[time-nuts] GPS antenna selection

["Björn Gabrielsson"]

>> The real question is how much of a sky view you get.
>
>> Ideally you would like a clear view of the sky from
>> about NE clear around to NW (270 degrees).
>
> That would opt for the balcony, as it faces north
> and extends the slanted roof, so basically clear
> view from NE to NW down to the horizon.
>

Take a look at (yes M$ Silverlight is needed...:( )

     http://www.gnssplanningonline.com/

On "Settings" enter
    1) your position (lat, lon, h) - or chose approx position from map.
    2) change "cutoff" to 0 deg
    3) change "Time span" to max (24h).

On "Satellite library"
    1) Disable Glonass, Galileo, BeiDou and QZSS (only GPS remain selected)

Then view "Sky Plot". This is an illustration where the satellites can be
seen by your antenna, with no blocking from house, trees, mountains etc.
The blue outer circle represents the horizon, north up, etc. Circle center
is straigt up into the sky. The fainter grey circles shows 30 and 60 deg
elevation from the horizon.

    - Moving the time-ruler (lower-right corner) will show the satellites
move over the selected position.
    - While moving the time-ruler around, notice that there is a circle
from north horizon:ish and down (with a latitude of ca N45deg, where
there are never any satellites.
    - Where this circle is depends on your latitude.  (check N90deg -north
pole and N0deg (equator) to get a feel of how the priority
directions(azimuth)/elevations are.

You can model your specific obstruction environment at different possible
antenna sites with "Settings" -> "Obstructions".

What is an obstruction? it depends, but first order approx is that
anything that blocks your view will count.

What kind of GPS-receivers will you use? Old receivers (10+years) will
need better installations/locations. Modern high sensitivity receivers
will work decently within many houses. For long cable runs, older receiver
will be more picky, etc.

Good luck!

--

    Björn