Best practices question

[Patrick]

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:
>   https://www.febo.com/time-freq/wwvb/vlf.html
> 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.

[1]https://www.febo.com/jra.html
[2]https://i.pinimg.com/originals/67/1e/47/671e47898d707b989d98929c9a35e45a.png

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?


Patrick