To: rsgb_lf_group@blacksheep.org
From: Paul Nicholson <vlf0403@abelian.org>
Message-ID: <7dced87f-1e6e-0549-7693-2ebd0c19a630@abelian.org>
Date: Sat, 10 Feb 2018 20:33:18 +0000
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Subject: LF: u-blox NEO-M8T timing GPS
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I've just started experimenting with a couple of NEO-M8T
boards.  It's the first time I've used the M8T.  It's designed
particularly for timing applications.

It appears immediately impressive compared to the already good
NEO-7 series.   It's picking up a lot more satellites from
the poor antenna location on the window ledge.  It computes
a fix and time using GPS, GLONASS and Galileo networks!

Just hooked one up to a Pi and stereo audioinjector card and
it's giving 21nS PPS jitter just with a breadboarded PPS
shaper on the bench.

It has a mode of operation, which I've yet to try, where
it fixes its position and then concentrates on getting
accurate timing pulses.  I'm looking forward to firing that up,
on a good GPS antenna.

It also has two independently programmable timepulse ouputs,
which I need for my LF receiver - a 2mS PPS pulse to time the
Octo sample rate, and a 103kHz local oscillator.

Rather more expensive than the other u-blox GPS modules but it
looks worth it.

My source is CSG shop, located in Latvia.  I've had two
deliveries so far from them with no problem.  Shipment can
take a while, took nearly a month for the first order but the
second was less than 10 days.  Tracking showed the first spent
a lot of time in Latvia post and then about a week in a
depot at Heathrow airport!

I bought two models:

First,

  http://www.csgshop.com/product.php?id_product=218

which also needs

  http://www.csgshop.com/product.php?id_product=216
  http://www.csgshop.com/product.php?id_product=217

plus a pigtail for the microscopic U.FL antenna connector, eg

  https://www.amazon.co.uk/dp/B01LPXGJ2I/

The other board is

  http://www.csgshop.com/product.php?id_product=240

which also needs a little breakout board

  http://www.csgshop.com/product.php?id_product=239

There is a third M8T board, product code 205 but this doesn't
appear to have the 2nd timepulse brought out.

So far I'm well impressed.  Exchanged some emails with Aleks
Ivanovs who runs the shop.  Helpful, and he'll do custom boards
to whatever our requirements might be.  Worth a look at all
the other gadgets he supplies.

The only other source I've found for M8T boards is u-blox
themselves with their very expensive evaluation board.

--
Paul Nicholson
--