[time-nuts] U-blox teaser

[John Ackermann N8UR]

They're claiming "even better than" 5 ns for relative time, which given 
the 4 ns jitter seems at least sort-of reasonable.  But until someone 
shows me otherwise, I'm still thinking that getting better than 25 ns 
absolute accuracy is a pretty good day's work.

John
----

On 2/26/21 5:26 PM, Bob kb8tq wrote:
> Hi
> 
> I can’t think of many antennas (multi band or single band) that claim to know their
> delay to < 5 ns. Simply having a *differential* delay spec of < 5 ns is quite good.
> Same thing with delay ripple, you see specs out to around 15 ns on a lot of antennas.
> None of this is getting you to the actual total delay of the antenna. It’s a pretty good
> bet that number is a bit larger than either of these.
> 
> Some of the ripple probably comes out in the standard modeling. I’m not sure that
> the differential delay is taken out that way. Total delay, not taken out in any obvious
> fashion ( at least that I can see). If the F9 has a built in antenna database, that’s not
> mentioned in the doc’s. Any benefit from the corrections would have to be part of
> post processing.
> 
> No, that’s not the same as talking about the F9 it’s self doing X ns, but it would be part
> of any practical system trying to get close to 5 ns absolute accuracy.
> 
> 5 ns *relative* accuracy between two F9’s? I probably could buy that if the appropriate
> one sigma / on a clear day / with the wind in the right direction sort of qualifiers are
> attached.
> 
> Bob
> 
>> On Feb 26, 2021, at 4:27 PM, John Ackermann N8UR <jra at febo.com> wrote:
>>
>> It's interesting that they talk about the F9 receivers offering 5 ns absolute time accuracy.  Does anyone know of tests confirming that, and what sort of care was required in the setup to get there?
>>
>> John
>> ----
>>
>> On 2/26/21 9:34 AM, Robert LaJeunesse wrote:
>>> FWIW. No detailed content, and a rather quick read. "Five key trends in GPS".
>>> https://www.u-blox.com/en/blogs/insights/five-key-trends-gps
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