Hi Ok, local RF interference sounds like a significant part of the problem. I would suggest that swapping antennas might make sense. Not all “super interference rejecting” antennas are created equal.
Bob > On Nov 1, 2017, at 9:55 AM, MLewis <mlewis...@rogers.com> wrote: > > I wish. > > It's using GLO and GPS now, yet gets reception dropouts. > That's why I'm hoping to eventually get the firmware update that will add GAL > to the mix. > > I had anticipated reception issues, which is why I went with the M8T for its > sensitivity, multi-constellation and it's a timing module so a good PPS on a > single sat - only to get surprised that my version didn't have GAL enabled. > But I didn't envision reception would be so bad that not having GAL would be > material. > > I'm also too close to that tall building that is reflecting the sats over the > Bering Strait at me. It's a military computer site, which I thought would be > pretty tight on stray RF, but it has antennas. I asked a friend who works > there about my GPS issues and if RF from the site may be influencing things. > He hesitated, then said "'Yes'. That's all I can say." > For first power up I had obtained an active antenna for multi-constellation > and a pre-filter that "provides protection from near frequency or strong > harmonic interfering signals." > > As it's just for NTP accuracy, I may be better off letting all the multipath > through than getting dropouts. I'm starting to think that part of my problem > is that I know the GPS is capable of getting better than I need, so instead > of working to get what I need, I want what it should be capable of. > > But I feel a better solution is a reliable holdover capability, which I > should have anyway for failsafe. So perhaps the reception dropouts are a way > to make me address holdover properly rather than limp in and get surprised > later. > > Hence adding a 'precision' RTC to the Pi. > > Michael > > On 01/11/2017 8:45 AM, Bob kb8tq wrote: >> Hi >> >> For NTP levels of accuracy Glonas is quite fine. Combining that with GPS >> should >> get you a pretty good “time source” even under your extreme conditions. >> >> Bob >>> On Oct 31, 2017, at 11:14 PM, MLewis <mlewis...@rogers.com> wrote: >>> >>> I'm stuck with a near ground level antenna site (~16" above grade?), with >>> half a sky view (thankfully to the SSE), less some low blocking buildings >>> with regular mutlipath, plus multipath bouncing off a taller building to >>> the SE that bounces sats from the NW at me from low over the Bering Strait. >>> The building I'm in is concrete with flat steel under each floor from the >>> construction method. As I write this I'm down to two green sats in LH. >>> >>> A number of times a day, it will drop to one sat, and there's a few >>> dropouts a day where it goes to none of sufficient signal. How many times >>> and for how long varies by the day. It's worse when it's wet out, which it >>> is right now. If I lower the signal strength threshold, then I end up with >>> tons of multipath signals. >>> >>> If I can ever get a bios update to my NEO-M8T, then I'll have GAL in the >>> mix and should experience fewer dropouts, potentially none. >>> >>> An RTC that +/- 3 PPM over 24 hours would be great for holdovers of one to >>> 20 minutes. >>> >>> While I wrote this, LH was typically showing two or three green sats, once >>> up to five and once down to one. And I just hit a dropout... for a minute >>> and a half; the one remaining green sat went behind the corner of the >>> building's entrance canopy, then back out. >>> >>> >>> On 31/10/2017 10:30 PM, Bob kb8tq wrote: >>>> Hi >>>> >>>> Under what conditions would you expect to loose GPS? I seem to be able to >>>> do just fine sitting in an armchair here in the family room. That’s hardly >>>> a >>>> fancy setup. >>>> >>>> Bob >>>> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
