[time-nuts] Accuracy/drift of Garmin GPS 16 HVS 1 PPS output under invalid fix conditions...

[David J Taylor]

Hi All,

Just a basic question for an application with low accuracy
requirements.  I only need an accuracy of +/- 1 ms on the 1 PPS signal.

Does anyone have any data on the behaviour of a Garmin GPS 16 HVS (or be
able to point me in the right direction to find such data) w.r.t. the 1
PPS output when a valid fix is not available.

I need this to determine whether the 1 PPS hold-over accuracy is
sufficient to maintain the 1 PPS within +/- 1 ms of GPS time during a
loss of GPS lock of, say, 15 minutes.

I know that different manufacturers might handle the hold-over
differently - so I need some experience of others with Garmins.

The only information I can find about Garmins is that the 1 PPS holds
within the +/- 1 us specification for up to 4 seconds of invalid fix
conditions.

Cheers

Steve Olney

HawkRAO

http://hawkrao.joataman.net/pulsar/daily_obs/index.html
=============================================

Steve,

Not a lot to add, but I have also seen Garmin GPS devices where the PPS 
disappears almost immediately.

This device claims "Hold over on loss of GPS signal (is) typically 2ms in 24 
hours", so well within you requirements.  I don't know whether that applies 
just to its NTP serving function or to the PPS output as well.  Worth 
asking....

  http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=272

Cheers,
David
-- 
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk
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