[time-nuts] Time Transfer

[Didier Juges]

Hi Brooke,

Thank you for your suggestions, that page is probably ripe for a rewrite,
but I may just add a link to your page for now :-)

I would have thought the GPS receiver averages the readings when it locks on
multiple satellites. Are you saying it only uses one at a time? If so,
what's the point of a self survey?

I talk about WWV because most ham operators have a receiver that receives
WWV, so it is an inexpensive and convenient way to get an absolute
reference, even though it is not as good as GPS.

I am sure there is a reason why timing receivers track all the way down,
instead of switching to a better bird when one is available, but by setting
the mask angle fairly high (appropriate for your location and obstructions),
you can take care of this problem.

Didier KO4BB

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Brooke Clarke
> Sent: Friday, December 14, 2007 2:16 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] Time Transfer
> 
> Hi Didier:
> 
> Been surfing your Timing web page and came across 
> http://www.ko4bb.com/Timing/FrequencyReference.html
> Got there by working up the URL for the Vig paper.
> 
> An ordered list of Time Transfer methods from carrier phase 
> GPS to the Astrolabe is at:  http://www.prc68.com/I/timefreq.shtml#TT
> that ranks HF time stations far below other methods, so 
> although they can be used there may be better choices that 
> are affordable.
> 
> Also for GPS timing applications (i.e. the GPS receiver is in 
> position hold
> mode) a single satellite is all that's needed.  Adding more 
> satellites can add a failure alarm function but may not 
> improve accuracy.  In my case multipath is a big problem so a 
> high elevation mask is needed.
> 
> The problem with a less than 12 channel receiver relates to 
> how satellites are selected.  The Motorola timing receivers 
> will continue to track a satellite until it sets rather than 
> switch to a a new one which may be directly overhead. 
>   The "use highest in the sky" applies to how a new satellite 
> is selected. 
> Once selected the satellite is tracked until it sets.
> 
> An idea: When averaging GPS 1 PPS signals the receiver 
> switches satellites as the currently tracked ones set so 
> there may be a slight change in accuracy because of the 
> satellites being used.  But changing from a satellite that's 
> about to set i.e. that has a lot of multipath to high in the 
> sky sat should make for a better 1 PPS.
> 
> -- 
> Have Fun,
> 
> Brooke Clarke
> http://www.PRC68.com
> http://www.precisionclock.com
> http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.