[time-nuts] Common sky pps errors for any GPSDOs?

Matt Ettus boyscout at gmail.com
Mon Jan 5 17:31:57 EST 2009

On Mon, Jan 5, 2009 at 1:54 PM, Bruce Griffiths
<bruce.griffiths at xtra.co.nz> wrote:

> If the application is somewhat analogous to VLBI, then the maximum
> (uncorrectable ie random) allowable carrier frequency phase errors
> between receivers depends on the integration time.
> Maximum integration times for VLBI are typically 10,000 sec or less,
> with corresponding relative ADEV (after correction for drift etc) on the
> order of 1E-14 (or better) @ 10,000 sec for a carrier frequency of a few
> GHz.
> What is the integration time in your application?

We are trying to receive data which is modulated at rates which vary,
but are in the 100 Hz to 100 kHz range, so the integration times are
very short, all below 10ms.

> What is the carrier frequency?

30 MHz and below for now, but we'd like to be able to go as high as
500 MHz or so.

> For short integration times most rubidium standards are much noisier
> than a good OCXO.
> GPS carrier phase techniques will allow lower noise comparisons of LO
> phase differences than a GPS derived PPS based system.

Don't the Rb standards end up disciplining an OCXO so you get the
benefit of the crystal at the shortest integration times?


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