[ntp:questions] (no subject)

Chris Albertson albertson.chris at gmail.com
Sun Sep 11 19:01:56 UTC 2011

2011/9/11 Miguel Gonçalves <mail at miguelgoncalves.com>:
> Hi!!
> My Motorola Oncore UT+ is working fine and I am using a cheap magnetic antenna.
> I want now to buy a better quality antenna for outdoor use.
> Any suggestions?

Any of the "timing antenna" are good.   Maybe they are better because
they are a helix type antenna but the most important part is the shape
of the plastic radome.  It's pointed so snow and bird poop does not
accumulate.  Also they are all designed to mound to a standard pipe
 so you can use a length of 1" galvanized pipe as a mast and run the
cable down inside the pipe.   Be sure and ground the pipe and add a
lightening arrester to the cable run

Look on eBay for "lucent GPS Timing Reference Antenna 26db Gain"
Expect to pay about $25, more or less plus ship.  and it you are
willing to drill some hole inn the pipe flange they mount to a
standard hardware store $4 part.  Otherwize you can spend $$ on a
custom stainless steel mount.  Also you really do want a good cable
with a "N" type connector and not adapters.  The N type is waterproof
and uses o-rings.  After you get the cable indoors use whatever
connectors you like but N is best for outdoors

That said.  I thin there are better antenna that have higher gain and
can drive a longer cable,  Here is one example
ebay #180721168817

But the Lucent parts are very common and cheap and you can always
place the UT+ close to the antenna, maybe right after the antenna lead
enters the building.   That is what I did, then I run cat-5 wire to
carry the PPS and serial line to the computer.  Antenna lead cable has
so many dB per door of loss.  You have to look it up for your cable.
For longer runs (like 50 to 100 feet) you can get low-loss cable but
the stuff is expensive.

It's an exercise in trade offs.  Get a higher gain antenna and be able
to drive lower cost or longer cable, use a short cable and cheaper
antenna.   As long as the gain at the GPS receiver is within spec you
care OK, the UT+ does not care how you do it.  The big advantage of
the timing antenna is that you cam place it high on a mast and being
pointed "stuff" slides off.

You will need  to measure or estimate the cable delays

Chris Albertson
Redondo Beach, California

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