Re: [gpsd-dev] Off-topic but...

[Gary E. Miller]

Yo Gerry!

On Fri, 9 Feb 2018 13:34:17 -0600
Gerry Creager - NOAA Affiliate <address@hidden> wrote:

> Yeah, I'm familiar with the standard geodetic hardware, especially
> the old stuff. In fact, I'm looking at an old Ashtech right now.
> Javad at least used to be a solid innovator; Trimble's preamps were
> known to introduce their own interference when I started playing with
> 'em because of too much gain right at the antenna!

Well then, if you are going to be that picky, you should prolly head
over to time-nuts:

http://www.leapsecond.com/time-nuts.htm

Those guys argue about pico-seconds, and what time of year to buy
crystals because the one made in summer and fall are inferior.

> I'm more interested in modules and chip sets. I've found one site with
> several to choose from, but figured this group of experts might have
> already played with some of 'em if they existed.

For L1, I'm sure that is hardly a chip set that one of us does not have.
L1 is more than accurate enough for our purposes.  We seem to be stuck
around 500 nano seconds precision at best.  Although with RTK we can get
to cm measurements, our accuracy limited to a few meters.

L2 gets more expensive, and requires time-nuts to see the better than
nano second precision they provide.

I think the time-nuts with budgets are going for used/new cell tower
GPSDO.  They talk of 10e-12 frequency stability.  Way past my
budget, and need.

> What I want to do is be able to use carrier phase differentials for
> scintillation and water vapor (wet-delay) estimation. Of course,
> timing will just fall out without much work, too.

Oh, then time-nuts is definitely for you!  Just yesterday they were
arguing about the effects of 2 mm of water on signal propogation through
a GPS antennas.  Also yesterday they were talking about pulser kits
with 20 ps edge rise times, and with 10GHz sidebands, used for high
precision meaasurements.

Be sure to tell tvb I sent you.  Or maybe better not.  :-)

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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    "If you can’t measure it, you can’t improve it." - Lord Kelvin

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