Attila Kinali wrote:
On Thu, 28 Aug 2014 06:30:14 -0700
Bob Stewart <b...@evoria.net> wrote:
Is wood, nails, and asphalt shingle really that big of a problem at
these frequencies? The antenna is within 2 ft of the highest point
of the roof.
Consider this: A lot of people complain about the reflections caused
by trees. But what is a tree? It's mostly air and a few leaves, with
a branch here and there.
Also: 60cm is less than 2λ. ie the roof is in the near field of the
antenna, where everything causes a change of the antenna behaviour
(resonance frequency, radiation pattern, phase centre etc)
Depending on what you do with the GPS signal, you might or might
not care about that. If you are a nutty time-nut and want to
wring out ever last bit of jitter out of your PPS, then you
will care about the effect of the roof.
Attila Kinali
In light of these posts about antennae and reflections, etc., I have a
similar question. I'm planning to move my workbench out of my attached
garage into a separate garage building. The new garage is about 24' x 36',
and has a metal roof. My plan is to mount my GPS antenna atop a metal pipe
mounted at the peak at the end of the gable roof.
How far above the metal roof should I mount the antenna so reflections will
be minimized, at least to the point of diminishing returns?
The antenna will have a pretty good view of the sky from that location. Any
other issues that I should be aware of when dealing with a metal roof?
Thanks,
Dave M
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