[time-nuts] Signav GPS timing receivers

[Randy Warner]

Magnus et al,

The TM3 is currently undergoing final software tweaks and should be
available by February (but you know how software schedules go....) They
will be slightly less expensive than the M12M receivers.

The basic chip is the u-NAV. There are a couple different versions,
although the -01 will be the initial release. This receiver communicates
in both SiRF binary (yes, it's officially SiRF binary now) and NMEA
protocols at 4800, 9600, 19,200, and 57,600. It also has onboard FLASH
so that you can save setup information.

I'll keep you guys informed as I learn more.


Randy Warner
Senior Applications Engineer
Synergy Systems, LLC
randy at synergy-gps.com

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Magnus Danielson
Sent: Saturday, December 30, 2006 8:53 PM
To: time-nuts at febo.com; bruce.griffiths at xtra.co.nz
Subject: Re: [time-nuts] Signav GPS timing receivers

From: Dr Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] Signav GPS timing receivers
Date: Sun, 31 Dec 2006 15:59:45 +1300
Message-ID: <459727A1.5040100 at xtra.co.nz>

Bruce,

> Has anyone used any of the following signav receivers for timing
purposes.
> They claim to actually correct the sawtooth error in hardware.
> 
> http://www.signav.com/index_files/PDF_Files/New_Brochures/SigNav%20TM3
> -01%20Brochure%20V1.2.pdf
> 
> http://www.signav.com/index_files/PDF_Files/New_Brochures/SigNav%20TM3
> -02%20Brochure%20V1.2.pdf
> 
> http://www.signav.com/index_files/PDF_Files/New_Brochures/SigNav%20Bro
> chure%20TM3%20Evaluation%20Kit%20V1.1.pdf
> 
> The receiver oscillator is disciplined to "eliminate" sawtooth
correction.
> The 2nd has a 10Mhz 1E-8 stability reference frequency output.

Considering the options, I'd say that this is basically a modernized
version of the Allstar/Superstar receivers. Most probably it is the
Zarlink GP4020/GP2015 chipset at work. The other posibility (uNav) does
not neatly match frequencies and the GP4020 has two extra divide
counters which makes the clock output on the TM3-02 very easy to
acheive. The GP4020 also provides a handy SPI interface so hooking up an
external SPI DAC for EFC is trivial. The GP4020 has a refined PPS output
compared to the old GP2021, but it is an interesting "hack" ontop of the
old core, something which could be used to enhance older receivers if
one wishes. That way the 7 second beating pattern can be avoided.
Naturally, that
7 second pattern is very predictable and could be included in negative
sawtooth output if you where going down that route.

The core clock is at 40 MHz in those, so a stepup from 10 MHz is trivial
(and indeed how it is done). Also delivering 10 MHz and 1 kHz outputs
should not meet any interesting issues at all.

It is interesting how they are targeting the M12+/M12M market. Looks
like a sweet deal. If you look down their webpages, they seem to have
put alot of their effort into the backend processing, including Kalman
filtering, doppler processing to dead-reckoning moving vehicles with too
few satellites in view etc. All quite doable on the old receiver cores
as such, but takes bigger footprint in software. Looks quite
interesting.

Randy said earlier that he where going to sell them, but they don't seem
to have appeared on their web. What is your asking for one of these? I'd
sure like to run it against some other stuff here.

PS. My newly arrived Symmetricom 56k locked up this evening. There's now
another GPSDO in the house featuring both Rb (a TEMEX Rb) and OCXO (OSA
8666).

Cheers,
Magnus

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