[time-nuts] need recomendation for a portable 10mhz reference oscilator

[Magnus Danielson]

From: bg <bg at lysator.liu.se>
Subject: Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator
Date: Wed, 12 Dec 2007 06:58:15 +0100
Message-ID: <1197439095.11811.3.camel at bg-desktop>

> 
> On Tue, 2007-12-11 at 18:38 -0500, John Ackermann N8UR wrote:
> 
> > To get decent (for some definition of "decent") timing, you need to
> > operate the receiver in "0-D" mode, telling it where it is and letting
> > it solve just for time.  I haven't done the experiments myself but I
> > believe that the time accuracy is pretty dramatically degraded when
> > operating in 2-D or 3-D mode.
> > 
> > > How long does a survey take (in good conditions) and what sort of time 
> > > constant would you want to use with a navigation box?
> > 
> > It depends on the receiver, but usually it's a few hours to a full day.
> >  Of course, if you use external software you can use whatever time
> > period you want.
> > 
> > John
> 
> I am surprised surveying mode is needed anymore. In a SA environment it
> makes sense, but for me its hard to understand with the current accuracy
> given by the GPS system.

For the 2,13E-9 precission needed, very simple arrangements should be needed
around a standard GPS receiver. No fancy features like sawtooth correction and
TRAIM needed. My little bluetooth-GPS would do after a very mild modification
(PPS output).

If you use a OSA 8712 together with a simple GPS, only very simple control
should be needed. Powerbudget and price could be held fairly low.

The optimum design does not always relate to optimum Allan Deviation curve you
know. :)

Cheers,
Magnus