[ntp:questions] Roof antenna, which one, would you bother?

Rob nomail at example.com
Fri Jan 3 12:37:14 UTC 2014

Ralph Aichinger <ralph at pangea.at> wrote:
> I am currently in the process of remodeling my house
> and a dedicated outdoor/roof mounted GPS antenna
> would be possible to mount without excessive cost.
> I probably would not see a huge difference for
> timing purposes, but what would your choice of 
> an outdoor GPS antenna/receiver be? I am planning
> to put the NTP server (small Raspberry Pi, nothing
> fancy) into a rack maybe 10 metres of cable length away 
> from the roof. Or would you move the NTP host itself
> to the attic and run Ethernet up?

I use a generic (no brand) GPS magnetic antenna probably designed
for use on a car roof.  Not sure if they are still available, it
seems like most GPS receivers today work inside a car anyway.
The antenna comes with about 3 meters of very thin coax, which I
run indoor.  The antenna is stuck on a metal strip that is part
of the roof lining (of course first check the metal type, it will
not stick on most metals used for that purpose, but here it does)

The GPS receiver is inside.  In my case I run RS232 to the also
nearby computer.  But in case of a Pi I would combine the Pi and
receiver in a small box mounted inside, and the antenna outside,
whenever possible.  10 meters of cable is a bit much at the frequency
of GPS and typical cable used, I would go for UTP to cover that
distance when you can still keep the Pi inside.  When that is
not practical I would try extending the antenna cable.

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