[time-nuts] Delay through GPS antenna splitter/amplifier -- an answer, and a question
John Ackermann N8UR
jra at febo.com
Mon Mar 12 12:51:19 EDT 2007
In short, yes. If you want true traceability to NIST, you need to take
into account UTC(GPS) versus UTC(NIST).
I don't think you would do this by adjusting the cable delay, because
that offset will change over time. Instead, you post-process by getting
the offset for the time during which you made the measurement, and
adding it to your solution.
Jason Rabel wrote:
> Since we are on the subject... I came across this page the other day and am
> curious about what other's thoughts are about it.
> If I understand correctly looking at the graphs, they are saying the time
> from GPS is currently off about 24-30ns from the NIST frequency standard. So
> does that mean that a person wanting every last ns should adjust their delay
> according to the data on that page (and of course things like cable delay
> and other circuitry)?
>> But we're time-nuts... we DO worry about those things. :-)
>> While we were at it with the network analyzer, we did FDR (frequency
>> domain reflectometry) to measure the cable delay to the antenna, and I
>> spent yesterday making up six matched cables to go from the splitter to
>> the receivers -- they all test within about 1 nanosecond of each other.
>> Obsessive compulsive? Me?
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