[time-nuts] PPS phase between two GPS units.

Tommy Phone tholmes at woh.rr.com
Wed Dec 23 13:14:50 EST 2015


Seems to me you could adjust the feed line length value in one of the receivers to zero out the difference as it appears that the path length is slightly different.

From Tom Holmes, N8ZM

> On Dec 23, 2015, at 11:11 AM, Dan Kemppainen <dan at irtelemetrics.com> wrote:
> 
> Hi all,
> 
> Thanks for all the responses.
> 
> The GPS units were swapped on the splitter ports, and the phase difference did in fact change. It changed from 21nS to around 5nS. Not exactly what was expected, although it would tend to indicate the RF path is not the same through the splitter.
> 
> Last night a 'symmetrical splitter' was made up using a mini circuits ZFRSC-42. Both of the outputs to the GPS units were AC coupled. A bias T was inserted directly on the antenna feed with external power feeding the new splitter antenna port.
> 
> The PPS's are now very close, about 1 nS average difference. If this holds solid, in a few days I'll swap splitter ports again.
> 
> Thanks,
> Dan
> 
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