840.html

    https://lists.febo.com/mailman/listi...lists.febo.com

    Beware of getting assimilated into the world of time-nuttery, you'll start losing sleep because your 1Hz offset at 10GHz is an appalling lapse of precision.

    Neil G4DBN

    PS, check out volt-nuts as well. As if you don't have enough to worry about with time and frequency precision
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    2f.
    Re: Possible GPS problem 6th April
    From: mike
    Date: Sun, 24 Feb 2019 19:43:55 CET

    Almost certainly the latter.
    ISTR the Y2K bug got everyone up in a lather too.
    Lets wait and see what your GPS engine does..As for mine, I really dont care
    so long as the 1pps stays accurate...
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    3a.
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