[time-nuts] Timing Distribution in Mountainous Terrain

WB6BNQ wb6bnq at cox.net
Sat Sep 11 00:46:37 UTC 2010


Hal,

The LORAN frequency was picked to have predominately ground wave acquisition over
the less preferred skywave.  The only signal worth considering from Fort Collins
is the WWVB signal which is at 60 KHz.

For Ralph's application in Colorado, the WWVB signal would probably do it.
Particularly considering the short distance between the sites and Fort Collins.

LORAN and WWVB are about the same as far as stability goes at the actual
transmitter site with WWVB having a slight edge.  The value is 1x-E11 or better.
For Ralph, the WWVB would be more stable due to his site proximity to the
transmitter over any LORAN signal (when working) which is much further away.

Bill....WB6BNQ


Hal Murray wrote:

> ralph at ralphsmith.org said:
> > There are probably several fatal flaws with this approach. In particular,
> > the following are required:
> > 1) Ability to maintain constant lock to WWV
> > 2) Common-mode error. Will the propagation from WWV be similar
> > enough for all stations to it be a practical common reference.
> > 3) Adequate resolution. Even if, for some reason 1 and 2 are possible,
> > would the result be good enough to use.
>
> My quick guess is that WWV would be worse than LORAN since LORAN got to pick
> the frequency that would work best.
>
> If you want more info, you probably need to contact a radio propagation
> wizard.  Unless you are very close, the signal will be bouncing off the
> ionosphere and that isn't stable.  There are big changes from day to night,
> and I think you can measure the tiny changes during the day if you have a
> good clock at the receiver.
>
> Didn't one of the recent FMT discussions mention something like this?  I
> think they were measuring a frequency shift which would translate into
> velocity of the layer.
>
> Dave Mills has drivers for NTP that decode WWV/H signals from a short wave
> radio going into a PC audio chip.
>   http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver36.html
> In general, he's getting sub ms rather than few ns.
>
> --
> These are my opinions, not necessarily my employer's.  I hate spam.
>
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