[ntp:questions] garmin 18x and linux
Miguel Gonçalves
mail at miguelgoncalves.com
Wed Sep 7 00:03:31 UTC 2011
On 6 September 2011 23:02, Chris Albertson <albertson.chris at gmail.com>wrote:
> > Why don't the manufacturers provide the PPS signal to the serial port
> > themselves? Is it meant to be NMEA only?
>
> If cost is an issue there are even lower priced options then the one
> from Sure Electronics. Older Moterola UT+ receivers sell for $18.
> These actually have better specs and the signals are all run out to a
> 10-pin header, no soldering.
>
I second this. I am looking at a Motorola Oncore UT+ unit I got on ebay for
about 10 USD. I believe the antenna cost me 7 USD. :-)
A quick trip to the local electronics shop and with a bit of soldering I
have a board that gets the power from USB and returns the GPS signals to
NTP. Oncore is connected to this board by a flat 10 wire cable. Quite neat!
:-)
The performance is quite impressive:
oncore# uptime; ntpq -p; ntpdc -c kerninfo
12:02AM up 2:07, 1 user, load averages: 0.00, 0.00, 0.00
remote refid st t when poll reach delay offset
jitter
==============================================================================
oGPS_ONCORE(0) .GPS. 0 l 7 16 377 0.000 -0.001
0.001
canon.inria.fr .GPSi. 1 u 34 64 377 49.054 0.621
0.383
ptbtime1.ptb.de .PTB. 1 u 36 64 377 66.475 0.864
0.316
ntp.ien.it .CTD. 1 u 6 64 377 52.064 0.452
0.263
ntp02.oal.ul.pt 194.117.9.138 2 u 27 64 377 9.486 0.565
0.453
ntp04.oal.ul.pt 194.117.9.138 2 u 34 64 377 10.109 -0.831
0.235
Router7.Lisboa. 193.136.250.246 2 u 27 64 377 8.181 0.508
0.258
Router15.Porto. 193.136.250.246 2 u 13 64 377 12.538 0.528
0.129
pll offset: -8.37e-07 s
pll frequency: -32.057 ppm
maximum error: 0.004234 s
estimated error: 1e-06 s
status: 2107 pll ppsfreq ppstime ppssignal nano
pll time constant: 4
precision: 1e-09 s
frequency tolerance: 496 ppm
pps frequency: -32.057 ppm
pps stability: 0.016 ppm
pps jitter: 1.811e-06 s
calibration interval: 256 s
calibration cycles: 50
jitter exceeded: 5
stability exceeded: 0
calibration errors: 3
I've tried Garmin 18 LVC and Sure. Not want to start a war here but for the
specifications and price Oncore beats both. :-)
Just my 2c.
Cheers,
Miguel
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