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    Re: Choice of timepiece
    From: Lu Abel
    Date: 2009 Nov 13, 17:04 -0800

    GPS time displays can be "off" for one of two reasons:
    1.  The actual time used by the GPS system is not compensated for 
    leap-seconds.  Every GPS receiver built in the last 15 or 20 years knows 
    the difference and can be set to display correct UTC.   In fact, the 
    default settings on GPS receivers are for UTC and not GPS time.   But 
    you can change that, perhaps inadvertently.
    2.  The time it takes the receiver to display the time (!).   While this 
    was significant in older GPS receivers, I've personally not heard a 
    complaint by someone owning a more recent receiver.   Regardless, 
    though, this should be a consistent delay and we can simply view it as 
    watch error and compensate for it as any good navigator ought.   I find 
    references to the Trimble Transpak dating back at least to 1993, so it's 
    an antique and it's not fair to define the performance of current 
    receivers by comparing them to the Transpak.
    Let's not forget that that old tried and true standby, radio time 
    broadcasts, can also be off.  If one is half way around the world and 
    listening to one of the SW time broadcasts you suggest, it takes almost 
    a full second for the broadcast tick to reach the receiver!
    douglas.denny{at}btopenworld.com wrote:
    >  "...Timepieces are one of the ways CN has changed
    > in the age of GPS.  You can always check your watch against the GPS
    > time..." 
    > =========
    > No you cannot.  This has been aired here before I believe.
    > Unfortunately,  the designers of GPS equipments do not necessarily 
    incorporate correct UTC time in the _displayed_ time.
    > The display time can be several seconds 'out' from the correct UTC.
    > I have no idea why. It is a gross and stupid and entirely avoidable fault in 
    my opinion and an indictment of poor and/or cheap design, and could be 
    entirely eliminated very simply with very little effort with good design.  In 
    fact it must be a simple software design fault as the hardware has internal 
    one second pulses available which are incredibly accurate.
    > The fact that the rising edge of the one second pulses available are 
    accurate to close to atomic standard time is plain silly when the display can 
    be several seconds wrong.
    > My Trimble Tanspak display update is always one second behind true UTC for 
    the update time - at least it is only the next second update 'out' - not 
    several seconds.
    > The only way to be sure is to take a shortwave receiver with you and use 
    standard time signals or to be sure of your GPS if it is consistent and 
    correct in the display of time having checked it against a standard.
    > I have a small Sony ICF-7600 receiver (7" x5" inches in size) which I have 
    used for 'mobile' use for about 20 years which is in effect a miniature 
    communications receiver with BFO for CW reception and you can use an external 
    antenna if wanted, though the small telescopic whip is OK mostly.
    > You can obtain time signals (one second or tenth second pips) in Europe 
    available 24 hours on 4.9996 MHz and 9.9996 MHz (RUM from Russia); and there 
    is WWV in America on 5 and 10 MHz.
    > Spoken Wx reports too from Shannon for worldwide airports and there are 
    other useful stations too worldwide.
    > Connect your laptop and with the suitable decoding software to the 
    communications receiver and there are 'proper' Weatherfax stations available 
    for weather maps (surface isobar charts  and  progosis charts too) broadcast 
    24 Hrs.  I regularly use the Northwood on 4610 KHz here in the UK.
    > Douglas Denny.
    > Chichester.  England.
    > =======================
    > Original Posting:-
    > David,
    > I too navigate with a Timex.  Mine is a Timex "Indiglo" which cost
    > about $15 -- if I remember right.  It consistently looses about one
    > second in four months.  Timepieces are one of the ways CN has changed
    > in the age of GPS.  You can always check your watch against the GPS
    > time.  And there is no need for a mate to write down the sight time at
    > your call of "mark".  You can quickly look at the seconds digits
    > without any appreciable loss of time.  No need to keep a chronometer
    > log and make watch corrections.
    > Welcome to CN in the GPS age,
    > JK
    > >
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