I've done some quick research. I do not see timing as one of the services
provided. I wonder if it can be achieved by just listening into what's already
transmitted (like GPS) and do some math on our side.
On more broader sense, was GPS originally designed to provide timing service?
Or is it a byproduct of needing to measure location and speed, thus it needed a
constant signal, and that using it to sync reference signal is just an
ancillary and after-thought use cases?
---------------------------------------
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Sunday, August 9, 2020, 9:21:23 PM EDT, Bob kb8tq <kb...@n1k.org> wrote:
Hi
> On Aug 9, 2020, at 7:03 PM, Tom Van Baak <t...@leapsecond.com> wrote:
>
> Hi Stu,
>
> There's no problem with a semi-commercial posting here. You've been a member
> for a decade and frequent contributor plus the subject matter is exactly
> on-topic. So thanks for posting.
>
> I spent a while on your web site and didn't uncover a trove of white papers.
> If you could post some URL's that would be appreciated. You don't have to
> worry about being less accurate than GPS. I mean, there are often far more
> important factors than nanosecond precision.
To that point ( as accurate as GPS ) ….. GPS is simply a convent comparison
system. Saying that
this or that is better or worse at this or that tau is *not* the same as saying
it has more or less value.
It’s simply a system that is out there to be compared to.
Bob
> You didn't mention pricing; it's hard to imagine it's as free as GPS so that
> seems like another disadvantage to me.
>
> Your comment about fewer satellites is spot on. That will be taken care of if
> you give SpaceX / Starlink a call and join that bandwagon. There are already
> 597 Starlink [1] satellites up there vs. 82 Iridium [2] satellites, yes?
>
> If you have entry-level / hobbyist grade evaluation kits I'm sure a number of
> us would be very interested to try it out.
>
> Thanks,
> /tvb
>
> [1] https://en.wikipedia.org/wiki/Starlink
>
> [2] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
>
>
> On 8/9/2020 2:53 PM, Stewart Cobb wrote:
>> Taka Kamiya and Forrest Christian both asked recently about the alternative
>> satellite PNT system using the Iridium satellites. That system was
>> developed by my company, Satelles. It has been commercially available for
>> more than a year now.
>>
>> The biggest advantage is that our signal is at least 30 dB stronger than
>> GNSS signals (the exact numbers depend on whether you're talking to
>> engineering or marketing :). You can easily get a usable signal in deep
>> jungle, or a data center in the middle of a building's basement, or even
>> inside a locked shipping container. The stronger signal is correspondingly
>> more difficult to jam or spoof than GNSS, and our signal has anti-spoofing
>> features as well.
>>
>> The biggest disadvantage is that it is not quite as accurate as GPS,
>> because there are fewer satellites in view at any given time.
>>
>> I don't want to quote exact timing numbers here, because they depend a lot
>> on system integration details, but you can easily steer an OCXO within a
>> few hundred nanoseconds of USNO time. With a rubidium, you can do
>> considerably better.
>>
>> If you want to know more, our website is www.satellesinc.com.
>>
>> (If this message has been too commercial, I apologize in advance. The
>> boundary between information and salesmanship is not always sharp.)
>>
>> Cheers!
>> --Stu
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>
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