[time-nuts] U-blox teaser

[Bob kb8tq]

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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