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    Re: Radio Clock or Internet GMT - which should I believe?
    From: Lu Abel
    Date: 2012 Mar 3, 16:46 -0800
    Paul:

    If I were afloat, a shortwave receiver would certainly be a mandatory piece of equipment.   But don't forget that GPS keeps incredibly accurate time and presents a viable backup source of time checks.   Frank pointed out that while GPS receivers internally know what time it is to the nanosecond, some GPS's have exhibited significant delays in displaying that time.   I believe this occurred only with much older receivers and not with GPS's built within, say, the last five years.   But it behooves any navigator to understand if there is any error or delay in GPS time display.

    There are many of us who are shore-bound and practice navigation as an avocation and not a profession.  Most of us have access to a high-speed Internet connection and I believe that (for users in the US, at least) time.gov offers an excellent alternative to the exigencies of getting a good SW radio signal.

    I presume most of us already have computers (else how are you reading this email?) so there is NO cost associated with using time.gov.

    I have an excellent radio controlled clock that the local electronics superstore was selling several years ago for under $10.   But I have also had experience with a friend who bought, by mail-order, a beautiful wall radio-clock.   It hardly works (will only synchronize at night when radio propagation is better).  Chinese goods and probably has a really crummy receiver.  

    So I wouldn't short-change any of these alternatives (GPS, time.gov, radio clocks).   But as with any technology, the prudent navigator doesn't blindly accept the numbers but understands whence they come and double-checks them.

    Lu


    From: Paul Hirose <cfuhb-acdgw---.net>
    To: NavList@fer3.com
    Sent: Saturday, March 3, 2012 2:50 PM
    Subject: [NavList] Re: Radio Clock or Internet GMT - which should I believe?

    Lu Abel wrote:
    > WWV is indeed the "gold standard" but not always available reliably and cheaply, so alternatives such as time.gov or atomic clocks are reasonable parts of a navigator's arsenal.

    But "not always available reliably and cheaply" would apply even more to Internet time or a radio controlled clock, wouldn't it? I think a navigator dependent on those time standards, without a shortwave receiver, is living dangerously. If they disagree, how do you know which one is wrong?

    Shortwave reception isn't alway there, but if you can hear a time station, you can trust it. There are no doubts about delay in the network or within the device, e.g., the time display on a GPS receiver.

    (In some applications the radio propagation time does matter, though. At a place where I used to work, there was a rubidium clock which could be checked or synchonized to ticks from a WWV receiver. The equipment included a set of thumbwheels to input the distance to the station.)

    For years I've made monthly rate checks on two of my clocks. For that I rely on WWV via cell phone. The audio is 1/4 second late, a delay I ignore because it's so consistent. Without a shortwave receiver I wouldn't have that confidence.

    There are several time broadcast stations scattered around the world:

    http://search.yahoo.com/search?p=standard+time+frequency+stations

    My receiver is an old Sony 2010 from the 1980s. Portables from China nowadays do a decent job for well under $100 and would be good time standards. A couple retailers who have been in business many years:

    http://www.universal-radio.com/
    http://www.grove-ent.com/

    Some cheap receivers sold only through eBay or other outlets are said to perform well for the money, if you don't mind Chinese instructions (or none at all) and no warranty or support.

    -- I filter out messages with attachments or HTML.





       
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