[time-nuts] Novatel Dual frequency GNSS receivers on ebay

Tom Van Baak tvb at LeapSecond.com
Mon Oct 9 16:02:32 EDT 2017


Thanks for that additional information. Can you (or Gregory) also comment on the external frequency input / output and the 1PPS output of this receiver?

A quick look at the om-20000128.pdf and om-20000129.pdf documents has words like "better than 250 ns accuracy" and "50 ns increments" but I didn't see mention of 1PPS quantization, sawtooth correction, or other words commonly used in GPS timing receiver specifications. I'm guessing this product is mostly designed for the PN part of PNT (Positioning, Navigation, Timing)?


----- Original Message ----- 
From: "Christopher Hoover" <ch at murgatroid.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Monday, October 09, 2017 12:35 PM
Subject: Re: [time-nuts] Novatel Dual frequency GNSS receivers on ebay

>I have quite a bit of experience with Novatel hardware include OEM6, CPT
> and SPAN.
> CPT is an IMU made by KVH and relabeled by Novatel.    The accelerometers
> are MEMs and the roll rate sensors are FOGs.   Pretty old design.
> Performance is decent (but not auto alignment good).
> http://www.kvh.com/Military-and-Government/Gyros-and-Inertial-Systems-and-Compasses/Gyros-and-IMUs-and-INS/IMUs/CG-5100.aspx
> SPAN is the "solution."    SPAN-CPT puts the CPT IMU and the receiver in a
> single box.   You could also get just the CPT in a box.
> The feature set enabled depends on the software keys that are loaded.
> Caveat emptor.
> Dual receiver (even if you have the hardware) and ALIGN feature are extra
> features.
> Also worth noting is that the circular connectors used on some of the
> hardware are pricey.  Some are impossible to assemble without specialty
> tools.
> -- Christopher.
> 73 de AI6KG
> On Sat, Oct 7, 2017 at 2:36 PM, J. L. Trantham <jltran at att.net> wrote:
>> Any idea what they are selling for at this time?
>> I see that some sold for the BIN price of $349.99 up until June 20.  After
>> that, 'Offer Accepted' occurred up through October 5, with a BIN price now
>> of $649.99, all plus $40 shipping.
>> Joe
>> -----Original Message-----
>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Gregory
>> Maxwell
>> Sent: Saturday, October 07, 2017 2:17 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] Novatel Dual frequency GNSS receivers on ebay
>> There is an ebay listing for "Novatel GPS-702-GG with SPAN-CPT Single
>> Enclosure GNSS/INS Receiver + Cable" with a fairly large number available.
>> This is a Novatel OEM628 dual frequency receiver (supports GPS, Glonass,
>> SBAS, apparently including L1C and L2C), plus a three fiber ring gyros
>> (with bias performance that blows away any mems gyro I've ever used) and an
>> 3-axis mems acceletrometer in an aluminum case, plus a decent dual
>> frequency antenna.  This is a generation-ish old kit.
>> The industrial casing conspires to make it look somewhat less modern than
>> it actually is.
>> The receivers have external clock input (though not plumbed to the outside
>> of the case) which appears to work though I didn't try much with it yet.
>> Mine came with 2013-ish firmware but easily upgraded to current (2016)
>> firmware. There is a windows based firmware update tool which talks to it
>> over serial and is very straight forward (The firmware update OEM6631.zip
>> can be found via google).
>> You can communicate with them over serial in ascii, there is extensive
>> firmware documentation that goes over every command
>> https://www.novatel.com/assets/Documents/Manuals/om-20000129.pdf  some of
>> which are specific to other modules. There is also a separate manual for
>> the inertial navigation specific features (NovAtel SPAN-CPT Users
>> manual.pdf)
>> The external clock should allow you to hang it off a more stable
>> oscillator which will improve the stability of the GNSS results, and _I
>> presume_ improve the quality of the PPS output-- the firmware manual and
>> operating manual are thin on details, and mostly just go into telling you
>> how to adjust the kalman filter constants for different clock types.
>> These also appear to support the novatel 'align' mode where you serial
>> connect two receivers separated by a short baseline and get really accurate
>> absolute headings; I'm planning on trying that that but haven't set it up
>> yet.
>> Looks like uber (last position was ubers offices in denver) had a fleet of
>> these things. The couple I got run great, including the IMU, the antennas
>> obviously spent a long time outside, but work fine. The cable they come
>> with is weird, but I had no problem chopping one end off and figuring out
>> the pinout (see bottom).
>> The novatel OEM6 is well supported by rtklib and I was able to get
>> post-processed positions very easily.
>> Seller takes best offers a fair amount below the $649 asking price.
>> Looks like they may have another 30 or so of them.
>> May be useful for doing time transfer especially with the clock input.
>> Just using it to get nice dual band observations to precisely survey an
>> antenna location for a traditional GPSDO may improve GPSDO performance by a
>> fair amount.
>> Here is the signals and wire colors on the cables mine came with.
>> YMMV, I'd suggest not blindly trusting that colors match on other
>> units.    These cables don't plumb out many of the signals from the
>> module (in particular, they don't carrying COM2, which is why I haven't
>> tried multi-receiver headings yet, since I'd need to figure out how to talk
>> to it over USB if com1 is in use for that), I'm unsure if they're wired
>> through the to external connector.
>> 01 white          power return (-)
>> 02 brown          9-18 VDC power input (+)
>> 03 yellow        COM1 RS232 TX
>> 05 pink           COM1 RS232 RX
>> 09 green          COM1 GND
>> 10 black          USB D+
>> 11 purple         USB D-
>> 12 yellow brnstp  USB GND
>> 15 red            ODO SIGA
>> 16 blue           ODO SIGA-inv
>> 29 grey pinkstp   PPS (high resistance? 80 ohm)
>> 30 whitw grnstp   Event1
>> 31 red blustp     signal ground
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