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Re: moving to 8 digits of lat/lon (gpxlogger, maybe elsewhere)?

From: Gary E. Miller
Subject: Re: moving to 8 digits of lat/lon (gpxlogger, maybe elsewhere)?
Date: Thu, 3 Sep 2020 13:03:07 -0700

Yo John!

On Thu, 3 Sep 2020 15:46:03 -0400
John Ackermann N8UR <> wrote:

> On 9/3/20 3:29 PM, Gary E. Miller wrote:
> >> I'm using the u-blox ANN-MB-00-00 dual-freq mag mount antenna,
> >> which seems a bit touchy.  It absolutely wants a ground plane (I'm
> >> using a metal pie tin) and the solution often dropped to float
> >> when there were sky obstructions.  
> > 
> > Uh, wait a minute.  If the pie tin is > 50mm it is not doing what
> > you think it is doing.  See Section 5 of this u-blox doc:
> > 
> >      'GPS-Antenna_AppNote_(GPS-X-08014).pdf'  
> Thanks for the pointer to that.  Interestingly they don't talk about
> the effect of ground planes bigger than about 100mm square -- and a 
> vehicle-mounted mag mount is likely to have a much larger metal
> surface. I wonder how a several-wavelength ground plan impacts
> things...

gpsprof can answer those questions.

> Anyway, the pie tin was a temporary expedient, adopted when I found
> that without something under the antenna, I could get only a FLOAT
> soluton; adding the pie tin got me a FIX solution within a few
> seconds.

I'm not saying it does not work, just not the way you think it does.

Over-large ground planes limit reception from sats nar the horizon.
I suspect setting the elevation cutoff to a large value (30 degrees?)
may yield similar results.

> Once I figure out the best way to feed more than 3.3V  down the
> cable, I have a nice Ashtech survey antenna available for field use.

Easy, I use cheap chinese bias teess.  Like this one:

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

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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