Reference clocks.

[Hal Murray]

verm at darkbeer.org said:
>> What's your current collection?
> I don't have any right now other than the various GPS chips and boards on
> the  way to run off of GPIO connections. 

You should probably get a couple of the USB "mice" or hockey puck style 
units.  They run $25-$50 each.  Most speak NMEA and don't have PPS.

SiRF used to have most of the market but I think uBlox is getting in there 
now.  Eric reports that gpsd had nasty troubles with the SiRF-S4 aka Star Vi. 
 It's newer than the -S3 (aka Star III) so I expect the S3 may be impossible 
to get any more.  If you can find one, I'd grab it unless the price is insane.

Odroid has a uBlox USB unit for $25.

It would be good to be able to test PPS over USB.  The no-soldering approach 
is to get one of the 601W.  (I think that's the right number.)  Gary may 
still have some or Mark may order a batch.

The soldering approach is to get a Sparkfun breakout board and a USB-serial 
breakout and add several wires.

For a real serial port, the Garmin GPS-18X LVC has PPS but needs soldering 
and power.  You can steal power from USB.


There are 2 flavors of GPSDOs that are popular with hackers and hams because 
they have been widely available on the surplus/recycled market at reasonable 
prices.  They are older units so they need a good antenna location.  One is 
the Trimble Thunderbolt.  I think it was used in 911 call centers.  The other 
is the HP Z3801A.  I think it was used in cell phone towers.  There are 
various other Z38xx units that speak roughly the same protocol and there is a 
5xxxx part number for the still in production version.

They tend to show up on eBay in batches.  There is no current good deal.  
There is a TBolt with power supply and antenna for $450.  There is a package 
that claims to be a Z3801A for $450.  I don't know what it really is.  The 
picture is not the old/real Z3801A.



-- 
These are my opinions.  I hate spam.