[time-nuts] Ublox M8N - have I a XO or TCXO ?
Kiwi Geoff
geoff36 at gmail.com
Tue Dec 20 18:08:46 EST 2016
Hello All - and Seasons Greetings,
One of the advantages of the recent hobby drone phenomena - it has
brought to the market a lot of low cost GNSS modules that are
lightweight for drone flight control systems. Those of us with other
hobbies, like "Time Nuts" and RTK - these low cost modules can be a
little goldmine for cost effective toys.
However the dark side is that some vendors are re-badging lower cost
modules, printing their own labels and marking as "Ublox M8N" for
example.
I recently bought two M8N modules, and wondered are they genuine - do
they actually have a TCXO (as they should do) or have I a re-badged
plain M8030 etc ?
A check with "u-center" and looking at UBX-MON-VER shows the correct
info, but what about the oscillator - is it a TCXO , good enough to do
RTK with ?
My other new present from Santa ( in the guise of Mark and John) is LH
5 - wow what a wonderful piece of engineering ! - thank you so much,
it has soaked up many a pleasurable hour !
Looking at the ADEV ability of LH5, I wondered if I could use LH to
answer the TCXO question of "my" M8N devices.
I did an overnight run and (hopefully) attached a screen shot, and
have the ADEV results at the end of this message.
While "I think" the graph and data is impressive, I'm not sure
"exactly" what I'm looking at, is the M8N running a "paper clock" and
so it's like "Man with ONE watch knows the exact time" scenario ?
The Ublox M8N was running outside (with a Max-Min thermometer saying
overnight it was 12 - 18 degrees Centigrade), on the graph you can see
the effect of Sunrise on the module, but I'm surprised how little the
clock changed.
Can anyone comment on the following data, and whether they think the
oscillator in "my" M8N is a XO or a TCXO ?
>From the attached screen shot, you can see the hole in reception over
the South Pole (yes a Southern Hemisphere Time Nut) - but for the
first time I can see how Glonass makes the hole smaller than GPS alone
!
Also I am using firmware 2.01 in the M8N - so as to do RTK.
Regards, Geoff (Christchurch, New Zealand).
# <name>Ublox receiver</name>
# Unit type: Ublox timing receiver
# SW: 2.01 (75350)
# HW: 00080000
# ROM: 2.01 (75331)
#
#
# 07:46:54.000 UTC 20 Dec 2016 - interval 1 seconds
#
# tow accu(ns) frac(ns) sawtooth temp(C) sats
07:46:54,200831,5.000000,432505.000000,7.672000,0.000000,19
#! new reciever mode: 3D positioning: at tow 200831
#! new minor alarm state 0080: LEAP PENDING! : at tow 200831
07:46:55,200832,5.000000,432592.000000,3.694000,0.000000,19
07:46:56,200833,5.000000,432679.000000,-0.254000,0.000000,19
07:46:57,200834,5.000000,432767.000000,-4.261000,0.000000,19
#
# The following shows "clock" adjusting to be within 0.5ms of GPS reference.
#
07:59:44,201601,6.000000,499848.000000,-1.371000,0.000000,18
07:59:45,201602,6.000000,499935.000000,-4.767000,0.000000,18
07:59:46,201603,6.000000,500022.000000,-8.280000,0.000000,18
07:59:47,201604,6.000000,-499891.000000,8.944000,0.000000,18
07:59:48,201605,6.000000,-499804.000000,5.431000,0.000000,18
07:59:49,201606,6.000000,-499717.000000,1.860000,0.000000,18
#
# End of nights run !
#
18:53:06,240803,5.000000,67960.000000,6.446000,0.000000,19
18:53:07,240804,5.000000,67821.000000,-0.328000,0.000000,19
18:53:08,240805,5.000000,67682.000000,-6.074000,0.000000,19
