Re: gpsrinex and Trimble

[John Ackermann N8UR]

Hi Gerry --

Good question.

The antenna is engineered, I hope, to make the best of a mediocre
situation.  Unfortunately for this purpose (and UHF contesting), my
house is on a quite wooded lo with nearby tall trees in just about every
direction.

The antenna is a Trimble Zephyr Geodetic.  To get a better sky view,
it's mounted on a very stiff (1/4 inch thick aluminum channel) side arm
that extends about 30 inches out from both sides of a Rohn 45G tower at
about 10 feet above the roof of the house.  There's only another 20 feet
of tower above that, and the antennas are pretty small, so while there
may be some twist in strong winds, I don't think it's very substantial.


The feedline is about 60 feet of LMR-400 going to a couple of HP
8-channel distribution amp/splitters, one with filters removed so it's
not limited to L1.

The worst tree cover is to the north, where thankfully it does the least
harm.  The trees in other directions are a bit more distant.

There's a Chinese L1/L2/L5 antenna on the other end of the side-arm so I
can do base and rover tests without leaving home. :-)  And actually
doing that gave me a *very* accurate bearing for the sidearm which means
sooner or later I'll get the Zephyr fiducial mark aligned more
accurately to north (it could well be 15 or 20 degrees off now).

I need to do some experiments now that the leaves are coming out, but I
suspect I should be running with an elevation mask quite a bit higher
than the default 7.5 degrees.

John
----

On 5/5/20 5:29 PM, Gerry Creager - NOAA Affiliate wrote:
> Yo, I believe is the appropriate salutation; it's been a long COVID...
> First, a question for John: What was the antenna and where was it
> (indoors, outdoors, sitting on a pvc pole waving in the wind?
> 
> On Tue, May 5, 2020 at 8:23 PM Gary E. Miller <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     Yo John!
> 
>     On Tue, 5 May 2020 16:15:06 -0400
>     John Ackermann N8UR <address@hidden <mailto:address@hidden>> wrote:
> 
>     > Well, I was actually able to get TrimbleRTX to accept my F9P RINEX
>     > file created by gpsrinex.
> 
> 
>     Good.  Someone reported otherwise this week.
> 
>     > It would *not* accept the one created by
>     > rtklib's convbin tool -- no useful explanation what was wrong, just
>     > unrecognized file format.
> 
>     Those are called "Lassie Errors".  Content free.
> 
>     Does anyone here have Timb;e contacts?
> 
>  
> Not anymore, thankfully but let me reach out to someone who might. 
> 
> 
>     > The bad news is that the results were pretty awful.  Since the results
>     > are just a single-page PDF, I've attached it here.  But in summary:
>     >
>     > Out of 2873 total observations, 100% were usable, but only 207 (7%)
>     > were used.  That raises a lot more questions than it answers...
> 
> 
> A couple thoughts
> 
>   * Antenna wasn't stable
>   * Multipath due to an inadequate antenna
>   * Misrepresented as static which tightens the error criteria
>   * Trimble is sometimes obnoxious in its interpretations 
> 
>     No thanks.  We already have enough unanswetred questions here.  :-)
> 
>     > The sigmas (not clear if 1 or 2 stdevs) are 0.185m, 0.131m, and 0.066m
>     > for XYZ, and 0.062m, 0.195m, and 0.130m for lat/lon/height.  The
>     > report came with this warning:
> 
>  
> 1 sigma; Top of the column...
>  
> 
>     Which are about 10x worse than NRCan.
> 
>     > Of course, those numbers don't actually appear in the report itself.
> 
>     Typical Trimble.
> 
> 
> What he said
> 
> gerry
>  
> 
>     RGDS
>     GARY
>     
> ---------------------------------------------------------------------------
>     Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>             address@hidden <mailto:address@hidden>  Tel:+1 541 382 8588
> 
>                 Veritas liberabit vos. -- Quid est veritas?
>         "If you can't measure it, you can't improve it." - Lord Kelvin
> 
> 
> 
> -- 
> Gerry Creager
> NSSL/CIMMS
> 405.325.6371
> ++++++++++++++++++++++
> /The way to get started is to quit talking and begin doing./
> /   Walt Disney/