[time-nuts] Sub mm measurements with gps timing antennas?

Attila Kinali attila at kinali.ch
Fri Apr 27 14:14:00 UTC 2012


Moin,

On Wed, 25 Apr 2012 20:45:54 -0400 (EDT)
SAIDJACK at aol.com wrote:

> > But.. is the CSAC not on the ITAR list? I would expect it to  be,
> > as even some precision OCXO and a lot of MCXO  are.
>  
> This is the beauty, they are not ITAR or HAZMAT  restricted! They received 
> approvals. 

Now THAT is really cool!

> We just published an article  about the CSAC GPSDO products we offer in the 
> Microwave Journal,  April issue, and this is listed there as one of the key 
> advantages of  CSAC's. 

Nice article, thanks!

> > Oh.. the CSAC is  that low power? I thought they are in the 1W region.
> > Good to  know...
> 
> Yes, CSAC itself rated at 115mW typical. They have a power down mode  with 
> auto-correct of the TCXO that gets to less than 30mW on average. CSAC's are  
> game changers, and no one has anything even remotely  comparable.

They indeed are!
 
> > I'm not quite sure about this. It would work if we had only to  deal with
> > one or two of devices, but with the numbers we need now, the work  would
> > probably cost more than a reel (i actually don't know what a reel  costs,
> > u-blox has not replied to my request for quotation i placed 3 weeks  ago).
> 
> A reel will cost some real $$$ if you can get it, more than removing  the 
> shields from the units, even if you are doing say 100 units.. With a proper  
> heat gun, it takes only about 20 seconds to get the shield off, without any  
> damage to the unit itself.

I just had a longer talk with a u-blox sales rep. Outcome is that they
do not sell the chips in volumes lower than 50k/year. Which means we cannot
use the chips to have easy access to the oscillator directly. Currently
they are trying to figure out, whether we're allowed to get information
about the LEA6-T module internas, so we can open the shield and replace
the TCXO.

>  
> The real question is, would a perfect 26MHz reference give you any GPS  
> position performance improvement or not, that is what would be interesting to  
> test..

According to a paper which i currently cannot find, the use of a caesium
as "oscillator" for a standard timing gps module improved the noise of the
PPS quite a bit.

Anyways.. i have to talk with the customer about this. I doubt that such
a major redesign will be possible in this revision (the devices have to
be ready by july), but it's definitly a good idea for the next version.

			Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin




More information about the Time-nuts_lists.febo.com mailing list