[time-nuts] Mounting GPS Antenna on Steel Roof

Matthew Smith matt at smiffytech.com
Tue Mar 4 00:08:24 EST 2008


Hi Folks

Further to the cable splicing thread, I have been having a discussions
off-list with Didier regarding the placement of my antennas on the ridge
cap of my roof.

There is certain concern that I may have issues with reflections - can
anyone confirm whether or not this is the case?

Here is a terrible diagram (I cannot for the life of me figure out how
to draw solid, straight lines with the Gimp) of the proposed installation:

<http://www.smiffysplace.com/files/antenna_diagram.jpg>

The ridge runs just about 15 degrees of an East-West line, is the
highest ridge on the building and is the highest point for some distance
(there are trees 80m to the South), barring a vertical phased array VHF
TV antenna.

I can't really see how a signal striking the roof would reach the
antenna, working on the basis of angle of refection = angle of incidence.

Is this installation likely to case me any problems?  I am rather short
on other options due to the presence of steel sheds and fences.  Getting
the antenna clear of all of these would probably require something like
a 100m+ cable, either buried or strung overhead, neither of which is
practical (nor the cable length).

The cable run from the ridge to my office works out at about 10m.  I
will have a redundant antenna a couple of metres along the ridge from
the main, disconnected.  If antenna #1 were to fail, I would just unplug
the antenna extension cable in the loft from #1 and connect to antenna #2.

I have spotted a splitter on eBay that is good for 10-1880MHz and
includes power passing on one output - I guess that this means I am
still able to power the active antenna as normal provided that at a
receiver is connected to that output.

Any comments on this would be much appreciated.

Cheers

M

-- 
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
LinkedIn: http://www.linkedin.com/in/smiffy



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