[time-nuts] Ublox M8N - have I a XO or TCXO ?

Kiwi Geoff geoff36 at gmail.com
Wed Dec 21 17:30:51 EST 2016

Mike Cook wrote:
> It wouldn't surprise me, but  you have a reference for this?

I first read about this issue in the official Ublox forum Mike - try this link,


 - at time of writing it leads to some of the messages that discuss
the issue with photos and examples of M8N's that appear - not to be !

I must say, the two devices I have, appear to be genuine, and do
everything they should, and are a wonderful piece of kit.

My initial (now erroneous) thought was that maybe I could do a quick
overnight run with Lady Heather 5, to show up the M8N oscillator type.
Thanks to the excellent feedback on this thread, I now see why this is
not so, my overnight graph (seen in OP) is looking at a layer of
operation that somewhat hides the actual oscillator behaviour. I still
think it is an interesting graph, and shows the M8N can do a good job
of being a GNSS timing part.

Although as Mark S has said, it requires independent testing against a
reference to be done, rather than my graph - which essentially is the
M8N "self reporting" its quality.

>From my reading so far, the current best way to find out if you have a
genuine M8N is to use u-centre , and ask it to poll the UBX-MON-VER
command, which should return:

original firmware (2.01): SWVER 2.01 (75350) HWVER 00080000 EXTENSION
2.01 (75331) PROTVER 15.00 FIS 0xEF4015 (79189) MOD NEO-M8N-0

after firmware update to (3.01): SWVER EXT CORE 3.01 (107900) HWVER
00080000 EXTENSION ROM base 2.01 (75331) FWVER=SPG 3.01 PROTVER=18.00

Take special note of the "FIS=" (Flash Information Structure) size.

Firmware Update to 3.01 can give you the (newly turned on) Galileo
system, however some people (like me) may choose to stay with Firmware
2.01 because it allows playing the RTK game thanks to the work of:


Again, thank you for the replies to this thread, I have learned a lot,
and especially Bob Camp, who gave a nice explanation of the oscillator
in such a GNSS module.

Regards, Geoff (Christchurch, New Zealand).

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