#
# Accu ADEV over 40081 points - sample period=1.000 secs
# 1.000 tau 7.2040e-011 (n=32998)
# 2.000 tau 4.8366e-011 (n=32996)
# 5.000 tau 2.8732e-011 (n=32990)
# 10.000 tau 1.9632e-011 (n=32980)
# 20.000 tau 1.3585e-011 (n=32960)
# 50.000 tau 7.5530e-012 (n=32900)
# 100.000 tau 4.6426e-012 (n=32800)
# 200.000 tau 2.6046e-012 (n=32600)
# 500.000 tau 1.3244e-012 (n=32000)
# 1000.000 tau 8.7194e-013 (n=31000)
# 2000.000 tau 5.2908e-013 (n=29000)
# 5000.000 tau 1.9171e-013 (n=23000)
# 10000.000 tau 1.2432e-013 (n=13000)
#
# Accu HDEV over 40081 points - sample period=1.000 secs
# 1.000 tau 7.2902e-011 (n=32997)
# 2.000 tau 4.8859e-011 (n=32994)
# 5.000 tau 2.8982e-011 (n=32985)
# 10.000 tau 1.9672e-011 (n=32970)
# 20.000 tau 1.3796e-011 (n=32940)
# 50.000 tau 7.7782e-012 (n=32850)
# 100.000 tau 4.8215e-012 (n=32700)
# 200.000 tau 2.6956e-012 (n=32400)
# 500.000 tau 1.3305e-012 (n=31500)
# 1000.000 tau 8.8066e-013 (n=30000)
# 2000.000 tau 5.0519e-013 (n=27000)
# 5000.000 tau 1.8091e-013 (n=18000)
# 10000.000 tau 1.1809e-013 (n=3000)
#
# Accu MDEV over 40081 points - sample period=1.000 secs
# 1.000 tau 7.2040e-011 (n=32998)
# 2.000 tau 3.7837e-011 (n=32995)
# 5.000 tau 2.0161e-011 (n=32986)
# 10.000 tau 1.3699e-011 (n=32971)
# 20.000 tau 9.3194e-012 (n=32941)
# 50.000 tau 4.9118e-012 (n=32851)
# 100.000 tau 2.9460e-012 (n=32701)
# 200.000 tau 1.5282e-012 (n=32401)
# 500.000 tau 8.0902e-013 (n=31501)
# 1000.000 tau 5.1762e-013 (n=30001)
# 2000.000 tau 3.3773e-013 (n=27001)
# 5000.000 tau 9.1508e-014 (n=18001)
# 10000.000 tau 6.2193e-014 (n=3001)
#
# Accu TDEV over 40081 points - sample period=1.000 secs
# 1.000 tau 4.1592e-011 (n=32998)
# 2.000 tau 4.3691e-011 (n=32995)
# 5.000 tau 5.8201e-011 (n=32986)
# 10.000 tau 7.9093e-011 (n=32971)
# 20.000 tau 1.0761e-010 (n=32941)
# 50.000 tau 1.4179e-010 (n=32851)
# 100.000 tau 1.7009e-010 (n=32701)
# 200.000 tau 1.7646e-010 (n=32401)
# 500.000 tau 2.3354e-010 (n=31501)
# 1000.000 tau 2.9885e-010 (n=30001)
# 2000.000 tau 3.8997e-010 (n=27001)
# 5000.000 tau 2.6416e-010 (n=18001)
# 10000.000 tau 3.5907e-010 (n=3001)
#
# Frac ADEV over 40081 points - sample period=1.000 secs
# 1.000 tau 8.6517e-004 (n=32998)
# 2.000 tau 6.1178e-004 (n=32996)
# 5.000 tau 3.8695e-004 (n=32990)
# 10.000 tau 2.7365e-004 (n=32980)
# 20.000 tau 1.9355e-004 (n=32960)
# 50.000 tau 1.2250e-004 (n=32900)
# 100.000 tau 8.6732e-005 (n=32800)
# 200.000 tau 6.1484e-005 (n=32600)
# 500.000 tau 3.8542e-005 (n=32000)
# 1000.000 tau 2.5388e-005 (n=31000)
# 2000.000 tau 1.7593e-005 (n=29000)
# 5000.000 tau 1.1647e-005 (n=23000)
# 10000.000 tau 4.9191e-006 (n=13000)
#
# Frac HDEV over 40081 points - sample period=1.000 secs
# 1.000 tau 8.6518e-004 (n=32997)
# 2.000 tau 6.1180e-004 (n=32994)
# 5.000 tau 3.8698e-004 (n=32985)
# 10.000 tau 2.7369e-004 (n=32970)
# 20.000 tau 1.9360e-004 (n=32940)
# 50.000 tau 1.2258e-004 (n=32850)
# 100.000 tau 8.6841e-005 (n=32700)
# 200.000 tau 6.1639e-005 (n=32400)
# 500.000 tau 3.7430e-005 (n=31500)
# 1000.000 tau 2.4097e-005 (n=30000)
# 2000.000 tau 1.7484e-005 (n=27000)
# 5000.000 tau 1.3218e-005 (n=18000)
# 10000.000 tau 4.9282e-006 (n=3000)
#
# Frac MDEV over 40081 points - sample period=1.000 secs
# 1.000 tau 8.6517e-004 (n=32998)
# 2.000 tau 4.8366e-004 (n=32995)
# 5.000 tau 2.7905e-004 (n=32986)
# 10.000 tau 1.9449e-004 (n=32971)
# 20.000 tau 1.3706e-004 (n=32941)
# 50.000 tau 8.6694e-005 (n=32851)
# 100.000 tau 6.1408e-005 (n=32701)
# 200.000 tau 4.3586e-005 (n=32401)
# 500.000 tau 2.5653e-005 (n=31501)
# 1000.000 tau 1.7418e-005 (n=30001)
# 2000.000 tau 1.2215e-005 (n=27001)
# 5000.000 tau 8.4702e-006 (n=18001)
# 10000.000 tau 8.6617e-007 (n=3001)
#
# Frac TDEV over 40081 points - sample period=1.000 secs
# 1.000 tau 4.9951e-004 (n=32998)
# 2.000 tau 5.5849e-004 (n=32995)
# 5.000 tau 8.0555e-004 (n=32986)
# 10.000 tau 1.1229e-003 (n=32971)
# 20.000 tau 1.5827e-003 (n=32941)
# 50.000 tau 2.5026e-003 (n=32851)
# 100.000 tau 3.5454e-003 (n=32701)
# 200.000 tau 5.0328e-003 (n=32401)
# 500.000 tau 7.4054e-003 (n=31501)
# 1000.000 tau 1.0056e-002 (n=30001)
# 2000.000 tau 1.4104e-002 (n=27001)
# 5000.000 tau 2.4451e-002 (n=18001)
# 10000.000 tau 5.0008e-003 (n=3001)
#
#
#*** 708929 Rcvr packets processed. 0 bad packets.
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