[time-nuts] Roof Penetrations for a GPS Antenna Lead

Chuck Harris cfharris at erols.com
Tue Apr 1 23:37:34 EDT 2008

Stan, W1LE wrote:
> Hello The Net:
> I am also pondering adding a commercial GPS antenna on the roof at a height
> to locate the bottom of the antenna to just clear the ridge line.
> Choices I have addressed for my sloped and shingled roof:
> 1. Secure the antenna to an existing roof penetration, like a drain pipe
> vent for the shack bathroom. Snake the coaxial cable down the vent pipe,
> cut the drain pipe inside the attic and add a PVC tee section, allowing the
> coax to come out the horizontal "tee" outlet. Seal as needed to keep 
> vent gasses outside.
> I do not suspect the vent gasses from the septic system to be corrosive 
> to a
> GPS antenna rated for outside installation.

The gases are very bad, don't mess with your plumbing system!

Mount the antenna on the gable side of your roof, and bring it
through the gable.  Put a drip loop in the cable, and stuff the
hole through the gable with permagum.

Going through the ridge vent is also a good way to get inside.

Bear in mind that you are increasing the lightning profile of
your house by bringing a ground up to the peak of the roof.  If
you don't already have a lightning rod system, you probably should
add one, with a very tall rod that extends 5 or 6 feet higher than
your GPS antenna, and is within 5 feet of the antenna.

-Chuck Harris

More information about the time-nuts mailing list