Best practices question

Patrick 201905-ntpsec at
Fri Jun 28 02:06:59 UTC 2019

On 2019-06-27 13:59, Hal Murray wrote:
> >> I thought the ground wave was supposed to be stable.
> > Except the ground wave may be interfered with.
> Off list, Chris Caudle sent this URL which has a good graph:
> It shows a roughly 20 microseconds shift from day to night.

Febo is in Atlanta,[1] so the mountains in between[2] him and Ft Collins means
that his path has an ionosphere bounce.


For receivers on an indirect path, the periodic shifts are predictable
and can be censored -- i.e. everyday outages requiring holdover.

Given a scenario where all GPS satellites are offline, and since eLORAN
has not been rolled out yet, is WWVB/DCF77/MSF/JJY is the next best
alternative that can be built for less than 500 USD?

Or is there a same-budget holdover strategy that will be better for the
the time required (estimate 3 months) to launch replacement satellites?


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