[ntp:questions] using both a PPS source and a HBG (dcf-77-like) timesource?
David L. Mills
mills at udel.edu
Mon Jan 14 14:28:18 UTC 2008
AS little bit of digging in th NIST monograph of 1965 shows the change
in carrier phase lag at 60 kHz varies abouit one cycle or 17
microseconds over the day and night. This is for a 2460 km path between
Boulder and Ottawa where the ray angle incidence is rather small.
Another reference shows the ionospheric reflection height varies 73-87
km over the day and night, which for vertical incidence results in about
47 microseconds variation. Make the ray propagation delay 3.3
microseconds per km.
Hal Murray wrote:
>> The radio receiver will be late by of the
>>order of millisec, while the gps will be "on time" to microseconds.
>>Of course you may not care, but someone who has two onboard time sources
>>would care, I would think.
> The radio propagation delay can be "fudged" out.
> How stable is the radio delay? I remember discussions about night vs
> day, but I think that was for long distances, bouncing off the
> ionosphere which changed height at night. I'd expect it to be
> pretty stable if you are close to the transmitter - ground wave.
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