[time-nuts] PPS phase between two GPS units.
paulswedb at gmail.com
Wed Dec 23 13:11:00 EST 2015
Great and at least for me it makes sense from the active splitters I have
seen that use diodes to allow one receiver to power the pre-amp.
In my 8 way you have the diodes and L+Cs. The powered path is essentially
the diode turned on.
The non powered is a reverse biased diode and the C around the diode and
then the Ls of the DC path. Something like that.
I did the same thing as you in the 8 way splitter.
Separate DC bias feeding upstream to a intermediate amp ahead of the
splitter to make up for the 8 way splitter loss about 16 db as I recall.
With humor I am finding 8 ports isn't quite enough! Silly.
On Wed, Dec 23, 2015 at 11:11 AM, Dan Kemppainen <dan at irtelemetrics.com>
> 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.
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