[time-nuts] Building a GPSDO & trouble using Jupiter-T

[Bob Camp]

Hi

To bring this back to the original point - will it help?

The basic assumption (I think) was that having multiple corrections per
second would make those corrections smaller. Since that's not the way short
term stability and noise normally works, my guess would be not. If you have
a receiver that updates 100 times a second, it's very likely that it will
have more jitter (peak to peak) on the output than one running the same
technology that updates once a second.

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Attila Kinali
Sent: Wednesday, February 01, 2012 4:14 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T

On Tue, 31 Jan 2012 16:29:07 -0800
Chris Albertson <albertson.chris at gmail.com> wrote:

> I'm pretty sure those GPS recievers that send out more frequent data,
> at say 2Hz or 5Hz are just interpolating.  It is not more accurate.
> The GPS sats only send a frame once over 6 seconds.

As Magnus already wrote, once you have a fix, you can use code tracking
to get an updated fix up to rates of 1kHz. If you use codeless P(Y)
code tracking or carrier phase tracking you can get even higher rates.

But, you can only update an already available fix, not calculate
a fresh fix from scratch at that rate. This is because carrier phase
and codeless P(Y) code tracking has an ambiguity of the phase, which
has to be first resolved by a "conventional" fix. Once you have this,
you can use those two techniques to get fixes at high rates.

			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

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