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S o n o m a U s e r M a n u a l
I N S T A L L I N G T H E G P S A N T E N N A
Mounting Inside
A Window
For GPS time servers, it is possible to mount the GPS antenna inside a window and have it perform
adequately. Avoid windows with metallic film coating that will inhibit GPS signals and ensure that
the window has a good view of the sky. If you are in the Northern hemisphere, then a south-facing
window is best and in the Southern hemisphere, the opposite is true.
Your Sonoma needs to calculate its position in order to operate properly. It only needs to do this
once, but it requires that four satellites are visible at least some of the time. If your Sonoma has
a limited view of the sky, it may not be able to see the required four satellites, so you will need to
manually enter your position. See
Obtaining a Reference Position
below for instructions.
Because of the reduced sky visibility that is characteristic of a window-mount installation, your time
server may go through many hours without locking to a GPS signal. This is fine, as long as it locks
for 10-15 minutes at least once every 24 hours. If the time server goes longer than 24 hours without
locking, then it will stop serving Stratum 1 time. An OCXO upgrade will allow the time server to go
for 35 days without receiving a GPS signal and is extra insurance for window-mount installations.
A window-mount antenna kit is available from EndRun.
Obtaining A
Reference Position
Your Sonoma is capable of operation from either an automatically determined GPS reference position
or a manually entered GPS reference position. If you need to provide a reference position to your So-
noma because you are using a window-mounted antenna with inadequate satellite visibility, there are
two good ways to do it: 1) use a handheld GPS receiver to obtain a position near the location of your
Sonoma antenna or 2) reference a geodetic (World Geodetic Survey of 1984 (WGS-84)) database to
obtain a position for your street address.
Using a Handheld GPS Receiver
Obtain an inexpensive, handheld GPS receiver. Use it outside of the building to determine a position
that is within 100 meters of the installed Sonoma antenna. Make sure that the handheld GPS receiver
is configured to report its positions in the WGS-84 datum. Record the position and then make any
adjustments to the height that might be necessary if the antenna is installed in a high-rise building.
Input it to the Sonoma via the
setgpsrefpos
command.
Using the Internet
Reasonably accurate position information can be obtained from various websites on the Internet.
Using your favorite search engine, type in a search term such as: “street gps position”. Many of the
websites displayed will give you the ability to type in your location and provide your GPS position
coordinates. The position needs to be accurate, to within 100 meters of the actual antenna location.
If you are unable to obtain a GPS ellipsoidal height (WGS-84) then you can do that by following the
instructions in
About WGS-84 Height
below.
Summary of Contents for Sonoma N12
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