On 2012-02-24, David J Taylor <david-tay...@blueyonder.co.uk.invalid> wrote: > "unruh" <un...@invalid.ca> wrote in message > news:cmQ1r.3572$py5.2...@newsfe09.iad... > [] >> The graphs of the signal strengths at the edges of these dropouts is in >> ftp://theory.physics.ubc.ca/outgoing/drop{out,in}.pdf > > Could not access this page in Firefox.
These pages. dropout.pdf and dropin.pdf sorry if my use of the bash syntax confused you. > > [] >> Is this a flaw in the Sure unit (NOte that the sure unit drops its PPS >> signal as soon as it does not a fix. Some units-- Garmin?-- keep sending >> out PPS based on the freerunning onboard clock for quite a while, as I >> understand it. >> Teh Sure does not, which may be an advantage or a disadvantage. >> (ntpd/chrony grab one of the other servers which produces >> discontinuities in time when the pps comes back) >> >> Is it evidence of some outside noise source (jamming?) , microwave tower >> emission? > > That's certainly a possibility. I would try to locate the antenna so that > it has a clear view of at least half the sky, preferably towards the > south. You may also notice seasonal effects with foliage blocking the > signal more in spring and summer. It has. I plotted the location of the satellites in the sky using S/N bands. I can see the whole sky (ie sattelites are tracked across the whole sky-- except for a hole in the northern sky where I guess the satellites never go as viewed from Vancouver.) There are some trees to the east, and they seem to reduce the S/N by about 10dB but they are still visible and tracked even through the trees. (Cedars) > > Mine have a moderate view of the sky, being located indoors, but on the > top floor of a domestic residence. Both pucks are stuck (magnetically) on > top of a PC, which does form a ground plane, but may also be a source of > electrical noise! I haven't monitored as you have, but I suspect I see > the effects of a drop-out perhaps once a fortnight. Mine are stuck to the iron flashing around the top of the building-- about 1/2 a meter wide. But that flashing is not attached to any microwave noisy source AFAIK. > > Cheers, > David > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
