[time-nuts] NEO-M8N vs. NEO-M8T

Gary E. Miller gem at rellim.com
Mon May 21 15:33:46 EDT 2018

Yo Mark!

On Mon, 21 May 2018 19:21:25 +0000
Mark Sims <holrum at hotmail.com> wrote:

> It looks like you have slipped a decimal point somewhere (also that
> "ps" label is wrong).

Yes, seemed 10x too high to me too.  But the doc for UBX-TIM-TP clearly
says 'ps'.

    qErr ps Quantization error of time pulse (not supported
            for the FTS product variant).

Here is another data point, with the raw data so you can check the decode:

Class: TIM(0xd) ID: TP(0x1), len: 0x10
payload: f0fb550900000000e7d6ffffd2070a00
tow:1566300.000000000 qErr:-0.000000105210 ps, week:2002
  flags:0xa refInfo:0x0
      is GPS, UTC available

Sure looks like 105 nano seconds to me.  If I'm wrong I'd love to know

> I have an M8N running here and the report
> sawtooth errors are all within a +/- 10 ns span.   (and LEA-5T is +/-
> 5ns).

Many things could explain the difference.  We seem to only differ by 5x
or 10x.

Also, my ADEV plot clearly showed the NEO-M8N adev was better than the
NEO-M8T adev at tau=0, so your observations match mine.

Right now I'm doing a survey-in.  Then I'll grab a days worth of TICC
data.  After that I'll go back and get long term standard deviations
for qErr in Stationary and Survey-in modes.  That, of course, will take

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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