Re: ✘NEO-M9N

[Frank Nicholas]

Thanks for the info.

On Feb 11, 2020, at 9:56 PM, Gary E. Miller <address@hidden> wrote:

Yo Frank!

On Tue, 11 Feb 2020 21:19:23 -0500
Frank Nicholas <address@hidden> wrote:

I purchased this module, with the same chip, in December - haven't
had a chance to play with it yet:
https://www.sparkfun.com/products/15712
<https://www.sparkfun.com/products/15712>

It's more expensive and has some other options/connectors.  

I think the GNSS 7 is somewhat better:

Price:              $40          $65
Antenna Connector:  SMA          u.fl
Backup:             Super Cap    battery
Berg Pins:          Installed    Just holes
Size:               57x25 mm     40x33 mm
Mounting holes      No           Yes

Site for the product you linked says Backup:  “Battery Holder + Battery”.   I usually, envtually hard-wire my dev boards (soldered wires) to whatever I’m working with (another board, or DB9), and I have rows of header pins laying around if I need them.  The Sparkfun board can be powered by 5V (logic is still only 3.3V) — there is a hole/pin for 5V input for power.  It’s also “Open Hardware”, released under the Creative Commons Attribution Share-Alike 4.0 License.  I see +/- for both boards (cost especially for the board you linked).

I had some holiday discounts/coupons that prompted me to pull the trigger on the Sparkfun purchase - I’m a long time customer of theirs.  I’m also invested in their Qwiic I2C cabling system (I know it’s a simple 4 wire connector/cable, but to get a new breakout board, and just “plug it in” to start playing/testing is instant gratification!)  I have many Auriono compatble/ESP32/Pi devices with Qwiic connectors.  Even Adafruit is now making breakout/SoC boards with Qwiic connectors.

There is a lot of official/good uBlox documentation linked from the Sparkfun uBlox product pages for the board & antenna (see antenna mentioned below)

I didn't know what Gary's "L1 only" was referring to. I found this
clear explanation:
https://www.mapleprecision.com/2019/01/16/l1-l2-l5-satellite-signals/
<https://www.mapleprecision.com/2019/01/16/l1-l2-l5-satellite-signals/>

A start, but more complicated than that. That only applies to GPS, but
the NEO-M9N can also recieve GLONASS (L1), Galileo (E1), IMEI (L1)
and BeiDou (B1).  Which are all kinda sorta, not quite, in the same
frequency range as GPS L1.

Here is a slightly more complete list if frequencies.  Look at
Figure 2:  https://gssc.esa.int/navipedia/index.php/GNSS_signal

One takeaway is that GPS antennas do not work well with modern
multi-GNSS receivers.

This is why I purchased these items with the module:

Interface Cable RP-SMA to U.FL - WRL-00662 - SparkFun Electronics

uBlox brand multi-band antenna:  GNSS Multi-Band Magnetic Mount Antenna - 5m (SMA) - GPS-15192 - SparkFun Electronics

GPS Antenna Ground Plate - GPS-15004 - SparkFun Electronics

I hope the antenna is worth the price - $64.95 USD.  With it being a uBlox part (ANN-MB-00), it might be available elsewhere for less.

For $4.95 USD, it’ll be interesting to see what/if the steel disk improves.

Is the "L1 only" a limitation of the NEO-M9N chip?

Yes.  Until the u-blox 9 series, all consumer grade GNSS receivers were
L1 (and similar) only.  The ZED-F9x receive L1 and L2 and are much more
accurate then L1 only receivers.

The advantage of L1+L2 over plain L1 is that the reciever can use the
two frequencies to cancel out the effects of the ionosphere on accuracy.

For somewhat over $200 the ZED-F9x can approach similar accuracy to
survey receivers costing thousands.  But the NEO-M9N will not be in that
class.  I'll post plots after I get the NEO-M9N that I orderd.

The antenna I linked above is “ Designed for the latest u-blox F9 platform--including the ZED-F9P module”, with “L1/L2 dual reception”.

Sparkfun has this ZED-F9P module for $219.95 USD:  SparkFun GPS-RTK2 Board - ZED-F9P (Qwiic) - GPS-15136 - SparkFun Electronics

My main hobby/use for these modules is time keeping.  Does L1 only vs. L1/L2 improve time accuracy enough to measure/matter for the cost?

RGDS
GARY
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address@hidden  Tel:+1 541 382 8588

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