[time-nuts] Precise manual survey (was Common sky pps...)

[SAIDJACK at aol.com]

Hello Peter,
 
I would think it's related to 1ns per foot, but depends highly on Sat  
geometry at any given time. I remember talking about this some years ago on time  
nuts, and someone mentioned it wasn't exactly 1ns/foot, but slightly less (if I  
remember correctly).
 
Yes, the cable delay is completely independent of the "wobble", since all  
sat's signals will be delayed equally long. The cable delay just causes a  
static phase-offset in the UTC 1PPS pulse. This can be compensated for in  1ns 
steps on our Fury GPSDO.
 
There are some secondary effects such as multipath signals that can also  
have a detrimental effect on precision, so the antenna quality and it's  
placement can also help reduce the wobble. The Motorola M12+ manual has some  nice 
explanations and drawings to this effect. I think timing receivers have a  much 
easier time detecting multipath, and rejecting it than 3D fix receivers  since 
timing receivers can over-determine their position/time resolution.
 
bye,
Said
 
 
In a message dated 1/7/2009 08:02:59 Pacific Standard Time,  
pvince at theiet.org writes:

Thanks  Said.  A supplementary question, if I may: can you confirm that the  
phase
"wobble" caused would be a maximum of the usual 1ns per foot?   And am I 
right in
thinking that incorrectly specifying the antenna cable  delay will only 
affect the
accuracy of the timing of the 1pps output wrt  UTC, and not cause any extra 
wobble?

Thanks,

Peter