[time-nuts] Absolute phase
jerry at hanler.com
Fri Nov 17 15:25:08 EST 2017
I figured, what the heck, and just used a BNC T and it’s working.
> On Nov 17, 2017, at 12:20 PM, Magnus Danielson <magnus at rubidium.se> wrote:
> The reason I mention sharing antenna is that it takes out the difference that is natural from having different antennas and the difference in multipath.
> Sharing antenna has its own set of problems, so a suitable antenna splitter was assumed. Effectively you need to bypass DC to power the antenna, you need to amplify the signal to compensate for the loss due to the splitter, and it needs to look like an antenna to the GPS receiver, so the antenna alarm does not goes off.
> On 11/17/2017 09:01 PM, Jerry Hancock wrote:
>> Thanks, understand completely.
>> You mention “sharing an antenna”. Is there a problem with connecting the same antenna to two units? I am referring to my REF0/REF1 pair.
>>> On Nov 17, 2017, at 11:39 AM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>>> First of all, the receiver varies around some average phase.
>>> The average of two receivers may not be the same, even if sharing antenna.
>>> Their average can be offset from "absolute phase" because of offsets in the receiver, antenna cables and antenna.
>>> If you are not to careful, a GPSDO will do nicely for many applications. The more you care, the more hassle.
>>> Oh, and two GPSDOs next to each other can have significant common mode disturbance, so you can't really evaluate a GPSDO by measuring up to another GPSDO.
>>> On 11/17/2017 08:05 PM, Jerry Hancock wrote:
>>>> Granted I expect someone on this list to reply with something that makes me feel stupid, if you have two GPSDO units running side by side, should the phase delta on the 10Mhz output be zero (ideally)? Is there an absolute phase standard kept between GPSDO units as all it would take is one extra inverter in the chain to flip the phase, no?
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