[time-nuts] Best Chance GPS module
mlewis000 at rogers.com
Wed Nov 30 16:11:05 EST 2016
(resending as I tried posting in html...)
I'm a novice at time issues. I've been gathering info and I think I'm
ready to start asking questions.
I'm after a time solution for my personal computer. It looks like I need:
* a standalone box to be my own local personal NTP server (so the
variable processing load on my main box can no longer affect host
polling software timestamps...)
* run standard NTP Client & Host software on that box
* discipline it with PPS from GPS, using an active antenna
* use NTP to obtain the NTP time from this local personal NTP server
* I don't know if I need two additional boxes: one for the NTP host
and another for receiving the GPS PPS signal, like a Pi in kernal mode.
* I'm in a semi-basement apartment.
* Building faces due South.
* Building is 1960's brick & concrete, steel trusses & sheets in
place from the concrete floor pours.
* Windows from 14" to 38" from the ground. My antenna has to be
* Window frame is plastic retrofit over wood Pearson-sliders.
* There is a bank of buildings due south of me that leaves me with
clearance elevations between 6 and 12 degrees. I'm at 45.42 North.
* Due South within what open sky I have, are two heights of
electrical wires, around 35 feet out from the building at the edge of
the parking lot.
I'm expecting multipath from: those buildings, my building and I assume
the wires and possibly the cars?
Between the multipath and a less than full view of the sky, I believe
I'm needing a GPS module:
* that is sensitive,
* good multipath handling,
* GPS & GLONASS, to get as many sats possible out of the sky-view I have.
Due to my location difficulties, considering newer more sensitive GPS
modules seems to make sense, even if they're not timing modules. I was
tempted by a Qualtec L86 with -148|-165 dBm or a SkyTraq Venus838LPx-T.
Then a ublox Max-M8Q with -165|-167 dBm & its stationary mode. But then
I discovered I can get a ublox NEO-M8T with -165|-167 dBm sensitivity,
its multipath handling and concurrent reception of GPS/QZSS, GLONASS,
BeiDou & Galileo.
A ublox NEO-M8T with an active timing antenna (GPS | GLONASS ?) seems to
be my best chance of being successful at my location.
* Is there a more suitable GPS module than the ublox NEO-M8T for my
* Can anyone recommend an affordable suitable antenna for GPS & GLONASS?
* One box or two, for running a local NTP host and receiving the PPS
from a GPS module?
* Is there a better solution for a micro board than a Rasp Pi with
its USB controlled Ethernet, or the BBB with it's RF issues?
* What am I not considering that could end up biting me?
More information about the time-nuts