Thanks for the link, Bob. I got to know both Victor Zhang and Mike
Lombardi during my
stay at Arecibo, but to my regret have never met either in person.
Dana
On Sat, Feb 27, 2021 at 6:01 PM Bob kb8tq wrote:
> Hi
>
>
>
> > On Feb 27, 2021, at 11:18 AM, Dana Whitlow
> wrote:
> >
> > Thanks, Bo
Hi
> On Feb 27, 2021, at 11:18 AM, Dana Whitlow wrote:
>
> Thanks, Bob.
>
> It seems to me that, depending on the positions of sats visible to one's GPS
> antenna and the spatial distribution of free electron density in the
> ionosphere,
> the ionospheric contribution to position errors could
k8yumdoo...@gmail.com said:
> During my Arecibo Observatory days we used NIST's TMAS service to keep our
> H-maser-based station clock synced with UTC. Our user community (mainly VLBI
> and pulsar timing people) seemed pretty satisfied with +/- 100ns accuracy, so
> I tried to do better by keepin
Dana,
> During my Arecibo Observatory days we used NIST's TMAS service to keep
> our H-maser-based station clock synced with UTC.
And before that, the observatory used Tom Clark's Oncore & SHOWTIME and
later Rick Hambly's CNS clock & Tac32Plus, yes?
Rick continues to develop the CNS clock, ha
Hi,
On 2021-02-27 17:18, Dana Whitlow wrote:
> Thanks, Bob.
>
> It seems to me that, depending on the positions of sats visible to one's GPS
> antenna and the spatial distribution of free electron density in the
> ionosphere,
> the ionospheric contribution to position errors could sometimes largel
On 2/27/21 8:18 AM, Dana Whitlow wrote:
Thanks, Bob.
It seems to me that, depending on the positions of sats visible to one's GPS
antenna and the spatial distribution of free electron density in the
ionosphere,
the ionospheric contribution to position errors could sometimes largely
cancel.
But t
Thanks, Bob.
It seems to me that, depending on the positions of sats visible to one's GPS
antenna and the spatial distribution of free electron density in the
ionosphere,
the ionospheric contribution to position errors could sometimes largely
cancel.
But that observation may (or may not) reflect s
Hi
> On Feb 27, 2021, at 9:41 AM, Dana Whitlow wrote:
>
> I've long understood that ionospheric delays and variations thereof lead to
> *position*
> uncertainties in GPS navigation receivers, to the tune of perhaps 10m
> (2DRMS IIRC).,
> and that these are said to constitute the single largest
I've long understood that ionospheric delays and variations thereof lead to
*position*
uncertainties in GPS navigation receivers, to the tune of perhaps 10m
(2DRMS IIRC).,
and that these are said to constitute the single largest GPS error source.
Q1: Would this not imply timing errors of comparabl
Hi
The same 20 or so ns delay in a saw would also apply to the
saw (or tight filter) in some timing antennas. It also would apply
to the saw(s) in some modules. Even if the tolerance is “only”
a couple ns on each of them, you *could* have 3 or more in the
chain.
Lots of numbers to crunch to get
A while ago I tried doing a decidedly non-anechoic measurement with a
VNA exciter going to a 1500 MHz ground plane and the receiver connected
to the antenna (with a known delay cable) and I got a similar result,
but there was enough noise that I didn't think I could nail it down to
within 10 ns
On 2/26/21 4:00 PM, John Ackermann N8UR wrote:
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 d
Typical L1 antenna delays range from 20 to 70 ns.
I know of only one antenna for which a delay is given by the vendor and the
technique used was just to measure the electronic delay ie by injecting a
signal into the circuit. To do it properly, you need a setup in a microwave
anechoic chamber with t
That's how I'd interpret it.
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On Feb 26, 2021, 7:42 PM, at 7:42 PM, Bob kb8tq wrote:
>Hi
>
>Would not “absolute” timing be referenced to UTC? (or something
>similar)
>
>Bob
>
>> On Feb 26, 2021, at 5:37 PM, ed breya wrote:
>>
>> John, if you look back at the recent G
You have to be careful comparing the LEA-M8F with other GPS units. It
does have low jitter because the "TIMEPULSE" signal is derived from the
TCXO which is locked to the GPS time mark.
But their claim of "essentially jitter free" depends on your definition
of "essentially" -- attached is a co
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
Hi
Would not “absolute” timing be referenced to UTC? (or something similar)
Bob
> On Feb 26, 2021, at 5:37 PM, ed breya wrote:
>
> John, if you look back at the recent GPSDO discussion initiated by "dandober"
> in hpaligent keysight group, you'll see a post by Leo Bodnar, linking a Ublox
> m
John, if you look back at the recent GPSDO discussion initiated by
"dandober" in hpaligent keysight group, you'll see a post by Leo Bodnar,
linking a Ublox model here
https://www.u-blox.com/sites/default/files/products/documents/LEA-M8F_DataSheet_%28UBX-14001772%29.pdf
I looked it up, and I re
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 ac
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
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