[time-nuts] Fwd: CGSIC: FW: New NANU 2014090

Jim Lux jimlux at earthlink.net
Wed Dec 17 09:01:17 EST 2014

On 12/17/14, 5:20 AM, Dan Kemppainen wrote:
> Not sure if this is quite the right platform, but for someone wanting to
> experiment it may be worth a look...
> https://www.kickstarter.com/projects/swiftnav/piksi-the-rtk-gps-receiver
> http://www.swiftnav.com/piksi.html
from that page:
3-bit, 16.368 MS/s L1 front-end supports


It uses the MAX2769, which has a tuning range of 1550-1610.


We get good results at JPL with direct conversion receivers (versus the 
MAX 2769 is basically a single conversion superhet).. a chain of 
amplifiers and BPFs followed by a one bit quantizer like an ECL D 
flipflop clocked by the reference clock chosen to put the aliases at 
convenient places in band.

I suspect, though, that the "wide open" LNA in the typical JPL receiver 
is susceptible to interference. Most "survey quality" receivers (except 
from Javad, which are "LightSquared Ready"<grin>) have pretty bad 
interference rejection: they want the least stuff that might introduce a 
phase shift in the signal path:  It's all basic time-nuts stuff.. you 
get that precise position by knowing what the carrier phase is to a 
fraction of a gnat's eyelash.

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